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Avian influenza: an overview of the disease from A to Z. Avian influenza virus - symptoms, modes of transmission, treatment and how dangerous it is for humans

Bird flu is an infectious disease of birds that is caused by 15 varieties of influenza virus. In 1997, it was found that one type of avian influenza virus contributes to the disease not only in birds, but also in humans, leading to damage to the respiratory tract.

Such overcoming of the barrier between species was made possible due to numerous mutations of the virus.

Causes of bird flu

The disease is caused by influenza A virus subtype H5N1. On the surface of the virus there are antigen proteins - hemagglutinin (H) and neuraminidase (N), which act as “spikes”. Due to hemagglutinin, the virus “sticks” to the cells of the mucous membrane, and with the help of neuraminidase, it penetrates into the cells and, after multiplying, comes out back into them. Different combinations of H and N proteins determine influenza virus subtypes.

The source of infection for avian influenza is wild waterfowl (wild ducks and geese), which themselves do not get sick. Stopping in ponds with stagnant water, they introduce a virus with feces that can live up to 400 days at optimal temperatures - from +10-12° to +30°C. The virus is transmitted through water to waterfowl, and from it to other domestic birds. Turkeys, chickens and ducks are most susceptible to infection.

Humans can become infected with avian influenza through respiratory droplets by inhaling droplets of mucus or saliva produced by sick poultry when they cough or sneeze. Contact transmission of the virus is also possible by touching objects that contain saliva from a sick bird or bird droppings.

The avian influenza virus can survive for many years at temperatures below minus 70°C. Consequently, the risk of virus persistence in chilled and frozen poultry meat increases. But there cannot be a virus in fried or boiled chicken meat, since it dies already at 70°C. The virus cannot withstand repeated (more than five times) freezing and thawing. But if you eat raw eggs from a sick bird, there is a risk of contracting bird flu.

The risk of getting avian flu is higher among poultry farm workers, rural residents who keep poultry, as well as children, pregnant women and the elderly.

Symptoms of bird flu
The incubation period for bird flu ranges from several hours to five days. This is the time that passes from the moment of infection to the appearance of symptoms of the disease.

Symptoms of avian influenza are similar to those of severe regular influenza in humans. Body temperature rises to 38-40 degrees, chills, severe headache, pain in muscles and joints occur. This is accompanied by severe weakness, loss of appetite, sore throat, cough, and runny nose. Conjunctivitis may develop - redness of the eyes, a feeling of sand in the eyes, watery eyes. In some cases, loose, watery stools (diarrhea) and repeated vomiting appear.

Why is it dangerous?
Complications of avian influenza include severe pneumonia and acute respiratory distress syndrome, which can lead to severe respiratory failure and death of the patient. It is also possible to develop sinusitis, bronchitis, otitis, myocarditis, pericarditis and renal failure. Complications from the lungs, kidneys and heart can lead to death in 50% of patients with avian influenza.

Diagnosis of bird flu
Diagnosis of bird flu is carried out by a general practitioner and an infectious disease specialist.

To confirm the diagnosis of avian influenza, a blood test is performed for antibodies to the influenza virus, polymerase chain reaction (PCR) of discharge from the nose and throat, as well as rapid tests.

Treatment of bird flu
A person sick with bird flu is urgently hospitalized in a hospital and placed in a separate room (isolated from others).

A patient with bird flu must remain on strict bed rest. Antiviral drugs (neurominidase inhibitors), antipyretics, drugs to facilitate breathing through the nose (vasoconstrictor drops or sprays), antitussives (expectorants, mucolytics) are prescribed.
If complications develop, the patient may need artificial ventilation (ALV) or hemodialysis (in case of severe kidney damage).

Nota Bene!
The bird flu virus is not transmitted from person to person. Scientists fear that if this becomes possible as a result of virus mutations, a pandemic will arise, the outcome of which is difficult to predict.

Interesting Facts

Avian influenza was first described in 1878 by the Italian veterinarian Eduardo Perroncito. He called the disease chicken typhus. In birds sick with influenza, the number of eggs laid decreases, breathing problems may occur, and a lack of coordination of movements is detected - head rotation, neck curvature, lack of response to stimuli, and a depressed state. If the flu occurs at lightning speed, the birds quickly die before symptoms of the disease appear.
The first cases of human infection with avian influenza virus were recorded in Hong Kong in 1997 during an outbreak of influenza in poultry. At that time, 18 people fell ill, and 6 of them died. Researchers have found that the culprit of the disease was the H5N1 virus. It was then established that the virus is transmitted from birds to humans.
From February 2003 to September 2009, according to the World Health Organization, in 16 countries around the world, 442 people were confirmed infected with the avian influenza virus, half of them died. The last fatality from bird flu was in January 2009 in China.

Prevention of bird flu
To prevent the spread of avian influenza, healthy poultry are vaccinated against the disease and those that become ill are destroyed.

To prevent avian influenza, the World Health Organization (WHO) recommends:

do not touch wild birds or sick poultry;
do not touch or use dead or sick birds for cooking;
do not eat raw or undercooked poultry meat and eggs;
poultry meat and eggs must be stored in the refrigerator separately from other products;
if a sick bird is discovered, you must inform the veterinary service;
If flu-like symptoms appear after contact with a bird, you should consult a doctor as soon as possible.

Expert: Khromova G.V., Candidate of Medical Sciences, infectious disease specialist

Prepared based on materials:

Shuvalova E. P. Infectious diseases. - M.: Medicine, 2005.

Bird flu (H5N1) is a type of influenza virus that affects birds and can be transmitted from them to humans. Transmission of the disease occurs mainly through the fecal-oral route.

Historical reference

Avian influenza was first described in Italy in 1880. At the beginning of the 21st century, the disease spread through migratory birds from Southeast Asian countries to other countries such as Austria, Germany, Sweden, Czechoslovakia and Romania, Asia, South and North America , Africa. Bird flu in Russia was discovered in 2005, it was introduced by wild migratory birds and outbreaks of the disease affected the Novosibirsk, Omsk, Tyumen, Kurgan, Chelyabinsk regions and the Altai Territory. Kalmykia, the Tula region, Türkiye and Romania were the next to suffer from the virus.

The first avian influenza virus in humans was recorded in 1997 in Hong Kong.

What is the danger of the disease

This type of influenza is extremely dangerous for humans, microorganisms are very contagious and cause serious damage to the lungs, the virus can affect the liver, kidneys, and brain. In addition, it is insensitive to interferon drugs, Remantadine, and has a tendency to mutation, which makes it even more dangerous. The mortality rate from the disease is quite high and amounts to 50-80%.

How is bird flu different from regular flu?

Symptoms in humans initially resemble those of the common flu. A runny nose, cough appears, the body temperature is elevated, the person becomes weak and lethargic. But the consequences of the disease are very severe, most cases are fatal.

Therefore, if even one bird on a farm gets sick, the entire population is destroyed to avoid serious consequences.

Transmission routes

The source of infection is wild waterfowl. They themselves do not get sick. Being in reservoirs with stagnant water, birds with feces leave a virus there, which through the water infects waterfowl, and then the rest that are on the farm.

