home Thyroid Tuberculosis of farm animals. Animal tuberculosis: in cattle, horses, pigs, sheep and goats, birds, dogs, cats, camels, fur-bearing animals. Pathogen, course and symptoms, diagnosis, prevention and treatment

Tuberculosis of farm animals. Animal tuberculosis: in cattle, horses, pigs, sheep and goats, birds, dogs, cats, camels, fur-bearing animals. Pathogen, course and symptoms, diagnosis, prevention and treatment

Tuberculosis (Tuberculosis) is an infectious, predominantly chronic disease of many species of agricultural and wild animals, including fur-bearing animals and poultry, characterized by the formation of various organs specific nodules - tubercles, prone to cheesy disintegration.

Historical reference

Tuberculosis has been known since ancient times. Clinical signs of the disease in humans were described by Hippocrates in the 4th century. BC e. The term “tuberculosis” was first used by the French physician Lennec (1819), and the contagiousness of the disease was proven by J. A. Villemin (1865). The causative agent of tuberculosis was discovered by R. Koch (1882), and he also produced tuberculin in 1890. Russian researcher X. I. Gelman proposed tuberculin in 1888, but published the work only in 1892. In 1924, Calmette and Guerin produced the BCG vaccine to prevent tuberculosis in humans.

Animal tuberculosis is registered in many countries around the world. In most European countries it has been practically eliminated.

A great contribution to the study of tuberculosis and the development of health measures was made by S. N. Vyshelessky, P. P. Vishnevsky, M. K. Yuskovets, I. V. Poddubsky, V. I. Rotov, A. V. Akulov, N. A. Naletov and others.

The causative agent is a microorganism of the genus Mycobacterium. There are three main types of tuberculosis pathogens:

1) M. tuberculosis (human species);

2) M, bovis (bovine species);

3) M. avium (avian).

In terms of morphology and cultural properties, they are largely similar to each other; these are thin, straight, often slightly curved rods 0.8-5.5 µm long, located singly or in groups in smears. Branched, filamentous and coccus-like forms of the microbe are also found. The microbial cell membrane contains fatty wax-like substances, and granularity is noted in the protoplasm. Mycobacteria are strict aerobes, nonmotile, do not form spores or capsules, acid-alcohol-resistant; are stained by the Ziehl-Neelsen method in bright red, and other microflora are stained blue (color table I, L).

To grow the causative agent of tuberculosis, glycerin MPA, MPb, potatoes, egg and synthetic media are used. Cultures grow slowly of mycobacteria of the human species - 20-30 days, bovine species - 20-60, avian - 11 - 15 days. If there is no growth, it is recommended to keep the crops in a thermostat for 3 months. Pathogenicity individual species The causative agent of tuberculosis is not the same for different species of animals and humans. So, people are most sensitive to the pathogen of the human species; pigs, cats, dogs, cattle, fur-bearing animals are also susceptible, but birds do not get sick! (except parrots). All farm and wild animals, including fur-bearing animals, as well as humans, are sensitive to the bovine pathogen, but birds are immune. Birds and pigs are sensitive to the avian pathogen, and very rarely other mammals - animals and humans - become infected with it. Animals infected with avian mycobacteria may respond to mammalian tuberculin.

The species of the causative agent of tuberculosis is determined by the characteristics of their growth on artificial nutrient media and by performing a bioassay on guinea pigs, rabbits and chickens.

Differentiation of the species of the causative agent of tuberculosis in a bioassay.

Sustainability

Mycobacteria are very resistant to various environmental factors and chemicals. This property is explained by the presence of fatty wax substances in the microbial cell.

The causative agent of tuberculosis remains viable in manure for 7 months, in dried cow feces for up to a year, in soil for more than two years, in river water for up to 2 months; in meat, frozen and stored in the refrigerator - up to a year, in salted meat - 45-60 days, in butter - up to 45, in cheese - 45-100, in milk - up to 10 days. Pasture areas where animals with tuberculosis were grazed remain infected throughout summer period(V.N. Kislenko, 1972).

Heating milk to 70°C kills the tuberculosis pathogen in 10 minutes, and boiling it in 3-5 minutes. The best disinfectants are an alkaline 3% solution of formaldehyde (exposure 1 hour), a suspension of bleach containing 5% active chlorine, a 10% solution of iodine monochloride and a 20% suspension of freshly slaked lime, applied by three times whitewashing with an interval of 1 hour.

In addition to the pathogenic mycobacteria of the three named types of the causative agent of tuberculosis (pathogenic mycobacteria), the genus Mycobacterium contains a large group of atypical mycobacteria. Based on morphological characteristics, they are difficult to distinguish from the causative agent of tuberculosis; they are often represented by coarser, thicker, non-granular rods of different lengths. Atypical mycobacteria are widespread in nature, and many of them are saprophytes. Once in the body of animals, atypical mycobacteria are able to multiply in it, and create short-term sensitization of the body to tuberculin for mammals.

Epizootological data

Many species of domestic and wild animals are susceptible to tuberculosis, including game animals and birds (more than 55 species of mammals and about 25 species of birds). Most often this disease is recorded in large cattle, pigs, minks and chickens; less often - in goats, dogs, ducks and geese; very rarely - in sheep, horses and cats. Monkeys are highly susceptible to tuberculosis. Among wild ungulates, deer are more often affected. Humans also suffer from tuberculosis.

The source of the infectious agent is animals with tuberculosis, from whose bodies the pathogen is excreted in milk, feces, nasal discharge, and sometimes with sperm. When cows are infected with any type of tuberculosis pathogen, mycobacteria are always excreted in the milk.

Transmission factors for the causative agent of tuberculosis can be feed, water, pastures, bedding, manure, etc., contaminated with secretions of sick animals. Young animals are mainly infected through milk and skim milk obtained from sick animals. Intrauterine infection of calves is possible. Animals can become infected with the human species through contact with people with tuberculosis.

The route of infection is predominantly alimentary, but aerogenic is not excluded, especially when patients are kept together with healthy people in closed, poorly ventilated, damp rooms. Pigs often become ill when fed raw kitchen waste, as well as through contact with birds sick with tuberculosis. Birds become infected through nutritional means, but transovarial transmission of tuberculosis has also been established in chickens. Sick birds lay infected eggs. When infected eggs are incubated, many embryos die, and some of the hatched chickens become a source of the tuberculosis pathogen. Wild birds can be carriers of all three types of tuberculosis pathogen.

Tuberculosis spreads relatively slowly among animals. This is due to the duration incubation period illness (up to 45 days). Inadequate feeding, unsatisfactory living conditions (overcrowding, dampness) and other unfavorable factors reduce the overall resistance of the animal's body and contribute to the rapid spread of the disease. There is no definite seasonality in the manifestation of the epizootic process in tuberculosis. However, in cattle it is more often recorded during the stall period.

Pathogenesis

The causative agent of tuberculosis, having entered the body through digestive tract with food or inhaled air, penetrates the lungs or other organs. At the site of its localization it develops inflammatory process, manifested by cellular proliferation and exudation; There is an accumulation of multinucleated giant and epithelioid cells surrounded by a dense layer of lymphoid cells. The exudate accumulated between the cells coagulates, forming a network of fibrin, and an avascular tuberculous nodule is formed - tubercle. It initially has a grayish color and a round shape; its size is from the head of a pin to the size of a lentil grain. Soon the nodule is surrounded by a connective tissue capsule. Tissue within an encapsulated nodule due to lack of inflow nutrients and under the influence of the pathogen’s toxins it dies and turns into a dry, crumbly mass resembling cottage cheese (caseosis).

If a primary tuberculous nodule develops only at the site of entry of the pathogen (lungs, intestines), then such a fresh, isolated focus is called the primary effect. From there, the pathogen usually travels through the lymph flow to the regional lymph node, where pathological changes also develop. Simultaneous damage to an organ and a regional lymph node is called a complete primary complex. If the process develops only in the regional lymph node, then it is called an incomplete primary complex.

In a benign course of the disease, the primary focus undergoes calcification, a dense connective tissue capsule forms around it, and further development of the infectious process stops. In an organism with reduced resistance, the process of encapsulation of the pathogen in the primary focus is weakly expressed. Due to insufficient regeneration connective tissue the walls of the tuberculous nodule melt, and mycobacteria enter healthy tissue, which leads to the formation of many small, translucent nodules (miliary tuberculosis). Small tubercles can merge with each other, forming large tuberculous foci.

Mycobacteria from tuberculosis foci can enter the blood, which leads to the generalization of the process and the development of tuberculosis foci of different sizes in various organs (liver, spleen, kidneys, etc.). With a long course of the disease, large tuberculosis foci and cavities can form in the lungs, sometimes reaching the size of a fist. A dense connective tissue capsule grows around them. Tuberculous cavities can communicate with the lumen of the bronchi. In such cases, their contents liquefy and are released when coughing with sputum.

In the generalized form of tuberculosis and extensive lesions in the lungs, gas exchange is disrupted, srithropoiesis is inhibited, anemia is observed, productivity decreases, exhaustion and death of the animal occur.

Course and symptoms

Tuberculosis usually occurs chronically, and often without clearly visible signs. A positive reaction to tuberculin in animals occurs on the 14-40th day after infection (incubation period). Most animals with tuberculosis are no different from healthy ones in appearance and general condition, especially at the onset of the disease. Sick animals are identified mainly by allergic and serological testing; tuberculosis lesions are usually detected only during post-mortem examination of organs. As a result of systematic planned examinations of livestock (tuberculinization), it is possible to identify the disease in the initial stage. The appearance of clinically pronounced forms of tuberculosis indicates a long course of the disease.

Based on the location of the pathological process, pulmonary and intestinal forms of tuberculosis are distinguished; There are also lesions of the udder and serous integument (pearl oyster), the genital form and generalized tuberculosis.

It is conventionally accepted to distinguish between open (active) tuberculosis, when the causative agent of the disease is released into the external environment with milk, feces, sputum when coughing, and closed (latent) in the presence of encapsulated foci without the release of the pathogen into the external environment. If the intestines, mammary gland, or uterus are affected, the process is always considered open. In cattle, tuberculosis most often affects the lungs. If they are severely affected, a slight increase in body temperature is observed, rare, but coughing; with a protracted course of the disease, the cough becomes weak, silent, but painful. Expectoration is almost not observed in livestock; the bronchial mucus released during coughing is swallowed or excreted through the nose. In sick animals, shortness of breath, decreased appetite, fatness and productivity are noted.

Visible mucous membranes are anemic. Auscultation of the lungs reveals wheezing, and percussion reveals areas of dullness. Intestinal damage, which is accompanied by diarrhea, is accompanied by rapid exhaustion and increasing weakness of the sick animal.

