Symptoms of avian influenza in humans. Bird flu: the first symptoms in chickens, treatment and prevention

Bird flu is a viral infection that affects both birds and humans, and has a fairly high contagiousness. Sometimes this disease occurs with virtually no symptoms, but even in this case, the risk of complications and even death is quite high. The signs and causes of this disease, its treatment and prevention measures should be discussed separately.

Avian influenza is a viral infection that affects both birds and humans.

The main carrier of bird flu, as you might guess from the name of the disease, are birds. In most cases, we are talking about wild representatives of the bird family - especially waterfowl. These birds are constantly migrating and, therefore, carry the infection over fairly long distances. As for poultry, most often ill with this infection, these are turkeys and chickens.

For the first time, they started talking about the disease described in 1997, since it was then that a large number of people picked up the infection - the epidemic was recorded in Hong Kong and 60 percent of all cases eventually died. The virus received a scientific name - H5N1, and soon significantly expanded its geography, spreading not only in Asian and African, but also in European countries.

If earlier the infection was noted only in birds, now people began to suffer from it. Like other influenza viruses, it continued to mutate. 2003 in the Netherlands, for example, was marked by a small epidemic outbreak of H7N7, during which almost nine dozen people fell ill with this disease (and even one death was recorded).

2013 in China was marked by an outbreak of H7N9, when the disease was diagnosed in 130 people, about three dozen of whom died. According to WHO statistics, in the fall of 2013, the H7N7 virus was detected on some Italian farms - several hundred thousand poultry had to be slaughtered.

In China, the H7N9 virus, which is considered pathogenic for humans, is often noted. But an epidemic of bird flu is capable of starting in every country and on any continent, so the danger of this disease should not be forgotten - especially since the virus does not stop mutating, becoming more and more complex and adapting to ways to fight against it.

Features of the virus

Before talking about the symptoms of avian flu, you should tell more about this infectious family. The viral structure turns out to be quite complex: the outer shell consists of RNA and two proteins (neuraminidase and hemagglutin):

• For example, hemagglutin attaches a viral agent to a healthy cell and produces antibodies that protect the virus.
• Neuraminidase helps the infection to penetrate into a healthy cell and begin to multiply in it.

Scientists managed to identify several antigenic types of this pathogen: H7N7 causes the development of "chicken plague". As for H5N1, it causes mass death of chickens. That is, these types are considered the most pathogenic for poultry (after infection, all sick people die within two days). But, however, there are also low-pathogenic strains that are more or less easily tolerated by patients.

How pathogenic is avian influenza in humans? The mutation of these viruses has made them dangerous for humans. Moreover, rather severe forms of the disease are diagnosed: sometimes it even happens that death occurs with a lightning-fast course.

The infection is localized in the intestines, and goes out along with feces.

As for the mechanics of infection, it is aerogenic, that is, airborne. Quite often, the cause of infection is contact with an infected bird. Moreover, not necessarily with the living, but also with the dead. But people do not transmit the described infection among themselves (at least, to date, such cases have not been registered).

The infection is localized in the intestine

How does the disease manifest itself in birds?

The symptoms of this infection in chickens, turkeys and other birds, as well as in humans, should be discussed separately. So in chickens that have caught this infection:

• egg production is sharply reduced;
• anorexia is possible (since appetite completely disappears);
• getting worse appearance(for example, feathers look ruffled);
• inflammation of the mucous tissues begins;
• secreted mucus clogs the airways;
• the bird suffers from wheezing and intermittent breathing;
• temperature indicators increase (up to 44 degrees);
• diarrhea begins - and the color of the litter is brown-green;
• seizures may develop;
• there is a danger of neurosis.

First of all, the symptoms of bird flu in chickens relate to damage to the nervous system, as a result of which coordination of movements is disturbed. Birds stagger, it is difficult for them to step on their hind limbs, frequent falls are possible. The wings and necks are bent, acquiring an unnatural position. The bird ceases to respond normally to certain stimuli from the outside. They are tormented by intense thirst. There is a real danger of pulmonary edema, which, in turn, can end in death. The described disease is also called chicken influenza infection, although in turkeys it manifests itself even more often than in chickens, according to statistics. Birds such as geese, pigeons, ducks and so on are also susceptible to it.

Symptoms and danger of the disease

Is bird flu dangerous for humans? Undoubtedly. How? First of all, dangerous consequences.

The incubation period of this disease is usually 3 days, but in some cases it reaches 8 days and even a couple of weeks.

Signs of the disease can be considered based on the following syndromes:

• infectious-toxic;
• respiratory;
• gastrointestinal.

The disease, as a rule, begins quite acutely - the patient suffers from:

• severe chills;
• nasal secretions;
• sore throat;
• pain in the muscles;
• migraine.

There may be a disorder of the stool (it becomes watery). The patient often vomits. From the initial days, temperatures rise to 38 degrees and above. After a couple of days, a respiratory syndrome is possible. Of the complications, there is a danger of primary pneumonia (which is characterized by a cough with clear sputum, blood impurities and shortness of breath). The listening doctor, for sure, will hear the presence of moist rales and excessive hardness of breathing.

Chest x-ray shows inflammatory infiltrates, which are particularly extensive, rapidly merging and spreading beyond the boundaries of the initial inflamed focus. The formation of equity seals is possible.

If you do not treat the disease, start therapy late, or choose an inappropriate treatment course, dangerous complications will develop, such as:

• distress syndrome;
• respiratory failure;
• inflammatory processes in the lung tissues.