The virus is transmitted to humans by airborne droplets. When poultry coughs, droplets of mucus or saliva are released. By inhaling them, a person becomes infected. The virus can be transmitted through contact, through touching objects that have secretions from a sick bird on them.

The virus is able to survive for many years at temperatures below minus 70 ° C, which means it can survive in frozen meat. The past is safe, the virus dies at +70 ° C, in addition, it cannot withstand repeated repeated freezing (more than 5 times).

There is a high risk of catching the virus among people working on poultry farms and among rural residents raising poultry. Children, pregnant women and the elderly are also at risk.

Main features

It can occur in two different forms. The first option does not have serious consequences. A bird that is sick stops laying eggs, has a cough, and its feathers become ruffled. The second option, in which the respiratory and digestive organs are damaged, ends in death.

How does bird flu manifest in humans? Symptoms in people at the initial stage are similar to those of a common cold or flu, but very quickly turn into pneumonia. The disease often ends in death.

The incubation period ranges from one to seven days. The disease has an acute onset - with high fever, pain in muscles and joints. The temperature (about 38 °C) lasts 10-12 days, in severe cases it persists until death.
Laryngitis, rhinitis, bronchitis appear on the 2-3rd day, severe sore throat occurs. Along with such symptoms, viral pneumonia develops with a disease such as bird flu.

Symptoms in people can be not only intoxication and catarrh. Very often the gastrointestinal tract is also affected, which is accompanied by vomiting, diarrhea, and abdominal pain. Bleeding from the nose or gums may occur. A person who is sick with bird flu will feel worse very quickly.

Diagnostics

Professional medical assistance is required at the slightest suspicion of bird flu. Symptoms in humans that arise after contact with a sick bird or person are a reason to immediately consult a doctor. The therapist will examine and interview the patient, and also prescribe additional studies. When listening to the lungs, if pneumonia has begun to develop, hard breathing is detected, and there are moist rales. An X-ray examination reveals a rapidly spreading infiltration.

In a general blood test, with this disease there is a decrease in the number of leukocytes, lymphocytes and platelets. To make an accurate diagnosis, in addition to a blood test, it is necessary to take a nasal swab.

A sick person may have an enlarged liver and may develop kidney failure.

How to treat?

Treatment of bird flu takes place in the infectious diseases department of the hospital, where the person will be prescribed symptomatic therapy. The most commonly used antiviral drug is Tamiflu, which was used effectively during the epidemics of 2008 and 2009.

A less weak but effective bird flu is Arbidol, which is prescribed in a higher dosage, which ensures maximum antiviral effect. Medicines containing paracetamol (Ibuprofen, Nise, Efferalgan) help to cope with fever and fever. Preparations that contain interferon, which is necessary for the patient.

Equally important is complete isolation of the patient, which prevents infection of surrounding people. A sick person must have individual personal hygiene products, bed linen, clothing, dishes, etc. In the acute period of the disease, it is necessary to frequently rinse the upper respiratory tract to get rid of accumulated mucus. In addition, the patient needs to adhere to a strict diet, eliminating or limiting fried, spicy and sour foods.

Prevention

In order to avoid infection, you must:

Avoid contact with wild birds.
Children should be prohibited from being hand fed.
At the slightest sign of illness in poultry, they must be destroyed by reporting the incident to a veterinary clinic.
If you discover a dead poultry, you must immediately bury it, wearing a thick mask, protective clothing and gloves.
If you have poultry, be sure to thoroughly wash your hands regularly.
It is necessary to undergo a course of preventive procedures in a medical institution when going to the territory where avian influenza was discovered. Prevention includes vaccinations and antiviral medications.
Although cases of infection after eating chicken have not been officially registered, it is necessary to remember precautions when preparing poultry and egg dishes. Thorough heat treatment helps destroy the virus.

If you find even the slightest signs of bird flu, contact us as soon as possible. Timely and qualified medical care will save your health, and in severe cases, even life.

Performed by Alena Ivanyuk

Poultry influenza(Grippus (influenzae) avium, classical bird plague, European bird plague) is a highly contagious, acute disease characterized by septicemia, damage to the respiratory and digestive organs.

Historical reference. The disease called “exudative typhus of chickens” was first described in 1880 in Italy by Perroncito. From Italy, the disease was repeatedly brought into various European countries and was registered under different names, including European, or classical, bird plague. In 1924 - 1925 pp. Bird plague has become widespread in the United States and has been recorded for many decades in South America, North Africa, Palestine, Egypt, Japan, Korea, Israel, Australia, India, the Philippines, and Ceylon. The viral nature of the disease was identified by Centanni and Savunotsi back in 1901, and in 1956 Schaeffer and Waterson established the identity of the classical fowl plague virus and the influenza virus type A. After 1971, the classical fowl plague began to be called “bird flu”, and in 1979. a new unified classification was adopted for all pathogens of animal and human influenza based on the structure of hemagglutinin and neuranimidase, without taking into account the natural host from which the virus was isolated.

Nowadays, bird influenza in the form of a class plague is rarely recorded; more often this infection is caused by serovars of the A virus with low pathogenicity than the original influenza A virus. The economic damage caused by the disease was extremely large in the past and was caused by widespread distribution, mass death of birds and material losses in due to quarantine, which completely disrupted the economic life of the economy. During the epidemic of fowl plague in Ukraine in 1944, more than 900 thousand sick chickens died and were destroyed (I. I. Lukashov, 1963). A significant role in the elimination of this disease belongs to the Ukrainian scientists I. M. Doroshko and M. I. Gorban.

The causative agent of the disease- RNA genomic virus from the Orthomyxoviridae family, genus of influenza A viruses, subtypes A5 and A7. It has a spherical or filamentous shape, size 80 - 120 nm, reproduces well in chicken embryos, primary cultures of chicken embryo fibroblast cells. It agglutinates the erythrocytes of chickens, rabbits, guinea pigs and, unlike the Newcastle disease virus, it also agglutinates the erythrocytes of sheep and horses. In the body of sick and recovered chickens, it causes the formation of hemagglutinous, virus-neutralizing and complement-producing antibodies. Based on surface antigens (hemagglutinin H and neuraminidase N), type A viruses are divided into 13 antigenic subtypes. Diseases in the form of classical fowl fever are caused by only two subtypes of the avian influenza virus - A5 and A7. Other antigenic subtypes have significantly less pathogenicity for chickens and cause only a respiratory form of the disease in young birds. In ducks, the disease is caused by influenza virus subtypes A1, A2, A3, A4 and A6.

The influenza A virus is unstable in the external environment and is quickly destroyed by various disinfectants. At a temperature of 55 ° C, the virus is inactivated after 1 hour, at 60 ° C - after 10 minutes, at 65 - 70 ° C - after 2 - 5 minutes. At low temperatures (minus 30 ° C) and in a lyophilized state, it remains viable for up to 2 years. The infectivity and hemagglutinous activity of the virus at - 60 ° C lasts up to 2 years, at + 4 ° C - for several weeks.