Damage to the mammary gland is characterized by an enlargement of the suprauterine lymph nodes, which become dense, lumpy, and inactive. In the affected lobes of the udder, compacted painless foci are felt; with significant damage, the configuration of the affected lobe changes. When milking, watery milk mixed with blood or curdled mass is released. When the genital organs are affected, cows experience increased estrus and barrenness, and bulls experience orchitis.

In generalized tuberculosis, superficially located lymph nodes (submandibular, prescapular, knee fold, suprauterine) are inactive.

Tuberculosis in pigs is asymptomatic. Sometimes an increase in the submandibular and retropharyngeal lymph nodes is observed. Abscesses may appear in the affected nodes, after opening which a purulent-curdled mass is released. With extensive lung damage, coughing, vomiting, and difficulty breathing occur. Sheep and goats suffer from tuberculosis rarely and asymptomatically. With a highly expressed process, clinical signs are similar to those in cattle.

Tuberculosis in birds is chronic, with unclear clinical signs. The generalized form is accompanied by lethargy, decreased egg production, exhaustion (atrophy pectoral muscles). When the intestines are damaged, diarrhea is observed; liver - icteric staining of the mucous membranes and skin. Lameness and tumor-like formations on the plantar surface of the extremities are sometimes noted.

Among fur-bearing animals (foxes, mink, nutria), young animals are more often affected by tuberculosis. Patients experience weakness and progressive exhaustion; in the pulmonary form, cough and shortness of breath. Damage to the intestines is accompanied by diarrhea, and the liver is accompanied by icteric staining of the mucous membranes. Foxes sometimes develop long-lasting ulcers on their skin.

Pathological changes. Characteristic of tuberculosis is the presence in different organs and tissues of the animal of specific nodules (tubercles) the size of a millet grain to chicken egg and more. Tuberculous foci are surrounded by a connective tissue capsule, their contents resemble a dry, crumbly, curdled mass (caseous necrosis). With prolonged illness, tuberculous nodules may become calcified.

In ruminants, tuberculosis lesions are most often found in the lungs and lymph nodes of the chest cavity. In the lungs, dense, reddish-grayish lesions are found; on section they are shiny, sebaceous (no necrosis), often with caseosis in the center; sometimes the lesions have purulent foci. Occasionally, caverns of various sizes are found (cows, goats). Lymph nodes are most often affected. They are enlarged, dense, lumpy, with caseous tissue disintegration in the center of the node.

When the serous integument is affected, multiple (pearl oyster) dense, shiny tuberculous nodules, reaching the size of a hazelnut, are found on the pleura and peritoneum. The intestinal form of tuberculosis is manifested by round ulcers with roller-shaped edges on the mucous membrane of the jejunum and ileum.

In cattle suffering from tuberculosis, the lymph nodes of the chest cavity are affected in 100% of cases, the lungs - in 99, the liver - in 8, the spleen - in 5, the udder - in 3, the intestines - in 1% of cases (P.I. Kokurichev, 1950) . In pigs, tuberculous lesions are most often found in the lymph nodes of the mesentery and head and less often in the liver and other organs. In poultry they are localized mainly in the liver (90% of cases), spleen (70%), bones and intestines.

It is placed on the basis of an analysis of epizootic data, clinical signs and the results of allergic, serological (RSC with tuberculosis antigen), pathological, histological, bacteriological and biological studies. The clinical method for diagnosing tuberculosis is of limited value, since the clinical signs of the disease in animals are not typical enough, and at the onset of the disease they are not present at all.

The main method of intravital diagnosis of tuberculosis is an allergic study. For the study, tuberculin (allergen) is used - a sterile filtrate of killed cultures of the causative agent of tuberculosis. We prepare two types of tuberculin: dry purified tuberculin (PPD) for mammals and dry purified tuberculin SPD) for birds.

Dry purified tuberculin for mammals (protein purified derivative - PPD) consists of freeze-dried precipitated proteins from the cultural filtrate of the causative agent of bovine tuberculosis, grown on a synthetic nutrient medium. It is used for allergy diagnostics tuberculosis in all mammals.

Dry purified tuberculin (DPT) for birds is similar in appearance and manufacturing technology to DPT for mammals. It is prepared from the cultural filtrate of the causative agent of avian tuberculosis and is used to diagnose tuberculosis in birds and pigs.

Tuberculinization methods. The main method of intravital diagnosis of tuberculosis in animals is an allergic study using a tuberculin test. In horses, an eye examination method (ophthalmic test) is used. In some cases, in cattle it is placed simultaneously with intradermal.

As an additional method for diagnosing tuberculosis in cattle, a simultaneous allergy test is used, which is carried out simultaneously with purified tuberculin for mammals and a purified complex allergen from atypical mycobacteria (CAM).

Animals are tested for tuberculosis from 2 months of age; breeding stock of cattle, buffaloes and camels - regardless of the period of pregnancy; sheep, goats, pigs, deer (deer), horses and donkeys - no earlier than a month after birth.

Place of injection.

With the intradermal method of research, tuberculin is administered to: cattle, buffalos, zebu, deer (deer) in the middle third of the neck; for sires, it is allowed to inject into the skin of the subcaudal fold, for pigs - in the area outer surface auricle at a distance of 2 cm from its base (on one side of the auricle, PPD for mammals is introduced, on the other, PPD for birds). Pigs aged 2-6 months. It is better to inject tuberculin into the skin of the lumbar region, stepping back from the spine by 5-8 cm (tuberculin for mammals is injected on one side, and for birds on the other), using a needle-free injector of the IBV-01 brand. For goats, sheep, dogs, monkeys, fur-bearing animals (except minks), tuberculin is injected into the inner surface hips; mink - intrapalpebrally in upper eyelid; camels - in the skin abdominal wall in the groin area at the level of the ischial tuberosity; kuram—in the beard; for turkeys - in the submandibular earring; geese, ducks in the submandibular fold; pheasants, peacocks, parrots, pigeons, cranes, herons, storks, flamingos - in the area of the outer surface of the lower leg, 1-2 cm above the ankle joint. The fur at the site of tuberculin injection is cut (feathers are plucked), the skin is treated with 70% alcohol.

For tuberculinization, special needles for intradermal injections with a double tube (MRTU No. 46-84-62) or needles No. 0612 and syringes with a slider with a capacity of 1-2 ml are used. Needleless injectors are widely used to administer tuberculin to animals.

During intradermal tuberculinization, tuberculin is administered once in a volume of 0.2 ml to all mammals, except monkeys and minks, as well as birds (they are given a dose of 0.1 ml).

Accounting and evaluation of the reaction. In cattle, buffaloes, zebu, camels and deer, they are carried out 72 hours after administration of the drug; for goats, sheep, pigs, dogs, monkeys, fur-bearing animals - after 48; in birds - after 30-36 hours. The local reaction to the administration of tuberculin can be assessed as positive or negative.

Cattle, buffalo, zebu, camels and deer are considered tuberculin responsive if the above changes are present at the site of tuberculin injection and thickening skin fold by 3 mm or more compared with the thickness of the fold of unchanged skin near the site of tuberculin injection.

Sire bulls tuberculinized in the subcaudal fold are considered to react when an inflammatory swelling forms at the site of tuberculin injection and the skin fold thickens by 2 mm or more.

In goats, sheep, pigs, dogs, monkeys, fur-bearing animals and birds, the reaction is considered positive when a swelling forms at the site of tuberculin injection, and in minks - when the eyelid is swollen.

Intradermal tuberculin test is a highly specific reaction to tuberculosis. However, it depends on the general immunoreactivity of the body and the sensitivity of animals to tuberculin. In animals of low fatness, old, deep-pregnant animals, as well as with a generalized tuberculosis process, the reaction to tuberculin may be weakly expressed or not manifested (anergy). It should also be taken into account that nonspecific (paraallergic) reactions to tuberculin for mammals are sometimes possible, due to sensitization of the body by avian mycobacteria, pathogens of paratuberculosis and atypical mycobacteria, as well as other reasons. However, nonspecific reactions are unstable and disappear after a few months.

Rice. 1. Positive reaction to tuberculin: A - in a cow; B - pigs; B-birds

Differentiation of specific reactions from nonspecific ones in necessary cases a simultaneous test with avian tuberculin or a complex allergen from atypical mycobacteria (AM) and laboratory tests are carried out.

Tuberculinization by the eye method is carried out twice with an interval of 5-6 days. Tuberculin (3-5 drops) is applied with an eye dropper to the conjunctiva of the lower eyelid or to the cornea of the eye (with a retracted lower eyelid). The reaction is taken into account after the first injection after 6, 9, 12 and 24 hours, after the second - after 3, 6, 9 and 12 hours. It is considered positive if a discharge of mucopurulent or purulent secretion occurs from the inner corner of the eye, accompanied by hyperemia and swelling conjunctiva.

Allergy testing for animal tuberculosis is allowed to be carried out only by veterinary specialists who have undergone special course training, knowledge of the technique of administering diagnostic drugs and experience in assessing allergic reactions.

The diagnosis of tuberculosis is considered established: when a culture of the tuberculosis pathogen is isolated or when a positive result of a biological test is obtained. In cattle, in addition, the diagnosis is considered established when detected in the organs or tissues of animals pathological changes, typical for tuberculosis.

Upon receipt positive results Allergic studies for tuberculosis, diagnosis of the disease is carried out by slaughtering 3-5 animals with the most pronounced reactions to tuberculin and examining internal organs, bones and lymph nodes. In the absence of typical changes for tuberculosis, pieces of organs and lymph nodes are selected and sent to a veterinary laboratory for bacteriological examination.

All livestock of the herd, including previously reacting animals, are tested with a simultaneous test with tuberculin for mammals and the KAM allergen. In herds, on farms, in populated areas where the disease has already been established, animals that react to tuberculin are recognized as having tuberculosis.

Animals with tuberculosis are not treated and must be slaughtered. In disadvantaged fur farms, tubazid (isoniazid) is used to prevent tuberculosis in minks. The drug is given with food at a dose of 10 mg/kg of animal once a day for 75 days.

Immunity

In tuberculosis, it is non-sterile, remaining as long as mycobacteria are in the body. Phagocytosis is incomplete, and phagocytosed mycobacteria do not die. The body produces agglutinins and complement-fixing antibodies, but their role in immunity is insignificant. Protection is mainly determined by the body's ability to stop pathological process, limit the pathogen in granulomas-tubercules. For specific prevention of tuberculosis in young cattle and minks, the dry BCG vaccine used in medicine is used. Clinically healthy animals are vaccinated with it.