The end result can be deadly.

Bird flu is dangerous even for humans

Complications of the disease

One of the main symptoms of the development of the bird flu virus is distress syndrome. A blood test of a sick person shows a reduced number of leukocytes, as well as platelets with lymphocytes.

In addition, this disease can be expressed in a violation of the normal functioning of some internal organs (especially the kidneys and liver suffer). About a third of all patients experience kidney failure. Blood tests show elevated creatinine.

The described disease manifests itself in a person quite hard - especially if it concerns young children who have not yet reached the age of three. The danger of overcoming the blood-brain barrier with the subsequent development of encephalitis is likely. All this is accompanied by a severe migraine, vomiting, and sometimes consciousness is disturbed.

The treatment prognosis is quite unfavorable: in 60 percent of cases, a fatal outcome is likely (moreover, already in the second week of the disease).

Moreover, complications can not be avoided if:

• appeal for medical care will be untimely;
• immunodeficiency is observed (leukocyte counts are too low);
• have comorbidities.

That is why treatment should be started immediately after the first symptoms appear. And since only a qualified doctor can make an accurate diagnosis, do not hesitate to contact him.

When it was possible to transfer the infection, a person acquires immunity, which has a short-term character. That is, next season there is every chance of getting infected again.

All this also indicates the need to prevent such a disease in humans. Usually outbreaks of influenza infection among birds in one place or another are recorded, after which all necessary measures are taken to ensure that the infection does not spread to people.

Symptoms to watch out for

Here are the first signs of this disease in adults, observing which, you should worry and consult a doctor:

• fever, cough, difficulty breathing;
• upset stool (although there is no bloody discharge in the feces);
• the symptoms of an influenza infection quickly become more and more severe.

But to find out the exact diagnosis and confirm the presence of the disease will finally be possible only due to:

• immunological technique;
• molecular genetic technique;
• virological technique.

And only after realizing that it is, in fact, H5N1, it is necessary to find out how to treat it.

Rising temperatures should be alarming

Can you eat an infected bird?

Is it possible to eat poultry meat without fear of getting sick with bird flu? Yes. If the meat is cooked in the right way, it can be eaten. At temperatures exceeding 70 degrees Celsius, the infection dies.

However, infection is possible during the preparation of an infected individual, which will have to be plucked and gutted. In addition, viral agents can be found in bird faeces and secretions. The infection is also transmitted by airborne droplets - a person simply inhales its smallest particles that have risen into the air or landed on some surfaces.

Healing process

Treatment of the described disease in humans involves:

• carrying out regime measures - hospitalization and discharge only in cases where the temperature returns to normal (with adequate therapy and the absence of complications, this should be within a week);
• the use of antiviral drugs that are multifunctional (like Tamiflu or Relenza);
• the use of medical devices for symptomatic treatment (if the temperature rises above 38.5 degrees, it can be knocked down with antipyretics - Paracetamol or Ibuprofen). These same drugs enhance the effectiveness of antiviral therapy.

However, there are certain medications that are not used when treating H5N1. In particular, you should refrain from Aspirin and anti-grippins.

As for antibiotics, they are usually prescribed when diagnosing mixed pneumonia (which is not only viral, but also bacterial in nature).

When the inflammatory process in the lungs becomes severe, the doctor prescribes hormonal medication.

If we talk about emergency prophylactic agents, the use of Cycloferon, Amiksin, as well as other interferon inducers, will help. These drugs are recommended to be taken at initial suspicions of an illness: all the more, they are useful for those who belong to the risk group and everyone who, on duty, is in contact with an infected bird.

Prevention

By knowing how bird flu is transmitted, this infection can be avoided. That is why the issue of prevention is so important.

Perhaps the most effective preventive method remains vaccination. It is especially shown:

• those who are in contact with poultry and work on poultry farms;
• healthcare workers who come into contact with people infected with H5N

As a rule, standard vaccines are used - they have not yet come up with a specific vaccination directly from the specified ailment.

For chemoprophylaxis, interferon inducers are prescribed: for example, Tamiflu is excellent.

Most of all, doctors fear the further mutation of the virus so that it does not become transmitted between people. If this happens, the likelihood of a severe pandemic is high.

Separately, measures are taken to prevent this disease in birds. In particular:

• poultry is vaccinated (although this method cannot be called one hundred percent protection);
• young animals, as well as new individuals, are quarantined;
• closed pens are created so that poultry does not come into contact with wild birds;
• strict control of personnel working on poultry farms is carried out;
• careful control over the absence of dogs and cats on the territory of the farm is carried out.

Vaccinating birds helps prevent infection

By avoiding the development of influenza infection among chickens and other birds, a person will save his own health. This disease is very dangerous for the human body, and therefore it is necessary to start its treatment already when the first symptoms appear. But you should not make a diagnosis yourself, otherwise you risk making a mistake and treating the wrong thing at all.

Serious flu epidemics recur every decade. But the pandemic that happened in 1997 was atypical and dangerous. The new virus killed 60% of sick patients who were diagnosed with bird flu. In this article, we will talk about how this disease manifests itself. Let's talk about its origin, symptoms and treatment of the disease. We will also discuss measures to prevent influenza transmitted to humans from birds.

How did the new virus appear?

The influenza virus has been circulating in the animal environment since time immemorial. Cases of mass mortality of livestock and birds that had symptoms of SARS are described in chronicles. Reported deaths poultry were in the 20th century. But the flu, as a rule, never crossed the species barrier.