Epizootology of the disease. The influenza A virus affects chickens and ducks of all ages, as well as 15 other bird species, including turkeys, guinea fowl, pheasants, geese, rooks, jackdaws, and sparrows. The source of the infectious agent is sick hens and chickens that release the virus into the external environment with eggs and all secrets and excreta, as well as virus-carrying birds that have recovered from illness for 2 months. Factors of transmission of the virus can be premises, bedding, nests, paddocks, various care items contaminated with secretions of an infected bird, as well as corpses, carcasses of slaughtered birds, non-neutralized slaughter waste, eggs, down and feathers of sick birds. The spread of the disease is facilitated by synanthropic and wild birds, rodents, insects, vehicles, as well as various violations of quarantine rules. Infection of poultry occurs by airborne droplets, as well as orally through contamination of water and feed with the pathogen.

In the case of a primary occurrence on a farm, influenza occurs among chickens in the form of an epizootic, which over the course of 30 - 40 days covers almost the entire susceptible poultry population, with high mortality, which is 80 - 100%. With the constant introduction of new susceptible chickens into the herd, systematic outbreaks of infection occur and the formation of an inpatient department. In farms unaffected by influenza, hens and chicks often suffer from respiratory mycoplasmosis, colisepticemia, and infectious laryngotracheitis.

Pathogenesis. From the point of entry into the body, the virus quickly enters the bloodstream, causes viremia, and is carried by the blood into the cells of various organs and tissues. Damage to the walls of blood vessels causes hemodynamic disturbances, predetermines exudative phenomena and hemorrhagic diathesis. Hypoplasia of lymphoid organs, singing lymphocytes and a sharp inhibition of the body's defense mechanisms cause a generalized form of infection and the rapid death of the bird.

Clinical signs and course of the disease. The incubation period lasts 1 - 5 days. The course of the disease is acute and subacute, which depends on the antigenic subtype of the virus causing the disease and its virulence. Chicken flu, caused by a virus of subtypes A7 and A5, is acute and manifests itself in the septic form characteristic of the classical (European) plague. There is an increase in body temperature to 44 ° C, refusal to feed, depression, loss of sensitivity, cyanosis of the mucous membranes, comb and earrings, paresis and paralysis. The sick bird sits, ruffled, resting its beak on the floor, wings drooping, gait unsteady. Before death, body temperature drops to 30 ° C. Some sick chickens may exhibit symptoms of damage to the nervous system or digestive tract, swelling of the subcutaneous tissue in the head and neck area. Mortality ranges from 70 to 100%.

In the case of chicken influenza caused by a virus of subtype A1, the respiratory form of the disease is determined, the degree of manifestation of which depends on the virulence of the strain, the presence of secondary infections, the age and conditions of keeping the bird. There is an increase in body temperature to 44 ° C, sneezing, difficulty breathing, wheezing, shortness of breath, cyanosis of the ridge, earrings, conjunctivitis, lacrimation. A sick bird loses its appetite, its feathers are protruding, its head and wings are drooping, and mucus is leaking from its beak. Mortality is 70 - 90%. In some birds, ataxia, tremor and other signs of damage to the nervous system appear. In adult birds, there is a decrease or cessation of egg production, which can occur in the absence of symptoms of respiratory damage. For the respiratory form of the disease, the mortality rate does not exceed 20%.

Influenza virus subtype A6 causes an epizootic among adult birds with primary damage to the digestive tract. With the enteritis form, there is a refusal to feed and a decrease in egg production; the bird becomes inactive, lethargic, feathers are ruffled. Thirst, diarrhea, and stool are foamy and greenish-yellow in color, sometimes mixed with blood. With this form of the disease there is a high morbidity, but the mortality rate does not exceed 5 - 15%.

Pathological changes. They depend on the biological properties of the virus subtype, which leads to the death of the bird. With influenza A5, phenomena of hemorrhagic diathesis and swelling of the subcutaneous tissue in the head, neck, and dewlap areas are observed. In all body cavities and the cardiac membrane, accumulation of a significant amount of turbid exudate is detected. The muscles are bluish, with speckles and striped hemorrhages. Hemorrhagic enteritis and peritonitis, hemorrhages into the stroma of the follicles are also detected.

Influenza A7 diseases result in hemorrhages in the serous tissues, parenchymal organs, skeletal muscles, and gastrointestinal tract. Necrotic lesions of the spleen, liver, and kidneys are characteristic. The membranes of the brain are hyperemic and edematous; under the dura mater there are diffuse hemorrhages and sometimes foci of necrosis.

Influenza A1 disease is accompanied by catarrhal sinusitis, rhinitis, tracheitis, pharyngitis, interstitial pneumonia, bronchitis, pericarditis. In some cases, lesions of the oviducts and ovaries are observed.

Influenza A6 virus causes gastroenteritis, hemorrhages in the gastrointestinal tract, peritonitis, deep ulcers in the small intestine, mainly in the duodenum. Striped hemorrhages are revealed under the cuticle of the muscular stomach; the cuticle is very difficult to remove. The goiter is filled with watery contents. The spleen is anemic, the liver, kidneys, serous membranes of the intestines are in a state of congestive hyperemia, the egg follicles are deformed, softened, with hemorrhages and hematomas.

Diagnosis is based on the analysis of epidemiological data, clinical signs of the disease, pathological changes and laboratory test results.

Laboratory diagnostics. Includes virological studies of pathological material taken at the acute stage of the disease, conducting a bioassay on chickens, as well as the study of paired blood sera with an interval of 5 - 7 days. For retrospective diagnosis, serological studies of blood sera from recovered birds are carried out. Swabs from the nasopharynx and cloaca are sent to the laboratory for a definitive diagnosis; after death - whole corpses or trachea, lungs, liver, brain, air sacs, intestines. Indication of the virus in pathological material is carried out by GPD in an infected chicken embryo fibroblast cell culture or RIF, RGA with a 1% suspension of chicken erythrocytes. At the same time, cytoscopy of thin smears-imprints from the mucous membrane of the upper respiratory tract, stained according to the Romanovsky, Pigasky or Bykovsky method, is carried out. In positive cases, cytoplasmic inclusion bodies of violet or bright red color are clearly visible in the studied preparations. In laboratory practice, to indicate the influenza virus in smears from various tissues, hatching eggs, infected chicken embryos and cell cultures, the immunofluorescence reaction is often used, with the help of which the viral antigen is detected even if it is not possible to isolate the pathogen from the affected tissues. To isolate the influenza virus, 9-11-day-old chicken embryos are used, into which pathological material is injected into the allantois or amniotic cavity.

All subtypes of the virus, with the exception of A6, cause the death of chicken embryos after 26 - 36 hours. Identification of isolated influenza virus is carried out by RZGA with the amniotic fluid of infected chicken embryos. Reproduction of the avian influenza virus in cell cultures is possible only after 2 - 5 previous passages in chicken embryos; GPA is determined after 24 - 28 hours using RGA and RGADA.

When conducting a bioassay, a suspension of pathological material is administered to 2-3 month old chickens subcutaneously or intramuscularly. In the presence of avian influenza virus subtypes A 1, A7, A5, infected chickens die within 36 - 72 hours. Serological diagnosis of avian influenza is carried out using RTGA with known avian influenza viral antigens, as well as with local strains. The research results are considered positive when the serum titer in the second sample, taken 10 days after the onset of the disease, increases by at least 4 times.