Prevention and control measures

Measures to combat tuberculosis include the protection of healthy farms from the introduction of the infectious agent from the outside, systematic research in order to timely identify sick animals, the improvement of farms unfavorable for tuberculosis by slaughtering sick animals, the isolated rearing of healthy young animals and the implementation of a set of veterinary, sanitary and organizational and economic measures, aimed at protecting healthy livestock and destroying the causative agent of tuberculosis in the external environment; protecting people from tuberculosis infection.

In safe farms, all measures should be aimed at protecting the farm from the introduction of the pathogen. For this purpose, farms are stocked with healthy animals from farms that are free from tuberculosis. Newly received animals are examined for tuberculosis during a 30-day quarantine period. Feed is purchased only from farms that are free from tuberculosis. The skim milk supplied for feeding young animals is pasteurized, and the collected food waste is subjected to heat treatment. Persons with tuberculosis are not allowed to serve animals, and poultry is not allowed to be kept on the premises. livestock farms. Periodically, preventive disinfection of livestock premises is carried out, rodents and ticks are destroyed, and measures are taken to improve the feeding and maintenance of animals. In breeding farms it is strictly prohibited to use peat for animal feed and bedding.

In order to timely identify animals with tuberculosis and monitor the welfare of farms with regard to this disease, planned annual diagnostic studies animals for tuberculosis. Cows, heifers and young cattle from 2 months of age, stud bulls, sows, boars, camels intended for sale for breeding purposes are examined.

Twice a year, cattle from breeding farms and farms supplying animals for stocking livestock complexes, milk and dairy products directly to children's and medical hospitals are tested for tuberculosis. medical institutions, rest homes or retail chains, as well as farms geographically bordering areas unfavorable for tuberculosis. Cattle belonging to citizens living on the territory of these farms are examined simultaneously with the farm livestock.

On breeding pig farms and in reproductive farms, sows are examined before weaning piglets, and boars - 2 times a year. In other farms, sows, boars and, if necessary, young animals from 2 months of age are examined once a year.

Monitoring the welfare of poultry and fur farms for tuberculosis is mainly carried out by inspection and pathological examination of dead and killed animals and birds, as well as by the allergic method. Horses, mules, donkeys and sheep are tested for tuberculosis on farms affected by this disease.

If tuberculosis occurs, the farm (farm) is declared unsafe, quarantine is established and a calendar plan of measures to eliminate the disease is drawn up.

In farms affected by tuberculosis in cattle, buffaloes and reacting animals, they are immediately isolated and slaughtered within 15 days. Young animals born from sick animals are fattened in isolated conditions and sent for slaughter. The remaining animals (not responding to tuberculin) of the unfavorable farm are tested for tuberculosis every 60 days until two negative results are obtained in a row for the group, after which two more control studies are carried out with an interval of 3 months. If negative results are obtained and there are no other indications for tuberculosis, this group of animals is considered healthy.

Calves born from animals from a dysfunctional farm that do not respond to tuberculin are raised in isolation and fed with the milk of healthy cows or neutralized milk (skim milk) of their mothers. At 2 months of age they are examined for tuberculosis using the intradermal method.

Calves that react positively to tuberculin are isolated and after fattening they are slaughtered. Non-responders are examined 2 more times with an interval of 60 days, then after 3 months. Upon receipt for the entire group negative result they are recognized as healthy and used for production purposes only within the farm.

The improvement of farms with significant livestock affected by tuberculosis (more than 25% of animals) is carried out by slaughtering unfavorable livestock.

The success of the fight against tuberculosis largely depends on the activities of farm managers, who are called upon to provide the necessary assistance to veterinary specialists in conducting diagnostic studies, disinfection work, implement a set of preventive measures aimed at creating a high sanitary culture in livestock farming, increasing the natural resistance of the animal body, and equipping veterinary facilities - sanitary purposes, strictly comply with the requirements of the instructions for combating the disease.

In areas unfavorable for tuberculosis, it is recommended to create special groups (detachments) of veterinary specialists to carry out work on mass testing of animals for tuberculosis.

Under the terms of quarantine, it is prohibited to keep animals sick with tuberculosis in herds and in common livestock buildings, as well as to organize any kind of temporary and permanent concentration points and isolation farms for keeping such animals on farms. In areas unfavorable for tuberculosis in cattle, it is not allowed to create off-farm complexes, farms and other enterprises for raising heifers. In all farms in such areas, on-farm farms (departments, teams, plots) should be organized for the isolated rearing of young animals. Livestock purchased by farms or consumer cooperation organizations from the population living in the territory of farms (settlements) unfavorable for tuberculosis are subject to immediate delivery for slaughter without fattening and fattening (in transit), regardless of weight standards.

It is prohibited to export undisinfected milk obtained from cows of a dysfunctional farm, farm, or herd in a populated area to milk processing plants, for sale in markets, or for use online. Catering etc. Such milk is subject to primary processing directly on the affected farm (on the farm) for the entire time until the disease is completely eliminated and quarantine is lifted. At the same time, milk obtained from cows with clinical manifestations of tuberculosis is prohibited from being used for food purposes and as animal feed. It is disinfected by adding 5% formaldehyde or another disinfectant to the milk. Given this, sick cows should not be milked. Milk from cows that react to tuberculosis during testing is disinfected by processing it into raw ghee or by boiling.

Dairy products from non-responsive cows of a dysfunctional herd are disinfected at a temperature of 90 C for 5 minutes or at a temperature of 85 ° C for 30 minutes.

Dairy enterprises must release skim milk to farms only after it has been disinfected by pasteurization or heat treatment with live steam.

In specialized complexes, on farms for raising heifers (heifers), when a disease is detected in young animals of the technological (age) group in which patients are identified, all heifers of this group are slaughtered within 30 days, the rest of the animal population of the complex, farm - within 6 months (no more). Insemination of heifers is prohibited. During the period of recovery, the introduction of heifers from supplying farms into the complex and onto the farm is stopped, and in the future, recruiting them as off-farm enterprises for raising heifers with new livestock is not allowed.

At beef production complexes and other fattening farms, when tuberculosis is diagnosed, all animals in the disadvantaged group are branded with the letter “T” and slaughtered within 15 days. The remaining livestock is examined every 60 days for tuberculosis using the allergic method or the issue of selling all the animals of the complex (farm) for meat is decided.

When infection of cattle with the causative agent of avian tuberculosis or atypical mycobacteria is established, and also when animals that react to tuberculin are detected in a free herd (on a farm), but tuberculosis has not been established in them by previous studies, the herd (farm) is considered free from tuberculosis.

In pig farms (on farms) where pigs have been infected with the causative agent of bovine tuberculosis or human species, all pigs that react to tuberculin (including pregnant sows), as well as boars and fattening livestock, are immediately slaughtered. The remaining sows that do not respond to tuberculin are sold for meat after farrowing, and young animals - after growing. On dysfunctional farms, insemination of sows is prohibited. The elimination of the outbreak of tuberculosis in pigs is carried out within no more than 6 months.

Horses are examined by an ophthalmic test. Reacting animals are sent for slaughter, and the rest of the livestock is examined every 60 days until a negative single result is obtained, on the basis of which the study group is recognized as free from tuberculosis.

Goats and sheep are examined with a tuberculin test. Those who respond are sent for slaughter, and the rest of the livestock is tested for tuberculosis every 60 days until a negative result is obtained for the group.

If deer (deer) in a disadvantaged herd become infected with tuberculosis, the animals are tested for tuberculosis until negative results are obtained for the herd. Animals that are clinically ill and react to tuberculin are sent for slaughter. Deer (red deer) are examined for tuberculosis in November - February (males additionally in July - August), and young animals - after they are transferred to winter roads.

When tuberculosis is established in dogs, animals reacting to tuberculin (females along with their offspring) are killed, and their skins are used without restrictions. In nurseries, animals from the disadvantaged group are tested with tuberculin every 60 days until negative single group results are obtained.

When tuberculosis is detected in fur-bearing animals, they are subjected to a clinical examination, sick animals (females along with their offspring) are isolated. During the period of skin maturation, they are fed daily tubazide in therapeutic dose(according to the instructions for its use). The animals are killed after the skins have matured, which are used without restrictions. For the remaining animals of the disadvantaged group (farm), tubazide is added to the feed in a prophylactic dose; minks in such a farm are vaccinated with the BCG vaccine for preventive purposes.

A fur farm (farm) is considered healthy if during one production period (from whelping to slaughter for skins) no changes typical for tuberculosis are found in the organs of dead and killed animals.

In poultry farms, when tuberculosis is diagnosed, all the birds in the affected poultry house (zone, workshop, department) are handed over for slaughter, veterinary and sanitary measures are carried out, and after the quarantine is lifted, a new flock of healthy pullets is formed. On dysfunctional farms, it is necessary to maintain cleanliness, carry out disinfection, disinfestation, deratization, sanitary repair of livestock premises and other veterinary and sanitary measures in accordance with current instructions.

For disinfection on farms, the following is used: a suspension or clarified solution of bleach; neutral calcium hypochlorite solution; hypochlorite or hexanite containing at least 5% active chlorine; drug DP-2; 1% aqueous solution of glutaraldehyde; alkaline formaldehyde solution containing 3% formaldehyde and 3% sodium hydroxide; 5% solution of technical sodium phenolate; 20% slurry of freshly slaked lime by whitewashing three times with an interval of 1 hour.

For aerosol disinfection of cleaned and hermetically sealed premises in the absence of animals, a 40% aqueous solution of formaldehyde is used.

The surface layer of soil is disinfected with 3% alkaline solution formaldehyde or bleach. Pasture areas on which herds unaffected by tuberculosis were grazed can be used after 2 months in the summer in the southern regions and 4 months in the rest.

Manure, bedding and food residues from animals sick or suspected of being sick or infected with tuberculosis are destroyed or disinfected by biological, chemical or physical methods.

A livestock farm (department), household, settlement is recognized as recovered from tuberculosis after the complete cessation of the disease in animals with this disease, delivery of all sick animals for slaughter, carrying out a set of final organizational, economic, veterinary and other measures provided for in the instructions for combating the disease. An act on this is drawn up, on the basis of which the main veterinarian district (city) submits to local authorities a proposal to remove tuberculosis quarantine from a disadvantaged point.

In farms recovered from tuberculosis, after the quarantine is lifted, restrictions on the sale of animals for breeding and production purposes and showing them at exhibitions, cattle broods for four years, and pigs for one year remain limited.