In 1997, the fears of many scientists were justified, who argued that the variability of the influenza virus was deadly. For the first time, cases of illness were reported in people who provoked the “chicken” virus. The infection has been found in individuals who have been in contact with sick birds infected with HPAI (highly pathogenic avian influenza). After that, patients developed severe symptoms, complications developed rapidly, and death occurred in 50% of cases.

After that, scientists closely followed the migration of this strain from China. But it was almost impossible to localize the infection. The fact is that the natural reservoir for bird flu is waterfowl. She carries the infection in the form of a mild cold. After migration, it can infect chickens, ducks and geese in backyards. This is how the virus spreads.

Geography of distribution

Highly pathogenic avian influenza has been circulating in China's poultry population. Further, in 2013, the virus spreads to Europe and Africa. Bird flu in Russia appeared after the first outbreak in China. Livestock of wild ducks and geese were seriously affected. Later, the swans died from the disease. The pandemic has spread to poultry. Chickens, turkeys, and ducks were slaughtered as a preventive measure to somehow contain the spread of the disease.

Avian influenza in humans can be caused by the H5N1 and H7N9 strains. Infection of humans with H7N7 and H9N2 is also possible. But they did not have such a severe clinical picture.

Clinical picture of the disease

Signs of bird flu depend on the strain of the disease that has entered the patient's body. They range from mild conjunctivitis to pulmonary edema with toxic shock. Therefore, any case of ARI reported after contact with birds should be examined by a physician.

The avian flu clinic in humans is slightly different from the classical course of the virus. Let's note the main differences.

1. The incubation period of the disease averages 2-3 days.
2. Bird flu symptoms develop very quickly.
3. The first clinic is high fever (39-40⁰) and cough. In contrast to the classic disease, avian influenza develops severe rhinitis.
4. Rapidly increasing symptoms of respiratory failure: shortness of breath, rapid breathing, shortness of breath.
5. Often associated with the defeat of the gastrointestinal tract: diarrhea, vomiting, abdominal pain.
6. High risk of developing complications.

How does infection occur?

Infected people had close contact with sick or dead birds. People who worked at poultry farms, kept a bird in their backyard got sick. Cases of infection have also been reported from butchering meat and removing faeces.

WHO recommends increased safety precautions when handling dead birds during mass deaths. It is recommended to remove carcasses in a protective suit and mask (preferably a respirator). For disposal use burial in the ground or incineration.

Employees of sanitary structures usually go to the epidemic focus, who carry out laboratory research and help dispose of the dead bird. In the event of such cases in home courtyards, it is recommended to immediately transfer information to the sanitary authorities.

Not reliably confirmed, but possible ways of transmitting infection through meat and eggs that have not undergone sufficient heat treatment. Some patients noted that they used such dishes. But it was not possible to confirm this with a laboratory method.

Person-to-person transmission has not been reported. But scientists do not exclude the possibility that the virus can mutate. In this case, the population of the planet is threatened by a deadly pandemic.

Treatment

If a bird flu virus is suspected, the patient is urgently hospitalized. Round-the-clock surveillance and isolation from society help to control the situation. Therefore, all cases of ARI occurring after contact with a bird should be consulted with a physician.

In the treatment of this type of influenza, modern antiviral therapy is used. Oseltamivir and zanamivir show good results. They are recommended to be administered within the first 48 hours after the onset of the first symptoms. But with severe complications of bird flu, these drugs also cannot be ruled out.

Bird flu is not sensitive to the old generation of antiviral drugs - adamantanes.

In addition, in the treatment of the disease, symptomatic agents are used - antipyretic, expectorant, vasoconstrictor.

In the event of severe complications, the patient is transferred to the intensive care unit. Treatment experience shows that even with pulmonary edema and a strong inflammatory process, it is not recommended to administer steroid hormones. They worsen the condition of patients.

Bird flu still has a high mortality rate (about 60%).

Preventive actions

In 2009, a vaccine against avian influenza (H5N1) was developed. As you know, vaccination of the population is the most effective way to combat epidemic diseases. Later, a vaccine was developed against the H7N9 strain. Both drugs entered the industrial production.

Persons in contact with poultry (employees of poultry farms, cutting shops) are subject to vaccination. There is also a need to administer doses of the drug to medical workers in foci of infection. It is the caregivers of sick people who can become the source of a new flu mutation that will be transmitted from person to person.

Made by Alena Ivanyuk

Bird flu (influenza)(Grippus (influenzae) avium, classic bird plague, European bird plague) is a highly contagious, acute disease characterized by septicemia, respiratory and digestive disorders.

History reference. For the first time, a disease called "exudative typhus of chickens" was described in 1880 in Italy by Perroncito. From Italy, the disease was repeatedly brought to various European countries and recorded under various names, including European, or classical, bird plague. In 1924 - 1925 pp. fowl plague has become widespread in the United States, for many decades it has been recorded in South America, North Africa, Palestine, Egypt, Japan, Korea, Israel, Australia, India, the Philippines, Ceylon. The viral nature of the disease was identified by Chentanni and Savunoci as early as 1901, and in 1956 Schaeffer and Waterson established the identity of the classical bird plague virus and type A influenza virus. A new unified classification was adopted for all pathogens of influenza in animals and humans based on the structure of hemagglutinin and neuranimidase, without taking into account the natural host from which the virus was isolated.

Now bird flu in the form of a class plague is rarely recorded, more often this infection is caused by serovars of virus A with low pathogenicity than the original influenza A virus. due to quarantine, which completely disrupted the economic life of the economy. During the epidemic of bird 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, M. I. Gorban.