Differential diagnosis. Provides exclusion of Newcastle disease, infectious bronchitis of birds, infectious laryngotracheitis of birds, respiratory mycoplasmosis of birds. To do this, first of all, a diagnostic set of viral antigens and corresponding specific antisera are used. During Newcastle disease, diarrhea is very common, but swelling of the subcutaneous tissue almost never occurs. Fibrinous deposits and ulcers are found in the large intestine, which is typical only for this disease. The spleen and liver have no visible pathological changes. Hyperimmune serum against Newcastle disease virus only agglutinates erythrocytes treated with a homologous virus, and does not aglutinate erythrocytes sensitized with avian influenza virus.

Infectious bronchitis is enzootic, affecting mainly chickens, and the mortality rate is low. Infectious laryngotracheitis differs from avian influenza by clearly defined symptoms of respiratory damage, the absence of RHA with a suspension of pathological material from a sick bird and with the amniotic fluid of infected chicken embryos. The infectious bronchitis virus causes a typical pathology of infected chick embryos, and the infectious laryngotracheitis virus causes visceral lesions of the chorion-allantoic membrane. Respiratory mycoplasmosis is differentiated using special serological tests. No treatment has been developed.

Immunity. After having the flu, he is not sterile. For specific prevention, attenuated or inacti-Vovan vaccines are used against the subtype of avian influenza virus that causes the disease. For prophylactic vaccination against influenza A virus of birds of subtype H7 N1, which causes classical fowl fever, live vaccines from attenuated strains Ru and P are used. In order to prevent influenza A of birds, which is caused by viruses of subtypes A1 - A8, an inactivated vaccine is used. The intensity of immunity must be monitored using the RZGA on the 21st - 30th day after vaccination. If antihemaglutinin titers of at least 1:10 are established in 80% of the studied vaccinated birds, immunity is considered sufficient for preventative prevention of the disease.

Prevention and control measures. To prevent the introduction and spread of the pathogen, it is necessary to carefully comply with veterinary and sanitary standards for the maintenance and care of poultry. Particular attention should be paid to veterinary supervision when importing eggs for incubation and chickens only from farms free from infectious diseases, keeping them in isolation, regular mechanical cleaning of poultry houses and the area around the farm, and ongoing disinfection. They also control the quality of disinfection of transport, returnable containers and the safety of imported feed.

When establishing bird flu, it is advisable to slaughter the entire disadvantaged group. The carcasses of sick and suspected birds, as well as the corpses of dead birds, are burned. Conditionally healthy birds are slaughtered for meat, the carcasses are boiled at 100 ° C for 30 minutes and sold only on this farm. Feathers and down obtained from the slaughter of relatively healthy birds are dried in drying units at a temperature of 85 - 90 ° C for 15 minutes. If there is no drying installation, down and feathers are disinfected in any suitable containers with a 3% hot (45 - 50 ° C) formaldehyde solution for 30 minutes and then dried. In poultry houses, thorough mechanical cleaning is carried out, low-value wooden equipment (feeders, perch), leftover feed and manure are burned, and all poultry houses and the area around them are disinfected.

To disinfect poultry houses, use a 3% hot (70 - 80 ° C) solution of caustic soda with an exposure of 3 hours, a 1% solution of formaldehyde with an exposure of 1 hour, a clarified solution of bleach containing C% active chlorine with an exposure of 3 hours . Disinfection is also carried out with aerosols containing an 8-10% solution of formaldehyde (15 ml/m) or a 20% solution of peracetic acid (20 ml/m) with an exposure of 6 hours.

In a healthy farm, substandard and unproductive birds are systematically culled. Aerosol disinfection of premises is carried out in the presence of birds using highly dispersed aerosols of lactic acid or chloroturpentine. Eggs for incubation are imported from farms affected by influenza. Each batch of exported young animals is raised in a room completely freed from the previous birds, cleaned and disinfected, located in a safe poultry house. Upon reaching 45 days of age, chickens are vaccinated with an inactivated vaccine.

Birds, like people, get the flu. Influenza viruses infect birds, including chickens and poultry, as well as wild birds such as ducks.

Most avian influenza viruses only infect birds. However, avian influenza can pose a risk to humans. The first case of human infection with the H5N1 virus occurred in 1997 in Hong Kong. Since then, the bird flu virus has spread to birds in Asia, Africa, the Middle East and Europe.

Avian influenza is a disease caused by strains of the influenza virus that primarily affects birds.

In the late 1990s, a new strain of avian influenza emerged and was seen to cause severe illness and death, especially in poultry such as ducks, chickens or turkeys. As a result, this strain was named highly pathogenic (that is, very dangerous and contagious) avian influenza and was given the term H5N1.

There are 16 different types of bird flu. The H5N1 strain is of greatest concern because it is the most contagious and the most deadly. Fortunately, this virus is very difficult for people to get infected with.

A relatively new strain of bird flu has been discovered in China. The influenza A virus was named H7N9 (H7N9 Chinese avian influenza). On March 31, 2013, the identification of the H7N9 virus was reported; the new strain differed in antigenic composition from the H5N1 avian influenza virus. Unfortunately, the H7N9 strain of avian flu appears to be genetically unstable.

Since its discovery in 2013, at least 48 different subtypes of H7N9 have been identified. As some H7N9 viruses persist in chicken farms in China, researchers fear that their strains will continue to exchange genes with other influenza viruses, which could start a new pandemic.

Since the discovery of the highly pathogenic influenza, infected birds have been found in Asia, Europe, Africa and the Middle East. Careful control measures, including eradication of infected flocks of birds and vaccination of healthy animals, have reduced the number of cases, but the virus continues to exist among domestic birds in regions of Asia and Africa. In 2007-2008, there was a small outbreak in Bangladesh and Pakistan associated with contamination of domestic chickens.

In March 2015, avian influenza was detected in several turkey flocks in the United States. This has led to a number of countries banning the import of American poultry products.

Similarly, in March 2015, avian influenza was discovered in chickens in Holland. Most experts believe that poultry become infected with avian influenza due to contamination from wild bird feces.

As of March 2015, no human cases of avian influenza have been detected in the US population. Although the H1N1 swine flu virus that caused the pandemic contains some avian flu genes, it was not the original H5N1 virus.

The virus spreads among birds due to the fact that infected birds secrete it into their saliva, nasal secretions and droppings. Healthy birds become infected when they come into contact with contaminated secretions or droppings from sick animals.

Contact with contaminated surfaces (such as a cage) can also allow the virus to spread from bird to bird. Symptoms in birds can range from mild (eg, decreased egg production) to multiple critical organ failure and death.

First human case of the disease, which developed from infection with highly pathogenic avian influenza, was discovered in 1997. From then until 2016, according to the World Health Organization, 846 people were infected with the H5N1 virus, of whom 449 died.

Human cases of highly pathogenic avian influenza have most often been observed in Southeast Asia and Africa. Mutations have occurred frequently in the virus, and it is possible that some of these mutations could create a more contagious virus that could cause a regional epidemic or worldwide pandemic of avian influenza in humans.