TUBERCULOSIS OF SMALL ANIMALS AND BIRDS
TUBERCULOSIS (Tuberculosis) is a chronic infectious disease characterized by the formation of tuberculosis in parenchymal organs, intestines and other tissues.
ETIOLOGY. The causative agent is a microbe belonging to the genus Mycobacterium, species: M. tuberculesis (human) and M. bovis cause disease in dogs, cats and fur-bearing animals; In rabbits and minks, tuberculosis is most often caused by mycobacteria of bovine and avian species. Mycobacterium avium is the causative agent of tuberculosis in birds. Parrots can become ill when infected with human mycobacteria.
Mycobacteria are thin, straight or slightly curved, immobile rods, acid- and alcohol-resistant, due to the presence of fatty wax-like substances in the shell. They do not form spores or capsules; they are strict aerobes and are cultivated on special nutrient media (Petragnani, Gelberg, etc.). It is stained bright red according to Ziehl-Neelsen, and the secondary microflora is stained blue.
M. avium grows at temperatures of 41-420 C.
They remain stable in soil for up to 5 years, in manure and litter for up to 1.5 years. Boiling causes inactivation in 3-5 minutes. The best disinfectants are a 3% alkaline solution of formaldehyde, a suspension of bleach containing 5% active chlorine, and a 20% suspension of freshly slaked lime with three times whitewashing.
EPISOOTOLOGICAL DATA. IN natural conditions Foxes, minks, arctic foxes, nutria, dogs and cats are susceptible to tuberculosis. Young nutria and mink are especially sensitive. Tuberculosis has not been recorded in sables. In rabbits, the disease is registered in the form of isolated cases in the presence of unfavorable conditions for tuberculosis in cattle and birds.
Of the birds, the most susceptible are chickens, less so turkeys, ducks, and geese. In total, about 25 species of birds are affected.
The source of the infectious agent is people with tuberculosis, animals and poultry from whose bodies the pathogen is excreted through nasal discharge, pulmonary sputum, milk, feces, urine and eggs.
Transmission factors include offal of animals and birds with tuberculosis; laid eggs, infected milk, feed, water, bedding, manure, equipment, etc.
The mechanical carriers of the pathogen are sparrows, pigeons and other wild birds, as well as rodents that eat the corpses of dead birds.
In carnivores, nutria and rabbits, the main route of infection is nutritional. Transmission of the pathogen by airborne routes cannot be ruled out. Puppies can become infected during the suckling period from a sick mother.
Sick minks have intrauterine infection of puppies. Animals can become infected through contact during mating.
In birds, infection is most often through the nutritional and transovarial routes.
There is no strict seasonality or periodicity, but there is a clearly defined stationarity. The incidence of tuberculosis can be 60-70%.
PATHOGENESIS. During alimentary infection, mycobacteria, entering the intestine, penetrate the mucous membrane and linger in the lymphofollicles of the intestinal wall. Here primary changes develop, expressed in hyperplasia of lymphofollicles and the formation of epithelioid tubercles.
From the intestine, mycobacteria penetrate through the lymphatic tract into the liver, where primary epithelioid tubercles also develop.
Primary changes in the lungs during aerogenic infection are of a similar nature. As the nodule develops, mycobacteria multiply in it, which leads to dystrophic changes. With a long course of the disease, large tuberculous foci and cavities can form in the lungs, and tuberculous pleurisy develops (especially in dogs and cats). In birds, in the early period of development, tubercles form conglomerates that have a common capsule.
With the progressive development of infection, the pathogen from primary foci spreads hematogenously, which leads to the formation of multiple tubercles in the organs, primarily in the liver, spleen, intestines, and lungs.
CLINICAL SIGNS AND COURSE. The duration of the incubation period (time from infection to the onset of an allergic reaction) for experimental infection is 15-17 days, clinical signs appear after 1-10 months. The disease is chronic.
Dogs show signs of damage to the lungs (shortness of breath, short, dry cough and nasal discharge) and gastrointestinal tract (vomiting, diarrhea).
In cats, severe emaciation, anemia, difficulty breathing, suppuration of the parotid, submandibular and prescapular lymph nodes are recorded. The skin on the head, neck, eyelids, bridge of the nose and cheeks is often affected in the form of fluctuating tumors containing a yellow, crumbly mass.
In young minks (15-20 days), tuberculosis occurs in the form of generalized damage to internal organs.
In foxes, arctic foxes and nutria, tuberculosis is less malignant. With pathology of the intestinal tract - vomiting, diarrhea, severe exhaustion. If the respiratory tract is affected - cough, wheezing, shortness of breath. If the liver is involved in the process - yellowness of the mucous membranes; nervous system- agitation, loss of vision, paresis and paralysis of the limbs.
In 5-7 month old fox puppies, one or both eyes are very often affected. Wherein eyeball increased in volume, protrudes from the orbit, and clouding of the cornea is observed. After 15-30 days, the eyeball opens and brown liquid flows out of it.
In rabbits, there are two forms of the disease: pulmonary (cough, rapid breathing, shortness of breath) and intestinal (decreased appetite, diarrhea and emaciation).
In birds, the first clinical signs are increased temperature, inactivity, decreased egg production, general weakness. A sick bird has a wrinkled comb and wattles, pale, visible mucous membranes and icteric skin. Diarrhea and lameness, swelling of the joints and plantar surfaces are often reported. Sometimes paresis and paralysis of the legs and sagging wings are noted. The sick bird loses weight rapidly and dies from complete exhaustion.
In turkeys, geese, ducks, and guinea fowl with tuberculosis, the symptoms of the disease are less pronounced than in chickens.
PATHOLOGANATOMICAL CHANGES.
In carnivores:
1. Miliary and nodular tubercles in the lungs and under the pleura (when cut, a thick curdled mass or purulent contents are revealed)
2. Focal or diffuse tubercular tuberculous lymphadenitis and peritonitis.
3. Sharp enlargement of the spleen (8-10 times) with the presence of tubercles
4. Tubercles in the liver, ovaries, uterine wall, kidneys and other areas.
5. Wasting in canines - anemia and sometimes jaundice
In birds:
1. Submiliary and miliary nodules with caseous necrosis in the lymphoid tissue of the iliocercal region of the small intestine
2. Miliary and nodular nodules with caseous necrosis in the liver, spleen, bone marrow
3. Multiple nodes with caseous necrosis in the wall of the small and large intestines with ulceration of the mucous membrane
4. Wasting - atrophy of fat and skeletal muscles, general anemia ( fatty degeneration liver, its rupture, hemorrhage into the abdominal cavity, posthemorrhagic anemia)
DIAGNOSTICS. Clinical and epidemiological data, the results of a pathoanatomical autopsy, an allergic study, and finally - after microbiological research. For this purpose, whole corpses of dead birds or internal organs that have characteristic pathomorphological changes are sent to the laboratory.
Tuberculinization of animals is carried out using purified (PPD) tuberculin for mammals, which is administered:
- for dogs and fur-bearing animals (except minks) in the area of the inner thigh, intradermally in a dose of 0.2 ml;
- for cats in the area of the inner surface of the ear in a dose of 0.2 ml, intradermally;
- minks (foxes and arctic foxes, V.P. Shishkov, V.P. Urban, 1991) intrapalpebrally, in the middle part upper eyelid, in a dose of 0.1 ml (for foxes and arctic foxes - in a dose of 0.2 ml).
In rabbits and nutrias, allergy diagnostics have not found application.
Accounting and assessment of the reaction to tuberculin is carried out in dogs, cats and fur-bearing animals after 48 hours and the animals are recognized as responding when a swelling forms at the site of tuberculin administration.
For birds, dry purified PPD tuberculin, made from avian mycobacteria, is used. It is administered in a dose of 0.1 ml intradermally to chickens in the beard, to turkeys in the submandibular earring, and to geese and ducks in the submandibular fold. The reaction is taken into account after 30-36 hours, where, if sensitization is present, swelling is noted at the injection site.
In the laboratory, the affected organs are cultured on Petragnani or Lowenstein-Jensen medium and a bioassay is performed using rabbits and chickens.
The diagnosis is considered established:
- when isolating a pure culture of the tuberculosis pathogen;
- upon receipt of positive results of the bioassay;
- when characteristic pathomorphological changes are detected in the affected organs during histological examination of the pathological material.
DIFFERENTIAL DIAGNOSTICS. Tuberculosis must be differentiated from actinomycosis and pseudotuberculosis, in birds from leukemia, Marek's disease, pseudotuberculosis, aspergillosis, pullorosis, pasteurellosis.
TREATMENT. Sick rabbits, cats and dogs are killed. WITH therapeutic purpose Before the skins ripen, sick animals are fed tubazide at the rate of 20 mg/kg of body weight, after which the animals are killed. The remaining animals of the disadvantaged group are fed tubazide in a prophylactic dose.
In order to prevent tuberculosis, mink puppies at 20-30 days of age are immunized with the BCG vaccine, which is administered at a dose of 0.2 mg subcutaneously to the inner thigh area.
COMBAT MEASURES. Once a diagnosis is made, quarantine is imposed. In dog breeding kennels, females with offspring are killed, and their skins are used without restriction. Animals from the disadvantaged group are examined for allergies every 60 days until single group negative results are obtained, and after the final veterinary and sanitary measures are taken, quarantine is removed.
In all other categories of fur farms, quarantine is lifted after the slaughter of sick animals, in the absence of changes typical for tuberculosis in the organs and tissues of dead and killed animals during one production cycle (from whelping to slaughter for skins) and the completion of final veterinary and sanitary measures.
Quarantine from an unfavorable rabbit farm is lifted 1 year after the last case of the disease and the completion of final veterinary and sanitary measures.
For disinfection, use the drug DP-2, a 1% solution of glutaraldehyde, an alkaline solution of formaldehyde (containing 3% formaldehyde and 3% sodium hydroxide).
In all reproductive poultry farms, tuberculinization of all adult birds and replacement young animals is carried out once a year.
At poultry farms, at least 10% of the adult poultry population and all replacement young animals from 6 months of age are examined. In an unfavorable point, a bird that reacts to tuberculin is considered sick.
In order to prevent tuberculosis, persons with tuberculosis should not be allowed to serve poultry.
Once a diagnosis is made, quarantine is imposed. Poultry from a dysfunctional poultry house are handed over for slaughter. The export of hatching eggs is prohibited. Received food egg from birds from unfavorable poultry houses is used for baking small-piece bakery and confectionery products.
The import and export of poultry for breeding and consumer purposes is prohibited. To replace poultry from a dysfunctional poultry farm, strictly isolated rearing of chickens hatched from eggs from healthy poultry from prosperous poultry farms is organized.
The droppings are destroyed or disinfected. Disinfection is carried out with an alkaline solution of formaldehyde. They inspect dead birds when they are slaughtered for meat.
The poultry farm is recognized as safe and quarantine is lifted after all the birds are handed over for slaughter and final disinfection is carried out.