The causative agent of the disease- RNA genomic virus from the Orthomyxo-viridae family, influenza A virus genus, subtypes A5 and A7. It has a spherical or filamentous shape, size 80 - 120 nm, it multiplies well in chicken embryos, primary cell cultures of chicken embryo fibroblasts. Agglutinate erythrocytes of chickens, rabbits, guinea pigs and, unlike the Newcastle disease virus, agglutinate also erythrocytes of sheep and horses. In the body of sick and recovered chickens, it causes the formation of hemagglutination, virus-neutralizing and complementary antibodies. On the basis of surface antigens (hemagglutinin H and neuraminidase N), viruses of the genus A are divided into 13 antigenic subtypes. Diseases in the form of classical fowl plague are caused by only two subtypes of avian influenza virus - A5 and A7. Other antigenic subtypes are much less pathogenic for chickens and cause only the respiratory form of the disease in young birds. In ducks, influenza virus subtypes A1, A2, A3, A4, and A6 cause the disease.

Influenza A virus is unstable in the environment, 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 hemagglutinuval activity of the virus at - 60 ° C persists for up to 2 years, at + 4 ° C - for several weeks.

Epizootology of the disease. Influenza A virus infects chickens and ducks of all ages, as well as 15 other bird species, including turkeys, guinea fowls, pheasants, geese, rooks, jackdaws, and sparrows. The source of the infectious agent is sick chickens and chickens that excrete the virus during external environment with eggs and all secrets and excretions, as well as ill virus-carrying birds within 2 months. Factors of transmission of the virus can be premises, litter, nests, paddocks, various care items, as well as corpses, carcasses of slaughtered birds, untreated slaughter waste, eggs, fluff and feathers of a sick bird, contaminated with the secretions of an infected bird. 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 birds occurs by airborne droplets, as well as orally through contamination of the pathogen with water and feed.

In the case of the primary occurrence in the farm, influenza passes among chickens in the form of an epizootic, which for 30 - 40 days covers almost the entire susceptible poultry population, with a high mortality rate, which is 80 - 100%. With the constant introduction of a new susceptible flock of chickens into the herd, systematic outbreaks of infection occur, the formation of a stationary department. In farms that are unfavorable for influenza, chickens and chickens often get sick with 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 a violation of hemodynamics, predetermines exudative phenomena and hemorrhagic diathesis. Hypoplasia of lymphoid organs, lymphocytes-singing and a sharp inhibition of the body's defense mechanisms cause a generalized form of infection and 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, depending on the antigenic subtype of the virus causing the disease and its virulence. Influenza of chickens, caused by the virus subtypes A7 and A5, is acute and manifests itself in a septic form characteristic of the classical (European) plague. There is an increase in body temperature up to 44 ° C, refusal to feed, depression, loss of sensitivity, cyanosis of the mucous membranes, comb and earrings, paresis and paralysis. A sick bird sits, ruffled, rests its beak on the floor, its wings are lowered, its gait is unsteady. Before death, body temperature drops to 30 ° C. Some sick chickens may show symptoms of damage to the nervous system or digestive tract, swelling of the subcutaneous tissue in the head and neck. Mortality is 70 - 100%.

In the case of chickens with influenza caused by the A1 subtype virus, 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 the poultry. There is an increase in body temperature up to 44 ° C, sneezing, shortness of breath, wheezing, shortness of breath, cyanosis of the comb, earrings, conjunctivitis, lacrimation. A sick bird loses its appetite, its feathers are protruding, its head and wings are lowered, and mucus flows from its beak. Mortality is 70 - 90%. Some birds show ataxia, tremors, and other signs of damage to the nervous system. In an adult bird, there is a decrease or cessation of egg production, which can occur even in the absence of symptoms of respiratory damage. For the respiratory form of the disease, mortality does not exceed 20%.

Influenza virus subtype A6 causes an epizootic among adult birds with a predominant lesion of the digestive tract. With the enteritic form, there is a refusal to feed, a decrease in egg production; the bird becomes inactive, lethargic, feathers are ruffled. Thirst, diarrhea, stools are foamy, have a greenish-yellow color, sometimes with an admixture of blood. With this form of the disease, there is a high incidence, but mortality does not exceed 5 - 15%.

pathological changes. Depend on the biological properties of the subtype of the virus, which leads to the death of the bird. With influenza A5, phenomena of hemorrhagic diathesis, swelling of the subcutaneous tissue in the head, neck, and dewlap are observed. In all cavities of the body and the heart shirt, accumulation of a significant amount of cloudy exudate is found. The muscles are cyanotic, with speckles and striped hemorrhages. Hemorrhagic enteritis and peritonitis, hemorrhages in the stroma of the follicles are also determined.

Influenza A7 causes hemorrhages in the serous integument, parenchymal organs, skeletal muscles, gastrointestinal tract. Characterized by necrotic lesions of the spleen, liver, kidneys. The membranes of the brain are hyperemic, edematous, under the dura there are diffuse hemorrhages, sometimes foci of necrosis.

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

Influenza virus A6 causes gastroenteritis, hemorrhages in the gastrointestinal tract, peritonitis, deep ulcers in the small intestine, mainly in the duodenum. Under the cuticle of the muscular stomach, striped hemorrhages are revealed, the cuticle is removed very difficult. 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 epizootological data, clinical signs of the disease, pathological changes and laboratory results.