Fortunately, mutations occurring so far have not made the virus more infectious, although concerns about this remain. The discovery of the H7N9 strain of avian influenza is causing concern.

Four people in China have been infected with the H7N9 virus, two of whom have died. Health officials around the world are concerned about the possibility of a strain of bird flu that could easily spread from birds to humans. Although mild transmission between humans has not yet developed, H7N9 avian influenza infected 707 people, of whom 277 died. Most of these infections were associated with contact with infected birds or their droppings.

Table. Number of confirmed cases of avian influenza A H5N1, according to the World Health Organization, 2003-2015

A country	Total cases	Died
Azerbaijan	8	5
Bangladesh	8	1
Cambodia	56	37
Canada	1	1
China	53	31
Djibouti	1
Egypt	346	116
Indonesia	199	167
Iraq	3	2
Lao People's Democratic Republic	2	2
Myanmar	1
Nigeria	1	1
Pakistan	3	1
Thailand	25	17
Türkiye	12	4
Vietnam	127	64
TOTAL	846	449

What is the cause of bird flu?

Bird flu is caused by strains of the influenza virus that have evolved to be specifically adapted to invade bird cells.

There are three main types of flu:

The virus that causes avian influenza is influenza A, which contains eight strands of RNA that make up its genome.

Influenza viruses are classified based on the analysis of two proteins on their surface - hemagglutinin (H) and neuraminidase (N). There are many types of hemagglutinin and neuraminidase proteins.

For example, the recent pathogenic avian influenza virus possessed hemagglutinin type 5 and neuraminidase type 1. Thus, it was named “H5N1” influenza A virus.

The 2013 virus had different surface proteins, H7 and N9, hence the name H7N9. Other types of avian influenza include H7N7, H5N8, H5N2 and H9N2.

There are many types of influenza viruses, most of them prefer to live in a limited number of animals. Thus, swine flu primarily infects pigs, and avian flu primarily infects birds. Human flu strains are best adapted to humans.

A small number of cases of infection can occur through incidental hosts, for example when people come into close contact with infected birds and become infected with avian influenza. In addition to humans and birds, it is known that pigs, tigers, leopards, ferrets, domestic cats and dogs can sometimes be infected with avian influenza viruses.

Influenza viruses mutate frequently and easily. These mutations can occur spontaneously in one virus or can occur when two different strains exchange genetic material. Influenza viruses have two main types of mutations:

antigenic shift, when large segments of RNA change places between different types of influenza viruses;
antigenic drift, when small RNA sequences change places.

Antigenic shift is usually responsible for the emergence of new strains.

For example, the 2009 swine flu pandemic was caused by a virus that incorporated genetic material from swine, bird and human flu strains. New mutations could allow the virus to evade the immune system and render old vaccines ineffective.

In 2011, one strain of a highly pathogenic avian influenza virus mutated in this way, making the existing vaccine used against avian influenza ineffective against the new strain. Sometimes the influenza virus mutates in such a way that it becomes capable of infecting new species of animals.

Serious influenza pandemics occur when a relatively new strain of influenza virus emerges that is highly contagious to people. The deadliest pandemic in modern history was the 1918 flu (also known as the Spanish flu, although it did not originate in Spain).

The 1918 virus quickly spread and killed tens of millions of people around the world. Mortality was particularly high among young, healthy adults. Although the 1918 virus was a human influenza virus, it had many genes that likely came from a strain of avian influenza. One of the reasons why health authorities are closely monitoring and trying to limit human exposure to sick birds is to try to reduce the chances of new strains emerging that may have the ability to thrive in human tissue.

What are the risk factors for developing avian influenza?

People can become infected with avian influenza through contact with infected birds (such as chickens) or their infected droppings or secretions.

Risk factors include caring for sick birds, killing sick birds and preparing them for consumption. Despite the huge number of people who come into contact with birds every day around the world, human cases of avian influenza remain rare.

This highlights how difficult it is for the avian influenza virus to infect human cells, but that difficulty may be reduced by mutations such as antigenic shift. The H1N1 swine flu pandemic that began in Mexico is an example of such a mutation.

Although direct contact with sick birds poses the highest risk of developing avian influenza, indirect exposure to bird droppings or other products (such as eggs) is also dangerous. Contact with unwashed eggs from sick birds or water contaminated with their droppings poses a potential risk of developing the disease.

Transmission of the virus from person to person has occurred in isolated cases. Therefore, caring for a person infected with avian influenza is also a risk factor for developing the disease.

There is a theoretical risk for laboratory workers who work with avian influenza viruses. In one case in 2009, a company inadvertently sent live avian influenza samples to a research laboratory, which were then used to vaccinate ferrets. This contaminated vaccine did not cause human disease.

Is it possible to get infected from another person?

Sometimes - after personal contact - a patient with bird flu can infect another person.

In 2006, 8 members of one family fell ill with bird flu in Indonesia, and 7 of them died. Why this happened is not known exactly. Family members most likely came into contact with infected birds. They also may have shared genes that made them especially susceptible to the virus.

What about bird flu that has been genetically modified in the laboratory?

In the fall of 2011, Dutch scientists made a stunning announcement. They genetically altered the H5N1 virus so that it spreads through the air among ferrets.

Why were ferrets chosen? Almost all human influenza viruses spread easily among these animals, which is why they are often used in scientific research.

Scientists in the US also created a mutant strain of H5N1 that spread among mammals.

These studies showed that the H5N1 virus has the potential to become dangerously transmissible among mammals, including humans.

Scientists have not released important information about creating mutant viruses; these details are available only to qualified researchers.

But these studies have caused very pronounced controversy. Some scientists say that mutant viruses cannot be created, since they can escape beyond the boundaries of laboratories. In 1977, the H1N1 flu broke out on the border between Russia and China and was considered lost. Although officials deny it, many scientists believe the virus spread from a laboratory.

What are the symptoms and signs of bird flu?

Symptoms appear approximately 2-8 days after infection. Infected people suffer from common flu symptoms, which may include:

Increased temperature (above 38° C).
Cough (usually dry, without sputum production).
A sore throat.
Muscle pain.
Nausea.
Vomit.
Diarrhea.
Headache.
Joint pain.
Lethargy.
Nasal discharge (runny nose).
Insomnia.
Eye infections.

In children, the symptoms are similar. This viral infection can progress to pneumonia and respiratory failure. Bird flu causes a very aggressive form of pneumonia (acute respiratory distress syndrome or ARDS) that is often fatal.

How do doctors diagnose bird flu?

Routine tests for human influenza A will be positive in patients with avian influenza, but they are nonspecific. To establish an accurate diagnosis of avian influenza, specialized tests must be performed. The virus can be detected in sputum using several methods, including cell culture or polymerase chain reaction (PCR). The growth of the virus in cell culture is carried out in laboratories that have the appropriate biosafety certification. PCR detects influenza A virus nucleic acid. Specialized PCR detects avian strains.

During and after infection with bird flu, the body produces antibodies against the virus. Blood tests can detect these antibodies, but this requires one blood draw early in the disease and a second one several weeks later. Therefore, results are usually available after the patient has recovered or died.

How to treat bird flu?