Tuberculosis- a chronic infectious disease of many species of agricultural and wild animals, fur-bearing animals and poultry, characterized by the formation in various organs of specific nodules - tubercles, prone to cheesy disintegration.

Historical reference. Tuberculosis has been known since ancient times. Clinical signs of the disease in humans were described by Hippocrates in the 4th century. BC e. The term “tuberculosis” was first used by the French physician Lennec (1819), and the contagiousness of the disease was proven by J. A. Villemin (1865). The causative agent of tuberculosis was discovered by R. Koch (1882), he
produced tuberculin in 1890. Russian researcher X. I. Gelman proposed tuberculin in 1888, but published the work only in 1892. In 1924, Calmette and Guereny prepared the BCG vaccine to prevent tuberculosis in humans.

Animal tuberculosis is registered in many countries around the world. In most European countries it has been practically eliminated.

S. N. Vyshelesssky, P. P. Vishnevsky, M. K. Yuskovets, I. V. Pod-_;.bsky, V. I. Rotov, A. V. Akulov made a great contribution to the study of tuberculosis and the development of health measures , N. A. Naletov et al.

Pathogen. The causative agent of tuberculosis is classified as a microorganism of the genus Mycobacte. There are 3 main types of the causative agent of tuberculosis: 1) M. tuberculosis (human species); 2) M. bovis (bovine species); 3) M. avium (avian). In terms of morphology and cultural characteristics, they are largely similar to each other; These are thin, straight, often slightly curved rods 0.8 - 5.5 µm long, located singly or in groups in smears. Branched, filamentous and coccus-like forms of the microbe are also found. The microbial cell membrane contains fatty wax-like substances, and granularity is noted in the protoplasm.

Mycobacteria are strict aerobes, nonmotile, do not form spores or capsules, acid-resistant; are stained by the Ziehl-Neelsen method in a bright red color, and the microflora are stained in blue.
To grow the causative agent of tuberculosis, glycerin MPA, MPB, potato, egg and synthetic media are used. Cultures grow slowly: mycobacteria of the human species - 20 - 30 days, bovine - 20 - 60 days, avian - 11 - 15 days. If there is no growth, it is recommended to keep the crops in a thermostat for 3 months.

The pathogenicity of individual types of the causative agent of tuberculosis for different species of animals and humans is not the same. Thus, people are most sensitive to the pathogen of the human species; pigs, cats, dogs, cattle, fur-bearing animals are also susceptible, and birds do not get sick (except for parrots). All agricultural and wild animals, fur-bearing animals and humans are sensitive to the bovine pathogen, but birds are not susceptible. Birds and pigs are sensitive to the avian pathogen, and very rarely other mammals and humans become infected with it. Animals infected with avian Lcobacteria may respond to mammalian tuberculin.

The species of the causative agent of tuberculosis is determined by its growth characteristics on artificial nutrient media and by performing a bioassay on chorus pigs, rabbits and chickens.

Sustainable. Mycobacterium geria is very resistant to various environmental factors and chemical substances. This property is explained by the presence of fatty wax substances in the microbial cell.

The causative agent of tuberculosis remains viable in manure for 7 months, dried cow feces - up to a year, in soil - more than two years, river water - up to two months: in meat, frozen and stored in the refrigerator - up to a year, in salted meat - -45- 60 days, in butter - up to 45 days, in cheese - 45-100 days, in milk - up to 10 days. Pasture areas where animals with tuberculosis were grazed remain infected throughout the entire summer period (V.N. Kislenko, 1972).

Heating milk to 70 "C kills the tuberculosis pathogen in 10 minutes, and boiling it in 3 - 5 minutes. The best disinfectants are alkaline 3% -th solution formaldehyde (exposure 1 hour), a suspension of bleach containing 5% active chlorine, a 10% solution of iodine monochloride and a 20% suspension of freshly slaked lime by whitewashing three times with an interval of 1 hour.

In addition to the pathogenic mycobacteria of the three named types of the causative agent of tuberculosis (pathogenic mycobacteria), the genus Mycobacterium contains a large group of atypical mycobacteria. Based on their morphological characteristics, they are difficult to distinguish from the causative agent of tuberculosis; they are often represented by rougher, thicker, non-grained rods of different lengths. Atypical mycobacteria are widespread in nature, and many of them are saprophytes. Once in the body of animals, atypical mycobacteria are able to multiply in it, and create short-term sensitization of the body to tuberculin for mammals.

Epizoogological data. Many species of domestic and wild animals, game animals and birds are susceptible to tuberculosis (more than 55 species of mammals and about 25 species of birds). This disease is most often reported in cattle, pigs, minks and chickens; less often - in goats, dogs, ducks and geese; very rarely - in sheep, horses and cats. Monkeys are highly susceptible to tuberculosis. Among wild ungulates, deer are more often affected. Humans also suffer from tuberculosis.

The source of the infectious agent is animals with tuberculosis, from whose bodies the pathogen is excreted in milk. feces, nasal discharge, sometimes with semen. When cows are infected with any type of tuberculosis pathogen, mycobacteria are always excreted in the milk.

Transmission factors for the causative agent of tuberculosis can be food, water, pastures, and bedding contaminated with secretions of sick animals. manure, etc. Young animals are mainly infected with tuberculosis through milk and skim milk obtained from sick animals. Intrauterine infection of calves is possible. Animals can become infected with the human species through contact with people with tuberculosis.

Animals become infected with tuberculosis mainly through nutrition, but aerogenic infection cannot be ruled out, especially when sick animals are kept together with healthy ones in closed, poorly ventilated, damp rooms. Pigs often get sick when fed raw kitchen waste, as well as from contact with birds with tuberculosis. Birds become infected through nutrition, but transovarial transmission of tuberculosis has also been established in chickens. Birds with tuberculosis lay infected eggs. When infected eggs are incubated, many embryos die, and some of the hatched chickens become a source of the tuberculosis pathogen. Wild birds can be carriers of all three types of tuberculosis pathogen.

Tuberculosis spreads relatively slowly among animals. This is explained by the length of the incubation period of the disease (up to 45 days). Inadequate feeding, unsatisfactory living conditions (overcrowding, dampness) and other unfavorable factors reduce the overall resistance of the animal's body and contribute to the rapid spread of the disease. There is no definite seasonality in the manifestation of the epizootic process in tuberculosis. However, in cattle it is more often recorded during the stall period.

Pathogenesis. The causative agent of tuberculosis, having entered the body through the digestive tract with food or inhaled air, penetrates into the lungs or other organs. At the site of localization of the pathogen, an inflammatory process develops, manifested by cell proliferation and exudation; There is an accumulation of multinucleated giant and pitheloid cells surrounded by a dense layer of lymphoid cells. The exudate accumulated between the cells coagulates, forming a network of zybrin, and an avascular tuberculous nodule is formed - tubercle. It initially has a grayish color and a round shape; its size is from 5 \u200b\u200bthe head of a lentil grain. Soon the nodule is surrounded by a connective tissue capsule. The tissue inside the encapsulated nodule, due to the lack of influx of nutrients and under the influence of the pathogen's -oxins, dies and turns into a dry, crumbly mass resembling wort (caseosis).

If a primary tuberculous nodule develops only at the site of entry of the pathogen (lungs, intestines), then such a fresh, isolated focus is called the primary effect. From there, the pathogen usually travels with the lymph flow to the regional lymph node, where pathological changes also develop. Simultaneous involvement of a regional lymph node is called a complete primary complex. If the process develops only in the regional lymph node, such a process is called an incomplete primary complex.

In a benign course of the disease, the primary focus undergoes calcification, a dense connective tissue capsule forms around it, and further development of the infectious process stops. In an organism with reduced resistance, the process of encapsulation of the pathogen in the primary focus is weakly expressed. Due to insufficient regeneration of connective tissue, the stitches of the tuberculous nodule melt, and mycobacteria enter healthy tissue, which leads to the formation of many small, translucent nodules (biliary tuberculosis). Small tubercles can clump together, forming large tuberculosis foci.

Mycobacteria from tuberculosis foci can enter the blood, which leads to the generalization of the process and the development of tuberculosis foci of different sizes in various organs (liver, spleen, kidneys, etc.). With a long course of the disease, tuberculous foci and cavities can form in the lungs, sometimes reaching the size of varnish. A dense connective tissue capsule grows around them. Tuberculous cavities can communicate with the lumen of the bronchi. In such cases, their contents liquefy and are released when coughing with sputum.

In the generalized form of tuberculosis and extensive lesions of the lungs, gas exchange is disrupted, erythropoiesis is inhibited, anemia is observed, productivity decreases, exhaustion and death of the animal occur.

Course and symptoms. Tuberculosis usually occurs chronically, often without clearly visible signs. A positive reaction to tuberculin in animals occurs on the 14th to 40th day after their infection (incubation period). Most animals with tuberculosis

In appearance and general condition, especially at the beginning of the disease, they are no different from healthy people. Sick animals are identified mainly by allergic and serological testing; tuberculosis lesions are usually detected only during post-mortem examination of organs. As a result of systematic planned studies of livestock (tuberculinization), it is possible to identify the disease in initial stage. The appearance of clinically pronounced forms of tuberculosis indicates a long course of the disease.

In cattle, tuberculosis most often affects the lungs. If they are severely affected, they experience a slight increase in body temperature, a rare but severe cough; with a protracted course of the disease, the cough becomes weak, silent, but painful. Expectoration is almost not observed in livestock; the bronchial mucus released during coughing is swallowed or excreted through the nose. In sick animals, shortness of breath, decreased appetite, fatness and productivity are noted. Visible mucous membranes are anemic. Auscultation of the lungs reveals wheezing, and percussion reveals areas of dullness. Intestinal damage, which is accompanied by diarrhea, is accompanied by rapid exhaustion and increasing weakness of the sick animal.

Damage to the mammary gland is characterized by an enlargement of the suprauterine lymph nodes, which become dense, lumpy, and inactive. In the affected lobes of the udder, compacted painless foci are felt; with significant damage, the configuration of the affected lobe changes. When milking, watery milk with an admixture of blood or curdled mass is released. When the genital organs are affected, increased sexual heat and barrenness are noted in cows, and orchitis in bulls.

Porcine tuberculosis is asymptomatic. Sometimes an increase in the submandibular and retropharyngeal lymph nodes is observed. Abscesses may appear in the affected nodes, after opening which a purulent-curdled mass is released. With extensive lung damage, coughing, vomiting, and difficulty breathing occur.