Laboratory diagnostics. It includes virological studies of pathological material taken in the acute stage of the disease, a bioassay on chickens, as well as the study of paired blood sera with an interval of 5 to 7 days. For retrospective diagnosis, serological studies of the blood sera of a sick bird are carried out. Swabs from the nasopharynx and cloaca are sent to the laboratory for a proliferative diagnosis; after death - whole corpses or trachea, lungs, liver, brain, air sacs, intestines. Indication of the virus in the pathological material is carried out according to the GPA in an infected cell culture of chick embryo fibroblasts or RIF, RHA 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, Piga-sky or Bykovsky method, is carried out. In positive cases, cytoplasmic inclusion bodies of purple or bright red color are clearly detected 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, an immunofluorescence reaction is often used, with the help of which the viral antigen is found even if the pathogen cannot be isolated from the affected tissues. To isolate the influenza virus, 9–11-day-old chicken embryos are used, in which the pathological material is injected into the allantoic 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 an isolated influenza virus is carried out for 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 after 36 - 72 hours. Serological diagnosis of avian influenza is carried out for RTGA known viral antigens of avian influenza, as well as with local strains. The results of the studies are considered positive if the serum titer in the second sample, taken 10 days after the onset of the disease, is increased by at least 4 times.

Differential diagnosis. Provides for the 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 often observed, and there is almost never swelling of the subcutaneous tissue. In the large intestine, fibrinous layers and ulcers are found, which is typical only for this disease. The spleen and liver have no visible pathological changes. Hyperimmune serum against Newcastle disease virus agglutinates only erythrocytes treated with the homologous virus, and does not agglutinate erythrocytes sensitized by the avian influenza virus.

Infectious bronchitis is enzootic, mainly chickens get sick, mortality is low. Infectious laryngotracheitis differs from avian influenza by clearly expressed 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 virus of infectious bronchitis leads to a typical pathology of infected chicken embryos, and the virus of infectious laryngotracheitis - a vispo-like lesion of the chorion-alantoic membrane. Respiratory mycoplasmosis is differentiated using special serological reactions. Treatment has not been developed.

Immunity. After getting sick with the flu, it is not sterile. For specific prophylaxis, attenuated or inactivated vaccines are used against the subtype of avian influenza virus that causes the disease. For prophylactic vaccination against avian influenza A virus subtype H7 N1, which causes classical chicken plague, live vaccines from attenuated strains of Ru and P are used. The intensity of immunity must be controlled by RZGA on the 21st - 30th day after vaccination. If 80% of the studied vaccinated birds have antihemagglutinin titers not lower than 1: 10, immunity is considered sufficient for preventive disease prevention.

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 keeping and caring for birds. Particular attention should be paid to veterinary supervision when importing eggs for incubation and chickens only from farms that are free from contagious diseases, keeping them isolated, 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 packaging and the safety of imported feed.

When installing bird flu, it is advisable to slaughter the entire disadvantaged group. The carcasses of a sick and suspected bird, as well as the corpses of a dead bird, are burned. Conditionally healthy poultry is slaughtered for meat, carcasses are boiled at 100 ° C for 30 minutes and sold only in this farm. Feathers and fluff obtained from the slaughter of a conditionally healthy bird are dried in dryers at a temperature of 85 - 90 ° C for 15 minutes. If there is no drying unit, down and feathers are disinfected in any suitable containers with 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, sat down), leftover feed and manure are burned, and all poultry houses and the area around them are disinfected.

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

In the rehabilitated farm, substandard and unproductive poultry are systematically culled. Aerosol disinfection of premises is carried out in the presence of poultry using fine aerosols of lactic acid or chlorine turpentine. Eggs for incubation are imported from farms that are unfavorable for influenza. Each batch of young animals taken out is grown in a room completely freed from the previous bird, cleaned and disinfected, located in a safe poultry house. Upon reaching 45 days of age, chickens are vaccinated with an inactivated vaccine.

Influenza is a whole group of viral diseases. It is divided into three types: A, B and C. The first includes those that affect both people and animals. Respiratory and digestive organs are affected. The same goes for bird flu.

Viruses of the second type are dangerous only for humans, and the third - for humans and partly pigs.

It was first discovered in China, in Hong Kong. This happened in 1997. The disease then spread to Asia, and from there to Europe and Africa. It is carried mostly with wild migratory birds. They themselves do not get sick at all or carry the flu in a mild form, but can infect poultry and, less often, people.

Bird flu in Russia

Mostly the occurrence of the disease was noted in wild birds. But they were also sick at home, especially in the following areas:

• Novosibirsk;
• Chelyabinsk;
• Omsk;
• Kurgan;
• Tula;
• Tyumenskaya;
• as well as in Altai;
• and in Kalmykia.

The first cases were recorded in Siberia, in 2006. In humans, infection with avian influenza has not been recorded. However, there have been epidemics caused by swine and "human" subtypes.

As one of the preventive measures, a ban on the import of bird carcasses from those countries where outbreaks of this disease have been noted is used. Infected birds are also checked and destroyed.

Bird flu Moscow region

Cases of infection with this virus are also noted near Moscow. In particular, the disease was found in the poultry farms of Shchelkovsky and Sergiev Posadsky, as well as in private farmsteads of the Mozhaisk and Orekhovo-Zuevsky districts. Infected birds were destroyed. Many poultry farms have been quarantined.

Characteristics of the disease

Let's talk about it in more detail.

Officially, the flu is called Influenza virus A. It belongs to the Orthomyxoviridae family.