Due to the small number of human cases, scientific research into the treatment of avian influenza has not been possible.

It is believed that the best way to prevent the development of bird flu is to avoid contact with sick birds and their droppings. People are advised not to touch any sick or dead bird. The World Health Organization currently recommends oseltamivir (Tamiflu) and zanamivir (Relenza) for the treatment and prevention of avian influenza. These drugs can suppress viral replication and improve patient outcomes, especially survival rates.

For best results, Tamiflu should be taken within 48 hours of the onset of symptoms. But, since the mortality rate from bird flu is very high, doctors should prescribe oseltamivir to patients who were diagnosed later.

For severely ill patients, doctors may increase the recommended daily dose or prolong treatment. It should be borne in mind that drug absorption may be severely impaired in patients with severe gastrointestinal symptoms.

Patients with known or suspected avian influenza should remain at home or be hospitalized (isolated from other people).

Although Tamiflu and Relenza can be effective drugs in treating influenza caused by the H5N1 avian influenza virus. However, more research is needed to demonstrate their effectiveness.

Scientists from the United States and China have reported cases of drug resistance in human H5N1 viruses.

Patients should:

rest;
drink enough fluids;
to eat well;
take medications for pain and fever (prescribed by a doctor).

Patients infected with the H5N1 virus often develop complications such as bacterial pneumonia. They require antibiotics and some need supplemental oxygen.

What are the complications of bird flu?

Complications of bird flu include:

shortness of breath;
pneumonia;
acute respiratory distress syndrome (ARDS);
lung collapse;
mental state disorders;
convulsions;
failure of organs and systems;
death.

Unfortunately, patients infected with avian influenza often have one or more of the complications listed above. Mortality rates for the H5N1 strain are approximately 55% and for the H7N9 strain approximately 37%.

What is the prognosis for bird flu?

In human cases of avian influenza, the prognosis remains poor. Many cases of the disease developed in poor people living in rural areas of underdeveloped countries who did not have access to modern intensive care units or antiviral treatment.

Approximately 55% of people diagnosed with H5N1 avian influenza died from the disease; the H7N9 strain has similar mortality rates - 37%. Survivors may have long-term health problems if organs and their systems are severely damaged.

Prevention of bird flu

There is currently no way to stop the spread of bird flu - it is a virus carried by birds, including wild birds that migrate. Understanding bird migration and monitoring their movements provides health and agricultural authorities with the data they need to protect people and pets.

Vaccination– There is a vaccine for human seasonal influenza, but not for avian influenza. Various laboratories around the world, as well as pharmaceutical companies, are working on a bird flu vaccine.

In 2007, the first human vaccine against the highly pathogenic avian influenza virus was approved in the United States. This vaccine was made from inactivated viruses and did not contain live ones.

It stimulates the immune system to produce antibodies against avian influenza, which presumably can protect humans from this disease. The vaccine was purchased by the US government and included in the Strategic National Stockpile. It has not been made available to the general public because the United States does not currently have problems with the highly pathogenic avian influenza virus.

Side effects of the vaccine include arm pain, fatigue, and temporary muscle pain. The vaccine has not been tested in large numbers of people, so there may be other side effects that have not yet been discovered. The vaccine is effective against the strain that caused large outbreaks of bird flu, but it does not work against the newly mutated strain discovered in 2011. It is unlikely to provide protection against the new H7N9 avian influenza.

Scientific research into influenza vaccines continues. New developments targeting relatively immutable influenza virus antigens may result in a vaccine that protects against most (if not all) influenza viruses. If these studies are successful, potential future outbreaks of influenza, including avian influenza, could be reduced or prevented.

Each person can minimize the spread of influenza, bird flu and many other infections:

Hand hygiene - you should regularly wash your hands with warm water and soap, before and after using the toilet, and before preparing food. It is necessary to wash your hands after coughing.
When coughing, you should cover it with the inside of your elbow, not your hand. When you cough into your hand and then touch some things, the virus can remain on their surface and other people can become infected from them. If possible, it is better to use a tissue when coughing and then carefully dispose of it.
Sick people should stay away from public places and avoid contact with people.
When visiting a doctor, the patient must immediately be told in the emergency department that he needs to be isolated from other people. In some institutions, the patient may be given a surgical mask.
It is necessary to adhere to recommendations regarding vaccination against seasonal influenza and pneumococcal infection.

When cooking, do not use the same utensils for raw and cooked meat. Before touching raw poultry, wash your hands with soap and water. The same must be done after this.

Cooked poultry is safe to eat.

Do not go close to dead or sick birds.

What are the experts afraid of?

Currently, it is very difficult for a person to become infected with bird flu, and it is even rarer for one person to transmit this disease to another. Experts fear that if a person already sick with seasonal flu contracts bird flu, the H5N1 virus could exchange genetic information with the human H1N1 flu virus and gain its ability to spread from person to person. An easily transmitted strain of avian influenza virus between people can have devastating consequences.

Bird flu has a very high mortality rate, and if it becomes a pandemic, millions of people could die.

To infect humans, the H5N1 strain must penetrate deep into the lungs. This feature makes it more deadly, but also less infectious. People with an infection deep in the lungs cough and sneeze less than those with an upper respiratory tract infection.

A mutated virus can, for example, infect the upper respiratory tract, as well as the deep ones. Sick people will then shed more viruses through their coughs and sneezes, making it easier to infect others. People nearby will become infected more easily, since the virus will not need to penetrate deep into the lungs to cause illness.

Controlling avian influenza outbreaks helps reduce the chance that an avian influenza virus will come into contact with a human influenza virus and mutate. It is also important to monitor seasonal human influenza rates. The World Health Organization says quickly eliminating avian influenza outbreaks is a top public and global health priority.

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Avian influenza - (Grippus avium; highly pathogenic avian influenza, classical avian plague, chicken influenza A, exudative typhus, Dutch fowl plague) is a highly contagious, acute viral disease that affects agricultural, synanthropic and wild birds, affecting the respiratory and gastrointestinal tracts.

Avian influenza can occur in the form of epizootics, causing massive coverage of livestock and having a wide distribution - region, region, country.

Historical reference. The disease was first described in Italy in 1880. Perroncito, who differentiated it from fowl cholera and called it exudative typhus of chickens. The most severe epizootic occurred in 1925. in the north of the country, during which 200,000 chickens died. The disease subsequently spread to Austria, Germany, Sweden, Czechoslovakia and Romania. The disease was found in Asia, South and North America, and Africa. Influenza was first brought to Russia in 1902. The viral nature of the virus was established by the Italian scientist Gentania in 1902.

Currently, avian influenza in the form of classical plague, caused by subtypes of the virus with low virulence, occurs rarely, in the form of periodic epizootic outbreaks. Outbreaks of highly pathogenic avian influenza have been reported in many countries around the world since the beginning of the 21st century as a result of the spread of influenza by migratory birds from Southeast Asia. The highly pathogenic strain of the H5N1 virus was introduced into Russia by wild migratory and waterfowl in 2005, when outbreaks of avian influenza among domestic and wild animals were observed in the Novosibirsk, Omsk, Tyumen, Kurgan, Chelyabinsk regions and Altai Territory. Then the bird flu reached Kalmykia, the Tula region, Turkey and Romania.