Sheep and goats suffer from tuberculosis rarely and asymptomatically. With a highly expressed process, the clinical signs are similar to those. cattle.

Tuberculosis in birds is chronic, with unclear clinical signs. The generalized form is accompanied by lethargy, decreased egg production, and exhaustion (atrophy of the pectoral muscles). When the intestines are damaged, diarrhea is observed; liver - icteric staining of the mucous membranes and skin. Sometimes lameness and the formation of tumor-like formations on the plantar surface of the extremities are noted.

Among fur-bearing animals (foxes, mink, nutria), tuberculosis jaiue affects young animals. Patients experience weakness and progressive exhaustion; in the pulmonary form, cough and shortness of breath.

Damage to the intestines is accompanied by diarrhea, and the liver is accompanied by icteric staining of the mucous membranes. Foxes sometimes develop ulcers on their skin that take a long time to heal.

Pathological changes. Characteristic of tuberculosis is the presence in various organs and tissues of the animal of specific nodules (tubercles) the size of a millet grain to a chicken egg or more.

Tuberculous foci are surrounded by a connective tissue capsule, their contents resemble a dry, crumbly, curdled mass (caseous necrosis). With prolonged illness, tuberculous nodules can become calcified.

In ruminants, tuberculous lesions are more often found in the lungs and lymph nodes of the chest cavity. In the lungs, dense, brownish-grayish foci are found; on a section they are shiny, greasy (no necrosis), often with caseosis in the center; sometimes the lesions have purulent foci. Occasionally, cavities of various sizes are found in animals and goats). Lymph nodes are more often affected. They are enlarged, dense, lumpy, with caseous tissue disintegration in the center of the node.

When the serous integument is affected, the same (pearly mussel) dense, shiny tuberculous nodules, reaching the size of a hazelnut, are found on the pleura and peritoneum. The intestinal form of tuberculosis is prolonged by round ulcers with roller-shaped edges on the mucous membrane of the jejunum and ileum.

Diagnosis of tuberculosis made on the basis of an analysis of epizootic data, clinical signs and the results of allergic, serological (RSC with tuberculosis antigen), pathological, histological, bacteriological biological studies.

The clinical method of diagnosing tuberculosis is of limited importance, since the clinical signs of the disease in animals are not typical enough, and at the onset of the disease they are not present at all. The main method of intravital diagnosis of tuberculosis is an allergic study. Animals are subjected to tuberculinization from 2 months of age. For the study, tuberculin (allergen) is used - sterile filtrate of killed cultures of the causative agent of tuberculosis. In the USSR, 3 varieties of tuberculin are prepared: alttuberculin, dry purified tuberculin (PPD) for mammals and dry purified tuberculin (PPD) for birds.

Altuberculin is prepared from the filtrate of a killed broth culture of the causative agent of bovine tuberculosis. It is used for allergic diagnosis of tuberculosis in all mammals except pigs and monkeys.

Dry purified tuberculin (PPD) for mammals (protein purified derivative) consists of freeze-dried precipitated proteins of the cultural filtrate of the causative agent of bovine tuberculosis, grown on a synthetic nutrient medium. It is used for allergic diagnosis of tuberculosis in all mammals.

Tuberculinization methods. In the USSR, two methods are used: intradermal - the main method of allergic diagnosis of tuberculosis in all species of mammals, animals and birds (except horses) and ocular (ophthalmic test) - used to diagnose tuberculosis in horses. In some cases, this test is used in cattle simultaneously with intradermal testing.

Place of injection. With the intradermal method, tuberculin is administered to: cattle, buffalos, zebu, deer (deer) - in the middle third of the neck; For breeding bulls, tuberculin is allowed to be injected into the skin of the subcaudal fold, for pigs - in the area of the outer surface of the auricle at a distance of two centimeters from its base (on one side of the auricle, PPD-tuberculin for mammals is injected, on the other - PPD for birds). For pigs aged 2 - 6 months, it is better to inject tuberculin into the skin of the lumbar region, moving 5 - 8 cm away from the spine (tuberculin for mammals is injected on one side, for birds on the other), using a needleless injector of the IBV-01 brand. . For goats, sheep, dogs, monkeys, fur-bearing animals (except minks), tuberculin is injected into the area of the inner thigh; minkam - intrapalpebrally into the upper eyelid; for camels - into the skin of the abdominal wall in the groin area at the level of the ischial tuberosity; for chickens - in the beard, for turkeys - in the submandibular earring; geese, ducks - in the submandibular fold, pheasants, peacocks, parrots, pigeons, cranes, herons, storks, flamingos - in the area of the outer surface of the lower leg, 1-2 cm above the ankle joint. The fur at the site of tuberculin injection is cut (feathers are plucked), the skin is treated with 70% alcohol.

For tuberculinization, special needles for intradermal injections with a double tube (MRTU No. 46-84-62) or needles No. 0612 and syringes with a slider with a capacity of 1 - 2 ml are used. Needleless injectors are widely used to administer tuberculin to animals.

During intradermal tuberculinization, tuberculin is administered once in a volume of 0.2 ml to all mammals, except monkeys, minks and birds (they are given a dose of 0.1 ml).

Recording and assessment of the reaction in cattle, buffaloes, zebu, camels and deer is carried out 72 hours after administration of the drug, in goats, sheep, pigs, dogs, monkeys, fur-bearing animals - after 48 hours; in birds - after 30 - 36 hours. The local reaction to the introduction of tuberculin can be assessed as positive or negative.

The reaction is considered positive if a diffuse (without clear boundaries with the surrounding tissue), doughy consistency, painful inflammatory swelling is formed at the site of tuberculin injection, accompanied by hyperemia and an increase in local temperature. In some animals, the reaction manifests itself in the form of a dense, painless, clearly contoured swelling. Cattle, buffalo, zebu, camels and deer are considered responsive to tuberculin if the above changes are present at the site of tuberculin injection and a thickening of the skin fold (compared to the thickness of the fold of unchanged skin near the site of tuberculin injection) of 3 mm or more.

Sire bulls tuberculinized in the subcaudal fold are considered to react when an inflammatory swelling forms at the site of tuberculin injection and the skin fold thickens by 2 mm or more.

Intradermal tuberculin test is a highly specific reaction to tuberculosis. However, it depends on the general immunoreactivity of the body and the sensitivity of animals to tuberculin. In animals of low fatness, old, deep-pregnant animals, as well as with a generalized tuberculosis process, the reaction to tuberculin may be weakly expressed or not manifested (anergy) It should also take into account that nonspecific (paraallergic) reactions to tuberculin for mammals are sometimes possible due to sensitization of the body by avian mycobacteria, the causative agent of paratuberculosis and atypical mycobacteria, as well as other reasons. However, non-allergic reactions are unstable and disappear after a few months

Differentiation of specific reactions from nonspecific ones, if necessary, is carried out by a simultaneous test with avian tuberculin or a complex allergen from atypical mycobacteria (AM) and laboratory tests

Tuberculinization by the eye method is carried out twice with an interval of 5-6 days. Tuberculin is applied with an eye pipette to the conjunctiva of the lower eyelid and applied to the cornea of the eye (with the lower eyelid retracted) in the amount of 3-5 drops. The reaction to tuberculin is taken into account after the first administration of tuberculin after 6, 9, 12 and 14 hours, after the second injection of tuberculin - after 3, 6, 9 and 12 hours The reaction is considered positive if mucous or purulent secretion occurs from the inner corner of the eye, accompanied by hyperemia and swelling of the conjunctiva. The diagnosis of tuberculosis is considered established, and a farm is declared unfavorable if, during the diagnostic slaughter of 2-3 heads of animals that react positively to tuberculin, pathological changes in organs or lymph nodes characteristic of this disease are found, and in the absence of typical changes for tuberculosis - according to positive results of bacteriological, histological and biological studies

Treatment . Animals with tuberculosis are not treated; they must be slaughtered. In dysfunctional fur farms, tubazid (isoniazid) is used to prevent tuberculosis in minks. The drug is given with food in a dose of 0 mg/kg of animal weight, once a day for 75 days.

Immunity in tuberculosis non-sterile, persisting as long as the mycobacteria are in the body. Phagocytosis is incomplete and phagocytosed mycobacteria do not die. The body produces agglutinins and complement-fixing antibodies, but their role in immunity is insignificant. Protection is mainly determined by the body’s ability to stop the pathological process and limit the pathogen in granulomas-tubercules. For specific prevention For mink tuberculosis, the dry BCG vaccine used in medicine is used. It is used to vaccinate clinically healthy mink puppies at the age of 20-30 days in farms affected by tuberculosis. Immunity in vaccinated minks lasts 6 - 8 months.

Prevention and control measures. Measures to combat tuberculosis include the protection of healthy farms from the introduction of the infectious agent from the outside, systematic research in order to timely identify sick animals, the improvement of farms unfavorable for tuberculosis by slaughtering sick animals, isolated rearing of healthy young animals and carrying out a complex of veterinary, sanitary, organizational and economic measures aimed at protecting healthy livestock and destroying the tuberculosis pathogen in the external environment; protecting people from tuberculosis infection.

In prosperous farms, all measures should be aimed at protecting the farm from the introduction of the disease pathogen. For this purpose, farms are stocked with healthy animals from farms that are free from tuberculosis. Newly received animals are examined for tuberculosis during a 30-day quarantine period. Feed is purchased only from farms that are free from tuberculosis. The skim milk supplied to the young animals is pasteurized, and the collected lichen waste is subjected to heat treatment. Persons with tuberculosis are not allowed to serve animals and keep poultry on the territory of livestock farms. Periodically, preventive disinfection of livestock premises is carried out, rodents and ticks are destroyed, and measures are taken to improve the feeding and maintenance of animals. In breeding farms it is strictly prohibited to use peat for animal feed and bedding.

In order to timely identify animals with tuberculosis and monitor the welfare of farms with regard to this disease, routine diagnostic tests of animals for tuberculosis are carried out annually. Cows, heifers and young cattle from 2 months of age, stud bulls, sows, boars, camels intended for sale for breeding purposes are examined.

Twice a year, cattle from breeding farms and farms supplying animals for stocking livestock complexes, milk and dairy products directly to children's and medical institutions, rest homes or to retail chains, as well as farms territorially bordering on disadvantaged areas, are tested for tuberculosis. tuberculosis points. Cattle belonging to citizens living on the territory of these farms are examined once a year.

If tuberculosis occurs, the farm (farm) is declared unfavorable, restrictions are imposed, and a calendar plan of measures to eliminate the disease is drawn up.