There are various subtypes that differ in the structural features of hemagglutinin (which is denoted by the Latin letter H) and neuraminidase (Latin N). The most common strain (subtype) of avian influenza is designated A/H5N1.

The disease is quite dangerous. According to official figures, more than half of the patients died (more precisely, 60%). However, it is likely that not all patients went to the doctor. In this case, the probability of dying is less, but still remains quite serious.

Infection

The virus is transmitted from one bird to another with direct contact. Domestic animals can become infected both from wild ones and from other, already infected, domestic ones. Dead birds are also contagious.

It is also possible to become infected through:

• water;
• feed;
• litter;
• eggs;
• poultry meat;
• rodents visiting the chicken coop.

The period from the entry of the virus into the body before the onset of the disease is from 2 to 5 days. This period depends on the state of health, age and the specific strain.

First signs and symptoms

Symptoms are the same as other types of flu:

• loss of appetite;
• sneezing
• lacrimation;
• disturbances and disheveled plumage;
• decrease in the number of eggs laid;
• they have;
• respiratory failure;
• blue and swelling of the ridge;
• uncoordination of movements;
• diarrhea.

Photo symptoms in birds:

In humans, bird flu manifests itself:

• cough and sore throat;
• rise in temperature;
• pain in muscles and joints;
• etc.

Pneumonia or other complications often develop. This is due to the fact that human immunity is not ready to deal with such varieties. Therefore, as a rule, the disease is more complicated than with traditional human types.

How to treat and can it be cured at all?

Unfortunately, there is no cure for sick birds. All sick chickens, as well as those who were in contact with them, are destroyed.

Quarantine is the primary means of preventing bird flu in chickens. That is why during outbreaks of influenza in other countries, the import of chicken from them is prohibited.

Effective method there is no cure. That's why it's important to stick to the rules.

• observe quarantine if a disease is reported in the region;
• do not buy chickens and eggs from dubious sources;
• avoid contact with wild birds, especially waterfowl.

Prevention

To prevent infection, it is important:

• Thoroughly wash knives, boards, etc. for cutting meat with detergents.
• Make sure that raw meat does not come into contact with other food.
• Cooking (not eating them raw).
• Do not touch fluff, feathers, carcasses of infected chickens.
• Wash hands and cutting tools after contact with raw meat.

Memo to the population

Regional veterinary services, as well as the Rosselkhoznadzor, issue leaflets. They contain information:

• about the bird flu virus;
• symptoms of the disease;
• distribution centers;
• preventive measures;
• and other useful information.

What other preventive steps need to be taken?

It is also important to do the following:

• Keep chickens clean, clean regularly and.
• Limit space.
• When buying a bird, check veterinary certificates.

Position of Rosselkhoznadzor

This organization checks farms for bird flu. When it is detected, quarantine is declared, and the infected bird is destroyed.

Impact on a person

For humans, this disease is quite dangerous, since the body rarely encounters such strains. The disease often occurs with complications, in particular, the respiratory and cardiovascular systems.

People can get infected:

• upon contact with infected chickens;
• or their meat, eggs, feathers and down;
• when drinking contaminated water;
• upon contact with litter.

Under influence high temperature(up to 70 ° C) the virus dies. But we do not recommend eating meat and eggs that are reliably known to be obtained from birds infected with influenza.

Avian influenza is an acute zoonotic infectious disease with a predominantly fecal-oral mechanism of pathogen transmission. It is characterized by a pronounced febrile-intoxication syndrome, lung damage with the development of RDS and high mortality.

ICD code 10

J10. Influenza caused by an identified virus.

Etiology (causes) of bird flu

The causative agent is influenza A virus of the genus Influenzavirus of the Orthomyxoviridae family. It is classified as an enveloped virus. The virion has an irregular or oval shape, covered with a lipid membrane pierced by glycoprotein spikes (spicules). They determine the hemagglutinating (H) or neuraminidase (N) activity of the virus and act as its main antigens. There are 15 known (according to some sources, 16) variants of hemagglutinin and 9 - neuraminidase. Their combination determines the presence of virus subtypes, and 256 combinations are theoretically possible. The modern "human" influenza virus has combinations of H1, H2, H3 and N1, N2 antigens. According to seroarchaeological studies, a severe pandemic of 1889-1890. was caused by the H2N2 subtype, a moderate epidemic of 1900–1903. - subtype H3N2, Spanish flu pandemic of 1918-1919. - H1N1 containing an additional protein derived from the avian influenza virus.

Epizootics of avian influenza in recent years are associated with subtypes H5N1, H5N2, H5N8, H5N9, H7N1, H7N3, H7N4, H7N7. Subtypes H1, H2, H3, N2, N4 circulate in wild bird populations; similar to the human influenza A virus. Under the lipid membrane is a layer of the matrix protein M-protein.

The nucleocapsid, located under the two-layer shell, is organized according to the type of helical symmetry. The genome is represented by single-stranded RNA, consisting of eight separate segments. One of the segments encodes non-structural proteins NS1 and NS2, the rest encode virion proteins. The main ones are NP, which performs regulatory functions, M-protein, which plays an important role in the morphogenesis of the virus and protects its genome, and internal proteins - P1-transcriptase, P2-endonuclease and B3-replicase. Differences in the structural proteins of the avian influenza virus and human influenza represent an insurmountable species barrier that prevents the replication of the avian influenza virus in the human body.

Different subtypes of this virus have different virulence.