Economic damage from avian influenza is extremely high and is associated with the massive death of sick birds, the costs of carrying out strict quarantine and veterinary and sanitary measures, including the destruction of sick birds. For example, the avian flu epidemic in the world in 2005 caused material damage estimated at 4 billion. Euro.

The causative agent of the disease– The RNA virus belongs to the orthomyxovirus family, which is divided into three serological types: A, B and C. Type A viruses cause disease in animals and humans. The size of viral particles is 80-120nµ. Influenza viruses, based on typing based on the main antigens (surface proteins) - hemagglutinin (H) and neuraminidase (N), are classified into 15 and 7 subtypes, respectively. They all have a certain relationship, but different serotypes cause diseases in different animal species. For birds, the most pathogenic viruses are subtypes H5 and H7, which have the molecular biological characteristics of highly pathogenic viruses. The H5N1 virus is of greatest concern due to its possible danger to humans.
In birds, the virus induces the production of virus-neutralizing and complement-fixing antibodies.

The persistence of the virus in the external environment varies depending on the serotype. The virus is sensitive to ether, chloroform, heat and acidic conditions (pH 3.0). At a temperature of 55°C it is inactivated within one hour, at 60°C in 10 minutes, at 65-70°C in 2-5 minutes. When deep frozen (temperature -70°C) in meat, the virus remains virulent for over 300 days. Drying the substrate containing the virus preserves it.

Common disinfectants: bleach, sodium hydroxide, phenol, hydrochloric acid, carbolic acid and others quickly inactivate the virus.

Epizootology. Influenza has been reported in many species of domestic and wild birds. The pathogenicity of the virus is not limited only to the bird species from which it was isolated. The Aj subtype virus was isolated from chickens, turkeys, pigeons, ducks, and geese, being pathogenic for rabbits, mice, guinea pigs, and humans, who develop atypical pneumonia in case of complications.
Several antigenic varieties of the virus, characteristic of humans, birds and domestic animals, can simultaneously circulate among wild and domestic birds. Stress reactions that occur in birds during their long flights and changing climatic conditions lead to an exacerbation of infection.

In industrial farms, the introduction of the infectious agent with feed, equipment, and inventory plays a certain role in the occurrence of the disease; undisinfected meat and egg containers pose a particular danger.

The first cases of the disease, as a rule, are registered in chickens and weakened adult birds against the background of their inadequate feeding, transportation, and overcrowded planting. Passages of the virus through the weakened body of chickens increase its virulence and contribute to subsequent illness in birds kept under normal conditions.

All susceptible birds on the farm usually recover from influenza within 30-40 days. This is explained by the high contagiousness of the virus and the high concentration of poultry in poultry houses.

The source of the infectious agent is a bird that has recovered from the disease (within 2 months). The influenza virus causes disease in birds through respiratory, oral, intraperitoneal, subcutaneous and intramuscular infection. In industrial enterprises with a cage system for keeping poultry, the main role in the spread of the pathogen is the aerogenic route, as well as the nutritional one (transmission through drinking water). The virus is released from the body of a sick bird in excrement, secretions, droppings, and hatching eggs. Rodents, cats, and especially free-living wild birds that enter or nest in poultry houses can take part in the spread of the influenza virus within poultry farms.

The presence of virus-carrying chickens maintains an epizootic focus on the farm during the reproduction of a new population of susceptible birds, which during rearing become ill and maintain stationary ill-being. The incidence of poultry varies from 80 to 100%, mortality from 10 to 90%, depending on the virulence of the virus and the conditions of keeping the poultry. In disadvantaged farms, influenza in chickens and chickens is often complicated by pathogens of respiratory mycoplasmosis, infectious laryngotracheitis, and colisepticemia. An adult bird loses its egg production by 40-60% within 2 months after illness. After contracting the flu, a bird partially or completely loses its immunity against,.

Pathogenesis. Depending on the virulence, tropism of the virus, and the natural resistance of the bird, a generalized or respiratory form of the disease develops.

As a result of the virus entering the mucous membranes of the respiratory tract, it begins to actively multiply and penetrates the circulatory system. All this happens within 4-12 hours. The virus is found in large quantities in blood serum and also in red blood cells. In the development of the disease, it is customary to distinguish four phases: active reproduction of the virus and its accumulation in parenchymal organs, viremia - the virus in this phase can be detected in the blood, then the process of synthesis of antibodies begins, which indicates the cessation of further reproduction of the virus. The last stage is accompanied by the active formation of antibodies and the formation of immunity in the bird.

Based on the fact that the virus releases toxic products during its life cycle, poultry in the viremia stage become intoxicated and die. This usually occurs during the acute course of the disease.

All highly virulent strains of the virus, regardless of belonging to one or another subtype, cause a generalized form of infection in poultry. With avian influenza caused by subtype A, hypoplasia of the lymphoid organs, lymphocytopenia and suppression of protective mechanisms occur, which contributes to viremia and virus replication in the cells of various organs and tissues. Due to impaired porosity of the walls of blood vessels and impaired hemodynamics, hemorrhagic diathesis is observed in sick birds.

Clinical picture. The incubation period is 3-5 days. Influenza can occur acutely, subacutely and chronically.
In acute cases, the bird refuses to feed (anorexia), the plumage becomes ruffled, the eyes are closed, the head is lowered, and the chickens lose egg production. Visible mucous membranes are hyperemic and swollen; in some sick birds, a viscous mucous exudate flows from the slightly open beak; the nasal openings are sealed with inflammatory exudate.

Some sick chickens experience swelling of the front part of the earrings due to congestion and intoxication of the body. The comb and earrings are dark purple. Breathing becomes rapid and hoarse, body temperature rises to 44°C, and before death drops to 30°C. If the disease in chickens is caused by highly pathogenic influenza viruses, then, as a rule, 100% of the chickens die.

Subacute and chronic course of influenza lasts from 10 to 25 days; the outcome of the disease depends on the resistance of the diseased bird. Mortality reaches 5-20%. With this form of influenza, a sick bird develops diarrhea along with respiratory symptoms, and the droppings become liquid and brownish-green in color. In addition to the above signs, the sick bird has ataxia, convulsions, necrosis, manege movements, and in the preagonal stage tonic-clonic convulsions of the muscles of the neck and wings.

In cases of infection with low-pathogenic strains, cases of chronic disease without pronounced clinical signs are possible.

Pathological changes. Depending on the course of the disease, pathological changes vary widely. The most typical symptom of influenza is a picture of hemorrhagic diathesis, accompanied by subcutaneous swelling in the pharynx, larynx, neck, chest, and legs, which contain gelatinous exudate. These edemas in birds occur as a result of dysfunction of the circulatory system. There are both massive and isolated hemorrhages under the skin, muscles, parenchymal organs and mucous membranes; in laying hens - hemorrhages in the ovary and oviduct.
Constant pathological signs of influenza are gastroenteritis, bronchitis, pericarditis, peritonitis, aerosaculitis, pulmonary edema, congestion in the internal organs.