In farms affected by tuberculosis in cattle, buffaloes and reacting animals, they are immediately isolated and slaughtered within 15 days. Young animals born from sick animals are fattened in isolated conditions and sent for slaughter. The remaining animals (not responding to tuberculin) of the unfavorable farm are examined for tuberculosis every 30 - 45 days until two negative results are obtained in a row for the group, after which two more control studies are carried out with an interval of 3 months. If negative results are obtained and there are no other indications for tuberculosis, this group of animals is considered healthy.

Calves that react positively to tuberculin are isolated and after fattening they are slaughtered. Non-responders are examined 2 more times with an interval of 30-45 days, then after 3 months. If a negative result is obtained for the entire group, they are considered healthy and used for production purposes only within the farm.

Milk obtained from animals with clinical signs of tuberculosis is fed to fattening cattle after boiling for 10 minutes, and from animals that react positively to tuberculin, milk after boiling is used within the farm or sent for processing into ghee. Milk from animals in the recovery group (before putting them under control) is neutralized in continuous pasteurizers at a temperature of 90 °C for 5 minutes, or at a temperature of 85 °C for 30 minutes. In the absence of pasteurizers, milk is boiled.

In poultry farms, all birds with tuberculosis and weak birds are slaughtered immediately, and the rest of the birds are slaughtered after the end of the laying and fattening season. Eggs obtained from birds in a dysfunctional poultry house are used in baking bakery products.

In pig farms unaffected by tuberculosis, all pigs reacting to tuberculin are immediately isolated and slaughtered immediately or after fattening. The remaining pigs from 2 months of age are examined every 30-45 days for tuberculosis until two consecutive negative results are obtained for the group, after which this group of pigs is declared healthy.

Horses that react to tuberculin are isolated and retested after 45 to 50 days. If the reaction is maintained, they are submitted for battle, and the rest of the livestock is examined every 45 - 60 days until a single negative result is obtained, after which they are declared healthy.

Sheep and goats at positive reaction are handed over for slaughter, and the remaining animals are examined after 45 - 60 days until a negative result is obtained for the entire group (flock).

Definition of disease

Tuberculosis is a chronic infectious disease of most species of animals and humans, characterized by progressive emaciation and the formation in organs and tissues of specific nodules - tubercles, prone to cheesy necrosis and calcification. Historical background. The disease has been known since ancient times. Hippocrates in the 4th century. BC e. described the clinical signs of tuberculosis in humans. The name of the disease “tuberculosis” was introduced by K. Lenek (1819). The contagious nature of the disease was proven by J. A. Villemin in 1865. The causative agent of tuberculosis was discovered by R. Koch in 1882, and in 1890 he developed a method for producing tuberculin. Bacteriologist A. Calmette and veterinarian S. Guerin in 1924 produced the BCG vaccine (BCG - Bacillus Calmette - Guerin) for the specific prevention of tuberculosis in humans. Tuberculin was first proposed for the diagnosis of tuberculosis in animals by R. G. Gutman in 1891.

Spread of the disease

Tuberculosis is common in many countries of the world. In developed countries of Europe and North America, the disease has been virtually eliminated. There is no tuberculosis in the Republic of Belarus widespread(1-3 unfavorable points for tuberculosis in cattle are registered annually). However, the problem of tuberculosis remains relevant to this day.

Economic damage

The disease causes great economic damage, which, when tuberculosis occurs, consists of the costs of carrying out quarantine or restrictive measures, and slaughtering productive animals that react to tuberculin. Large costs are also associated with carrying out preventive measures, including annual allergic tests of animals in tuberculosis-free farms. The social significance of tuberculosis is enormous. Every year, about 10 million people worldwide fall ill, of whom 3.5 million die from this disease. The epidemiological situation regarding tuberculosis is difficult in the Republic of Belarus. In this regard, it is believed that tuberculosis is more a medical problem than a veterinary one, and the disease itself is classified as an anthropozoonosis. An entire branch of medicine deals with this disease - phthisiology (from the gr. phthisis - exhaustion, consumption).

Etiology

The causative agent of tuberculosis belongs to the genus Mycobacterium, which includes both pathogenic and non-pathogenic (atypical) species of mycobacteria. Tuberculosis in mammals is caused by M. tuberculosis (human species), M. bovis (bovine species), and in birds - M. avium (avian species). M. bovis causes tuberculosis in cattle, pigs, mink, deer and humans. M. tuberculosis is pathogenic for humans and pigs, and can infect cattle, but the disease in this case proceeds latently, usually without visible changes in the body. M. avium causes disease in birds and can cause tuberculosis-like lymphadenitis in pigs. M. murium causes disease in mice, M poikilotermorum - in cold-blooded animals, M. paratuberculosis - paratuberculosis in cattle. Non-pathogenic mycobacteria are widespread in nature; when they enter an animal’s body, they cause sensitization, which manifests itself in the form of paraallergic reactions to tuberculin. Morphologically, the causative agents of tuberculosis are rods 0.6 microns in width and 1-6 microns in length, immobile, do not form spores or capsules, aerobes have a well-developed cell wall. This is the basis of the Ziehl-Neelsen differential staining method, as a result of which mycobacteria are stained ruby red, and all other microorganisms are blue.

Tuberculosis pathogens grow slowly when cultured from pathological material. Colonies of bovine Mycobacterium tuberculosis appear only after 20-60 days, and avian ones - 15-30 days after sowing. It is recommended to keep the crops in a thermostat in the absence of mycobacterial growth for at least three months. To isolate tuberculosis pathogens, complex solid nutrient media are used: Levenshtein-Jensen, Gelberg, Petragnani, FLST-Zl, VKGidr. The causative agent of human tuberculosis forms polymorphic colonies, often having a cream color, but in most cases it cannot be distinguished from M. bovis by the appearance of the colonies. M. avium grows in the form of smooth, shiny, often turban-like colonies that emulsify well in aqueous solutions (S-form colonies). The species of mycobacteria is determined by biochemical properties and the degree of pathogenicity for laboratory animals. The pathogenicity of mycobacteria for laboratory animals is determined by subcutaneous or intravenous administration of 1 mg (wet weight) of the bacterial mass of a 3-4-week culture to three rabbits, three guinea pigs and three chickens.

Under the influence unfavorable factors(antibiotics, lysozyme, etc.) the causative agent of tuberculosis may lose the ability to synthesize the peptidoglycan backbone of the cell wall, resulting in the formation of L-forms (transformed mycobacteria) with low virulence and capable of surviving in unfavorable conditions. L-forms of mycobacteria can persist for a long time in animals and humans. Transformed mycobacteria in some cases are capable of reverting to the classical forms of the pathogen, causing a relapse of the disease; to identify them, a special Shkolnikova medium, VKG medium with a growth stimulator, is used. The presence of waxy substances in the shell of mycobacteria determines the high stability of mycobacteria in the external environment. Mycobacteria persist in soil for up to 5 years; in manure, litter - up to 1.5 years; in water - up to 10 months, in feces, on pastures, frozen meat - up to a year; in butter, cheeses - up to 10 months. In milk, when heated to +85 °C, the pathogen dies after 30 minutes, and when boiled, after 5 minutes. Pasteurization of milk from cows reacting to tuberculin is carried out at +90 °C for 5 minutes, at +85 °C for 30 minutes. The most effective disinfectants are a 3% alkaline solution of formaldehyde and 5% solutions of chlorine-containing drugs. It is recommended to use Vitan, KDP (combined surface disinfectant), Belstril, Glutex and other agents for tuberculosis.

Epizootological data

More than 55 species of mammals and about 25 species of birds are susceptible to tuberculosis. Most often, cattle, pigs, and poultry - chickens suffer from tuberculosis. Goats, dogs, ducks and geese get sick less often. Sheep, horses and cats are very rarely affected by tuberculosis. Of the wild animals, deer are the most likely to get sick. Susceptibility to tuberculosis depends on the level immune status animal and the degree of negative impact of various stress factors on its body (hypothermia, low level of feeding, microclimate disturbance, etc.). A higher susceptibility to tuberculosis has been established in highly productive animals and black-and-white breeds of cattle. Relative resistance to tuberculosis has been established in beef breeds of cattle. The issue of sensitivity is important different types animals and humans to various types of mycobacteria. Animals infected with avian Mycobacterium tuberculosis may respond to mammalian tuberculin. People can become infected with all types of mycobacterium tuberculosis, but more commonly human and less commonly bovine.

When people are infected with avian mycobacteria, they are sometimes observed acute onset diseases. Tuberculosis in dogs and cats can be caused by all three types of mycobacteria. The source of the infectious agent is animals with tuberculosis, and less often humans. Mycobacteria are excreted from the body in sputum, exhaled air, feces, milk, and rarely in urine and semen. The intensity of the division of the pathogen with various secretions and excreta depends on the location and nature of the tuberculosis process. Transmission factors include air, feed, water, bedding, manure and other objects contaminated with the pathogen. Infection of animals occurs through nutritional and aerogenic routes. The disease spreads slowly among animals, with massive re-infection occurring within 1-2 years. Epizootic situation regarding tuberculosis in the Republic of Belarus in the present time is characterized by the presence of single disadvantaged points per year. A peculiarity of the epizootic situation regarding tuberculosis and the republic is that the bulk of reacting animals are identified in farms that are free from tuberculosis. Tuberculosis in animals occurs in the form of enzootics, the infection rate of animals can reach 40-80%, sick animals die in rare cases.

Pathogenesis

In a resistant organism, having penetrated the lungs or other organs, mycobacteria multiply and cause tissue irritation and inflammation. At the site of the future tubercle, leukocytes appear around tuberculous mycobacteria. They phagocytose and partially destroy microbes, but at the same time die themselves. Subsequently, cells such as monocytes and histiocytes multiply in this area, which begin to absorb mycobacteria and, in turn, become necrotic, but along the periphery of the inflammatory focus these cells differentiate into lymphoid, epithelioid and giant. In a typical tubercle in the center there is a necrotic area in the form of a structureless oxyphilic mass with fragments of nuclei and often with particles of lime. This area is limited by granulation tissue, consisting of two zones: the inner zone of epithelioid and individual giant cells and the outer zone of lymphoid cells. Exudate is deposited between the cells and fibrin coagulates.