The most virulent subtype is H5N1, which last years acquired a number of unusual properties:

High pathogenicity for humans;
- the ability to directly infect people;
- the ability to cause hyperproduction of pro-inflammatory cytokines, accompanied by the development of acute RDS;
- the ability to cause multi-organ disorders, including damage to the brain, liver, kidneys and other organs;
- resistance to the antiviral drug rimantadine;
- resistance to interferon.

The avian influenza virus, in contrast to that of the human virus, is more stable in the environment. At a temperature of 36 ° C, it dies in three hours, 60 ° C - in 30 minutes, during heat treatment food products(boiling, frying) - instantly. Tolerates freezing well. In bird droppings, it survives up to three months, in water at a temperature of 22 ° C - four days, and at 0 ° C - more than a month. It remains active in carcasses of birds for up to a year. Inactivated by common disinfectants.

Epidemiology of avian influenza

The main reservoir of the virus in nature- migratory waterfowl belonging to to the Anseriformes(wild ducks and geese) and Charadriiformes (herons, plovers and terns). Wild ducks are of the greatest importance. Influenza viruses in Eurasia and America evolve independently, so migration between continents does not play a role in the spread of the virus, longitude flights are crucial. For Russia, the Central Asian-Indian and East Asian-Australian migration routes are important in this regard. They include routes to Siberia via Malaysia, Hong Kong and China, i.e. regions where there is an intensive formation of new variants of the virus. Less significant are the East-African-European and Western-Pacific routes.

In wild waterfowl, the virus does not cause clinically significant disease, although a large-scale severe influenza epizootopy has been described in Arctic terns. The replication of the virus in birds occurs mainly in the intestine and, accordingly, it is released into environment with faeces, to a lesser extent with saliva and respiratory material. 1 g of faeces contains enough virus to infect 1 million poultry.

The main mechanism of transmission of the virus in birds- fecal-oral.

Waterfowl (ducks) are able to transmit the virus transovarially and thus serve as its natural reservoir and spread along their migration routes. They are the main source of infection for poultry, which, on the contrary, suffer from severe forms of influenza, accompanied by their mass death (up to 90%). The most dangerous subtype is H5N1. Infection occurs in conditions of free keeping and the possibility of contact with their wild counterparts. This is especially true for the countries of Southeast Asia (China, Hong Kong, Thailand, Vietnam and other states). There, along with large poultry farms, there are many small peasant farms.

The avian influenza virus can infect mammals: seals, whales, minks, horses and, most importantly, pigs. Cases of penetration of the virus into the population of the latter were noted in 1970, 1976, 1996 and 2004. These animals can also be affected by the human influenza virus. Human susceptibility to such avian viruses is currently low. All cases of infection were recorded in those who had long and close contact with a sick bird. An experiment conducted in the UK on the introduction of various subtypes of the virus into the body of volunteers gave a negative result.

In Thailand, with a population of 60 million, 12 human cases were reliably identified during an epizootic that affected two million birds. In total, by 2007, about 300 episodes of "bird" flu in humans were registered. Two cases of infection from a sick person have been officially recorded.

These data suggest that circulating strains of avian influenza virus do not pose a serious threat to humans. Thus, it can be concluded that the interspecies barrier is strong enough.

Even isolated cases of infection of people from birds and from patients indicate that the insurmountability of the interspecies barrier is not absolute.
The actual number of cases of infection from poultry, and possibly from sick people, given the real situation in regions where epizootics are rampant, can be many times higher. During the H7N7 influenza epizootic in Holland, 77 people fell ill, one died. High antibody titers were found in persons in contact with patients, which also indicates the possibility of transmission of the virus from person to person, but with a loss of virulence.

Secondly, the mutagenic potential of the avian influenza virus, especially the H5N1 subtype, is very high.

Thirdly, pigs are susceptible to avian influenza and human influenza viruses, so it seems theoretically possible for the pathogens to occur in the animal's body. Under these conditions, their hybridization and the emergence of assortant viruses with high virulence characteristic of the avian influenza virus, and at the same time capable of being transmitted from person to person, can occur. Due to the massive spread of avian influenza, this probability has increased dramatically.

Cases of human infection with swine flu have also been described, but the simultaneous penetration of two viruses into the human body is still less likely.

Fourth, it has been proven by genetic methods that the Spanish flu pandemic of 1918-1919. was of bird origin.

Fifth, in modern conditions thanks to the processes of globalization, the presence fast views transport, the possibility of spreading the assortant virus increases dramatically. Thus, it is fair to conclude that the likelihood of a new variant of the influenza A virus and the emergence of a severe pandemic is very high.

Mathematical modeling methods show that in a city with a population of seven million (Hong Kong), the number of cases at the peak of the epidemic can reach 365 thousand people daily (for comparison, in Moscow during the flu pandemic in 1957, this number did not exceed 110 thousand people a day ). According to WHO experts, it is possible that the rapid culling of birds during the epizootic in Hong Kong in 1997 prevented an influenza pandemic. US experts predict that in the event of a pandemic in America, from 314 to 734 thousand people will need to be hospitalized, from 89 to 207 thousand will die.

The pathogenesis of avian influenza in humans

Currently, the mechanism of development of influenza caused by the H5N1 virus in humans is not well understood. It has been established that the place of its replication is not only epithelial cells of the respiratory tract, but also enterocytes. Taking into account general biological and immunopathological processes, it can be assumed that the pathogenesis of influenza A (H5N1) in humans will develop according to the same mechanisms.