Pathological changes in the brain are especially characteristic of influenza: hemorrhagic meningitis, diffuse hemorrhages, foci of edema in the softening of the brain matter.

During a histological examination of birds that died on the 3-4th day of illness, along with stasis and hemorrhages, we find degenerative changes in neurons and multiple areactive necrobiotic lesions in the gray and white matter of the brain.

Diagnosis. Based on the epizootic features of the course of the disease, characteristic acute clinical signs of respiratory disease and pathological changes, a presumptive diagnosis can be made. To make a final diagnosis, it is necessary to conduct a complex of laboratory virological studies.

Pathological material (liver, lungs, brain, etc.) from birds that died in the acute stage of the disease is sent to the laboratory. Pathological material must be fresh; it can be frozen to -60°C in order to preserve the virus or preserved in a 50% glycerin solution. For serological studies, paired blood sera are taken from chickens at different periods of the disease.

In the laboratory, methods of infecting chicken embryos are used to isolate the virus; to identify the isolated virus, RGA, RTGA and RSK are used. The biological test is performed on chickens 60-120 days old.
For retrospective diagnosis, RTGA, RDP, ELISA and PCR are used.

The diagnosis of avian influenza is considered confirmed if:

a highly pathogenic virus was isolated and identified;
any virus of subtypes H5 or H7 has been isolated and identified;
the presence of ribonucleic acid (RNA) specific for a highly pathogenic virus of any subtype or RNA viruses of subtypes H5 or H7 of any level of pathogenicity in samples of pathological material has been established;
antibodies to hemagglutinin subtypes H5 and H7 are detected when it is reliably known that they are not associated with vaccination.

Differential diagnosis. We differentiate the generalized septicemic form of influenza from. Respiratory form - from, and other respiratory diseases of birds.

Avian influenza, unlike Newcastle disease, affects all species of birds at any age and causes severe edema and catarrhal-hemorrhagic enteritis. The respiratory form of influenza is characterized by predominant damage to the upper respiratory tract; all types of poultry are affected, while infectious bronchitis affects only gallinaceae. Respiratory mycoplasmosis of chickens and infectious sinusitis of turkeys are characterized by a chronic course of the disease, the absence of acute inflammatory processes and the development of fibrinous-diphtheritic aerosaculitis.

Immunity and specific prevention. The recovered bird acquires non-sterile immunity, which lasts up to 6 months. To prevent highly pathogenic avian influenza in Russia, inactivated vaccines are used as the most epizootologically safe. For specific prevention, inactivated aluminum hydroxide hydroxylamine embryo vaccine type A, liquid and dry inactivated avian influenza vaccines are used. Vaccines are administered intramuscularly, inactivated - twice with an interval of 14 days. For preventive purposes, only clinically healthy poultry (chickens, ducks, turkeys) are vaccinated on endangered farms. 14-21 days after vaccination, the bird acquires intense immunity lasting up to 6 months.

Prevention. Owners of private farms must strictly comply with the “Veterinary rules for keeping birds on private farmsteads of citizens and open-type poultry farms” approved by Order of the Ministry of Agriculture of the Russian Federation dated April 3, 2006 No. 103 and registered with the Ministry of Justice of the Russian Federation on April 27, 2006 No. 7759. Owners of closed-type poultry farms (poultry farms ) must comply with the veterinary rules for keeping birds at poultry farms in accordance with the Appendix to the order of the Ministry of Agriculture of Russia dated April 3, 2006. No. 104, including basic veterinary rules for keeping poultry:

To prevent influenza, it is necessary to ensure that, before the departure of migratory waterfowl, the birds are exclusively housed in private household plots of citizens, where contact with wild waterfowl is not excluded during outdoor keeping.

Vaccination of birds kept in private household plots living in populated areas near which there are nesting reservoirs for wild waterfowl and shorebirds.

Carrying out measures to create unfavorable nesting conditions for waterfowl in reservoirs near populated areas.
The purpose of these measures is to scare birds away from their nesting sites. For this purpose, technical interference can be used - installing sound and light barriers and devices, covering local nesting sites with nets, mowing, as well as shooting waterfowl, semi-aquatic and synanthropic birds in reservoirs suitable for nesting.

The duration of the activities is from the moment the birds arrive until the end of the nesting period (April-June), as well as from the moment the departure begins until its completion (September-November).

Control measures. When avian influenza is detected on a farm in accordance with the order of the Ministry of Agriculture of the Russian Federation dated December 19, 2011. No. 476 “On approval of the list of contagious, including especially dangerous, animal diseases for which restrictive measures (quarantine) can be established.” By decree of the Governor of the region, a quarantine is established on the farm. Activities are being carried out in accordance with the Order of the Ministry of Agriculture of the Russian Federation dated March 27, 2006 No. 60 (as amended on July 6, 2006) “On approval of the Rules for the fight against avian influenza” (Registered with the Ministry of Justice of the Russian Federation on April 27, 2006 No. 7756). In a dysfunctional poultry house, sick or suspected birds are discarded, killed in a bloodless manner and disposed of. Conditionally healthy livestock are killed for meat. The premises are thoroughly disinfected.

In the event of the occurrence of avian influenza disease caused by highly pathogenic viruses in poultry farms (on farms), a special commission to combat avian influenza is approved, which introduces a strict sanitary regime for the operation of the farm; develops a set of measures aimed at eliminating and preventing the spread of the disease, which includes the destruction of carriers (migratory and waterfowl); the issue of vaccination in endangered areas and zones is being resolved; establishes deadlines for the reorganization and stocking of such farms with poultry, based on the specific conditions of the farm; resolves issues of possible protection of people from infection and their vaccination against human influenza.

Quarantine in an unfavorable point can be lifted no earlier than 21 days from the date of destruction (disposal) of all susceptible livestock or slaughter and processing of apparently healthy birds located in an unfavorable point and the final disinfection.
Quarantine in an organization that slaughtered poultry suspected of being infected with avian influenza or processed and stored products and raw materials from such poultry is canceled no earlier than 21 days after the end of poultry meat processing and the final disinfection of the organization’s premises, its territory, inventory, and production equipment.

After quarantine is lifted, the export of hatching eggs and live birds of all species and ages to other farms should be limited for all bird owners for 3 months.

Vaccination of poultry stock against avian influenza after quarantine is lifted should be carried out in the affected area for a period of time until the results of laboratory monitoring confirm the absence of virus circulation among the vaccinated stock.

Measures to protect personnel.

All persons involved in special activities to eliminate avian influenza disease are recommended to undergo a daily medical examination.

To work with sick birds, specialists must be provided with special clothing (robes or overalls, towels, hats), replacement shoes, rubber gloves, respirators, soap and other personal protective equipment, as well as the necessary tools and utensils. At the end of the work, clothes and shoes are disinfected or destroyed. After clinical examination of animals or sampling of pathological material, it is necessary to wash your face and hands with soap.

For personal disinfection of workers, instruments and utensils, they use means and methods prescribed for the disinfection of various objects contaminated with pathogenic microorganisms.

Persons who have suffered serious illnesses, those with diseases of the respiratory system, persons aged 65 years and under 18 years of age, and pregnant women should not be allowed to work with sick birds.