An avascular tuberculous nodule is formed, which is subsequently encapsulated. Due to lack of nutrient supply and exposure to bacterial toxins tissue cells in the tubercle they die and a curdled mass is formed, impregnated with lime salts. Tuberculosis bacteria in such a nodule can die, and sometimes persist for a long time. In this case, the disease does not manifest itself clinically, and the animal appears healthy in appearance. If the body's resistance is reduced, the capsule is not formed or is not strong enough, the pathogen from the primary focus penetrates into the surrounding tissues, where new nodules form. They merge with each other, forming large tuberculous foci. The pathogen can enter the blood, which leads to a generalization of the process with the development of tubercles in various organs and tissues. In cattle, the serous membranes may be affected with the formation of dense shiny growths (pearly mussel). In the generalized form of tuberculosis in sick animals, gas exchange is disrupted, anemia develops, hematopoietic processes are inhibited, and exhaustion and death of the animal occur.

Course and symptoms of the disease

Clinically, tuberculosis in animals is currently practically not manifested, since infectious process with tuberculosis it develops slowly, and thanks to regular scheduled allergy tests, sick animals are identified for early stages diseases when clinical signs do not have time to develop. The duration of the incubation period for tuberculosis is 2-6 weeks. The course of the disease is chronic or latent. There are generalized, pulmonary, intestinal and genital forms of the disease. There may be damage to the udder, genitals and serous membranes (pearl oyster). With the pulmonary form, cattle experience a rare but painful cough, shortness of breath, decreased appetite, decreased productivity and body condition. Damage to the udder is characterized by an increase in the supra-udder lymph nodes, and in the udder parenchyma - the formation of dense, painless foci. Milk is watery and contains blood or a curdled mass. The genital form is manifested by increased sexual heat, barrenness, and in bulls - orchitis. In the generalized form of tuberculosis, the superficial lymph nodes are enlarged, lumpy, and inactive. In pigs the disease is asymptomatic. An increase in the submandibular and retropharyngeal lymph nodes may be observed. Tuberculosis in small cattle is predominantly asymptomatic.

Pathological changes

Characteristic of tuberculosis is the formation in various organs and tissues of a sick animal of specific nodules (tubercules) the size of a millet grain to a chicken egg or more. They can form in almost all organs and tissues, except horny ones. However, in cattle the following are most often affected: lymph nodes of the chest cavity - in 100%, lungs - in 99%, liver - in 8%, spleen - in 5%, udder - in 3%, intestines - in 1% of cases.

In the lungs, tubercles are most often found along the blunt edge of the diaphragmatic lobe. The tubercles are dense, grayish or grayish-yellow in color with a cheesy mass in the center (caseous necrosis), partially or completely calcified, surrounded by a connective tissue capsule. The liver, kidneys, spleen and mammary gland are affected in the generalized tuberculosis process. Tuberculous changes in the serous integument of the thoracic and abdominal cavities (pearly mussel) are also recorded in generalized tuberculosis in cattle. No pathological changes are found in cattle sick with tuberculosis if they are infected with mycobacteria of human and avian species. In pigs, tuberculous lesions are most often found in the lymph nodes of the mesentery and head, less often in other organs. In horses, tuberculous changes are more often found in the lymph nodes of the mesentery of the head, mediastinal and less often in other lymph nodes.

Diagnostics

It should be carried out comprehensively, taking into account epizootological data, clinical signs, results of allergic studies, pathological autopsy and laboratory tests. Epizootiological and clinical methods diagnostics are poorly informative. The pathoanatomical method in cattle (only in this type of animal) provides grounds for making a final diagnosis of tuberculosis (by commission), when pathological changes in organs and tissues typical for tuberculosis are detected. The diagnosis of tuberculosis based on the pathological method cannot be established in other animal species due to the atypicality of their pathological changes. The main method of intravital diagnosis of tuberculosis is allergic, for which the following tuberculins are used:

PPD tuberculin for mammals, which is produced in two types: in the form of a standard solution and dry tuberculin. In the form of a standard PPD solution, tuberculin for mammals is a sterile filtrate of a culture of the causative agent of bovine tuberculosis and its waste products grown on a synthetic Soton nutrient medium. Dry PPD tuberculin for mammals is a sterile filtrate of a culture of the causative agent of bovine tuberculosis and its waste products, grown on a synthetic Soton nutrient medium and subjected to lyophilic drying. There are: intradermal, palpebral (in the thickness of the eyelid) and ocular tuberculin tests. When carrying out intradermal tuberculinization, animals are examined for tuberculosis starting from two months of age. Cows are examined regardless of the period of pregnancy. Females of other animal species - 1-2 weeks after birth. Animals are not allowed to be examined within 3 weeks after vaccination against infectious diseases. Before the introduction of tuberculin, the hair of the animals is cut off, the skin is treated with 70% ethyl alcohol - 1 ml per treatment.

Tuberculin is administered intradermally, in a dose of 0.2 ml, to a large cattle-in in the middle of the neck, at the intersection of the longitudinal and transverse lines, to the bulls in the sub-caudal fold. For pigs - injected in the area of the outer surface of the ear, 2-3 cm from its base, while tuberculin for mammals is injected into the skin of one ear, and tuberculin for birds is injected into the skin of the other ear. For pigs aged 2-3 months, it is better to inject tuberculin with a needle-free injector into the skin of the lumbar region, left and right, 5-8 cm from the spine. In goats and sheep, tuberculin is administered palpebrally (into the thickness of the lower eyelid), departing from the edge by 1.5-2 cm (in a dose of 0.2 ml). Accounting for the results of tuberculinization: in cattle - after 72 hours; in pigs, sheep and goats - after 48 hours. In cattle, the site of tuberculin injection is palpated. When a swelling is detected, regardless of its nature, its thickening is determined by comparing it with the thickness of the fold of unchanged skin near the site of tuberculin injection. Thickening of the skin fold is measured with a cutimeter. In sheep and goats, when reading the palpebral tuberculin test, the eyelids of the left and right eyes are compared. In other animal species (pigs, etc.), the site of tuberculin injection is palpated and inspected. Based on the results of recording the reaction, animals are divided into:

responsive to tuberculin;

not responding to tuberculin.

The following are considered responsive: cattle (except bulls) - when the skin fold thickens by 3 mm or more, regardless of the nature of the swelling (swelling, pain, increased local temperature). In bulls (oxen), goats, sheep, pigs - when a noticeable swelling forms at the site of tuberculin injection. In farms that are unfavorable for tuberculosis in cattle, including those belonging to the public, it is allowed to use a double tuberculin test for a more complete identification of sick animals. In these cases, for animals that do not respond to the first injection of tuberculin, the drug is administered to the same place and in the same dose after 72 hours, i.e., when the reaction is read. The response to repeated administration of tuberculin is taken into account after 24 hours and assessed as above. The ocular tuberculin test is used to diagnose tuberculosis in horses. In cattle, it is used only simultaneously with intradermal testing in farms unaffected by tuberculosis for additional identification of infected animals. The ocular tuberculin test is carried out twice with an interval of 5-6 days between the first and second administration of tuberculin. Tuberculin in an amount of 3-5 drops is applied with a pipette to the conjunctiva with the lower eyelid retracted.

Recording and evaluation of the reaction is carried out 3, 6, 9 and 12 hours after repeated administration of tuberculin. In animals reacting to tuberculin, the following is noted: hyperemia and possible swelling of the conjunctiva, accumulation of purulent and mucopurulent secretion in the conjunctival sac and its flow out from the inner corner of the eye in the form of a cord. In the republic, an intravenous allergy test is not used to diagnose tuberculosis due to the possible sensitization of the animal body after its use. When responsive animals are identified in a tuberculosis-free farm, a simultaneous test with KAM or PPD-tuberculin for birds is carried out to differentiate paraallergic reactions to tuberculin. PPD-tuberculin for mammals and CAM are injected intradermally into symmetrical areas of the neck from different sides. When taking into account the reaction after 72 hours, the intensity of the reactions is compared. A reaction only to tuberculin for mammals or a more intense one to this drug is assessed as “+”. A reaction with the same thickening of the skin fold is assessed as “=”, and with a more pronounced reaction to an allergen from non-tuberculous mycobacteria as “-”.

Statistical processing of the results is carried out in accordance with the current instructions. When cattle are infected with atypical mycobacteria, the number of animals reacting with a score of “-” is 2-6 times more number animals with a rating of "+" and "=". A significant number of animals with a sample score of “+” and “=" indicate the likelihood of infection with the causative agent of tuberculosis of bovine or human species, and therefore such animals must be submitted for diagnostic slaughter. The reliability of the simultaneous test is 77-100%. If, during routine allergy studies in tuberculosis-free farms, animals that react to tuberculin are identified, then the animals with the most pronounced reactions (5-10 animals) are subjected to diagnostic slaughter. In the absence of characteristic pathological changes, material is taken from the killed animals for bacteriological examination. For bacteriological examination, lymph nodes from mammals are sent to the laboratory: retropharyngeal, submandibular, bronchial, mediastinal, portal, mesenteric, taken in the area of the ileocecal junction and ileum; pieces of organs with changes suspicious for tuberculosis. Paired lymph nodes are cut out from both sides of the carcass, indicating their name on the label, which is packaged with the sample. Carcasses (corpses) of birds and small animals are sent to the laboratory as a whole for research.

Samples of pathological material selected for bacteriological examination are delivered to the laboratory fresh or frozen. Preservation of samples with a 30% sterile aqueous solution of chemically pure glycerin is allowed. The laboratory conducts bacteriological examination of the material, including microscopy, isolation of pure culture and infection of laboratory animals. For microscopic examination 2 smears are prepared from each organ and lymph node and stained with Ziehl-Neelsen. For fluorescence microscopy, smears are stained with a mixture of fluorochromes. Pathological material for cultural and biological studies is processed by the Gone-Levenshtein-Sumiyoshi method or the Alikaeva method. For the cultivation of Mycobacterium tuberculosis, solid egg, Levenstein-Jensen, Gelberg and Petragnani nutrient media are used. Biological research (bioassay) is used to detect the causative agent of a disease in the material under study and determine its species. Guinea pigs, rabbits and chickens are used for bioassays. The diagnosis of tuberculosis is considered definitively established in one of the following cases:

when changes typical of tuberculosis are detected in organs and tissues (only in cattle);

when isolating a culture of the causative agent of tuberculosis of bovine or human species;

upon receipt of positive results from a biological test.

In addition, methods for diagnosing tuberculosis using ELISA and PCR have been developed, allowing for intravital diagnosis of the disease by examining blood or bronchial mucus, as well as using the VKG medium with subsequent differentiation of mycobacteria grown on it.

Differential diagnosis

Small tuberculous nodules should be distinguished from granulomas of parasitic, mycotic and other origin. Mycotic granulomas are macroscopically difficult to distinguish from tuberculous granulomas. Actinomycomas and nodules of parasitic origin contain a necrotic mass and are easily squeezed out. The inner surface of the capsule of such nodules is shiny and smooth.