Various hemagglutinins of avian influenza viruses differ in their ability to recognize and bind to the receptor, sialic acid, bound in the oligosaccharide of cell membranes with galactose. The hemagglutinins of human influenza viruses interact with the residues of this acid, combined by a 2,6 bond with galactose, and the hemagglutinin of avian influenza viruses recognizes it in a 2,3 bond with galactose residues. The type of terminal sialic acid bond and the conformational mobility of surface lectin oligosaccharides are the main elements of the interspecies barrier for avian and human influenza viruses. Human tracheal epithelial cell lectins include 2,6 linkage type lectins and do not contain 2,3 linkage type oligosaccharides characteristic of avian intestinal and respiratory epithelial cells. Changes in the biological properties of a highly pathogenic strain of the A virus (H5N1), the emergence of its ability to overcome the interspecies barrier, can lead to damage to various types of cells in humans with the development of more severe forms of the disease. In the clinical picture of such pathologies, along with the catarrhal syndrome, damage to the gastrointestinal tract develops.

Clinical picture (symptoms) of bird flu

The incubation period for influenza A (H5N1) is 2-3 days, with fluctuations from 1 to 7 days.

The main symptoms and dynamics of their development

The onset of the disease is acute. Symptoms of intoxication are expressed. Body temperature from the first hours of illness rises to 38 ° C, often reaching hyperpyretic values. The febrile period lengthens to 10-12 days, and in severe cases with a fatal outcome - until the last hours of the patient's life. Chills, muscle and joint pains are characteristic. At the height of the disease (2-3rd day), catarrhal syndrome joins, manifested by the development of bronchitis, bronchiolitis, laryngitis; there may be signs of rhinitis. Sore throat and "flaming" oropharyngitis are characteristic. During this period, most patients develop primary viral pneumonia. At the same time, shortness of breath, a wet cough with sputum, possibly with an admixture of blood, appear. Harsh breathing, wet rales of various sizes, crepitus are heard above the lungs.

On a chest radiograph in early dates determine nonspecific changes in the form of diffuse, multifocal or individual infiltrates, tending to rapidly spread and merge. In some cases, segmental or lobar compactions may be detected. It is characterized by a progressive course, an increase in shortness of breath and the development of RDS. Along with intoxication and catarrhal syndrome, a gastrointestinal tract lesion develops, manifested by repeated vomiting, secretory diarrhea and abdominal pain. Perhaps an increase in the liver, accompanied by an increase in the activity of serum transferases. A third of patients develop acute renal failure, creatininemia.

In most patients, signs of damage to the nervous system are determined, impaired consciousness, and the development of encephalitis are possible.

Leukopenia, lymphopenia, thrombocytopenia are recorded in the hemogram.

There may be variants of the course of the disease with fever, diarrhea and no signs of respiratory damage.

Complications of bird flu

The infection is dangerous by the development of viral pneumonia, damage to the kidneys, liver, blood-forming organs. It is these consequences that often lead to the death of patients. It has been established that the place of replication of the H5N1 influenza virus in humans (at least in those who died as a result of the disease) is not only the respiratory tract, but also the intestines.

Risk factors for severe influenza A (H5N1) in humans:

Age of the patient (in children five years of age and younger, the symptoms of the disease are not pronounced);
- the duration of the manifestation of the disease before hospitalization (delay from hospitalization);
- anatomical level of damage to the respiratory tract;
- degree of peripheral blood leukopenia;
- the presence of multiple organ dysfunction.

Mortality and causes of death

Mortality is 50-80%. Most often, patients die from complications in the second week of illness.

Diagnosis of bird flu

The correct diagnosis at an early stage is the starting point for organizing targeted treatment, timely anti-epidemic measures and determining the prognosis. However, in the way of diagnosing avian influenza, there are certain objective difficulties associated with the similarity of the clinical picture of this disease and other acute respiratory viral infections.

A preliminary diagnosis of influenza A (H5N1) can be made on the basis of the following data from the epidemiological history and clinical manifestations:

The presence of reports of outbreaks of influenza A (H5N1) among the population of birds and animals or cases of death of poultry in the region of residence of the patient;
- contact with a sick person who is confirmed to be infected with the influenza virus (H5N1), seven days before the first clinical signs appear;
- contact with a patient with acute respiratory infections of unclear etiology, including fatal ones, seven days before the first clinical signs appear;
- an indication of the patient to travel to a country or territory where there are reports of an unfavorable epidemiological and / or epizootic situation for influenza A (H5N1);
- the presence of an occupational risk of infection of the patient;
- high fever combined with shortness of breath, cough;
- diarrhea (in the absence of blood in the feces).

The final diagnosis can be made after laboratory confirmation.

Laboratory diagnostics is based on the methods of virological research, serological reactions, immunofluorescent analysis and PCR.

Differential Diagnosis

Given that influenza A (H5N1) causes symptoms of respiratory tract damage, it is necessary to carry out differential diagnosis with other acute respiratory viral infections: “traditional” influenza (A, B), severe acute respiratory syndrome, parainfluenza, respiratory syncytial, adenovirus and enterovirus infections, and also legionellosis and ornithosis.

Indications for consulting other specialists

With the development of ARF - consultation of a resuscitator.

Diagnosis example

J10. Influenza caused by the H5N1 virus, severe; complication - pneumonia, ODN.

Indications for hospitalization

The clinical picture of a respiratory infection in a patient who had contact with a sick bird.

Bird flu treatment

Mode. Diet

When the diagnosis of influenza A (H5N1) is confirmed, treatment is carried out in a boxed department of a hospital. During the entire acute period of the disease, bed rest must be observed. A complete diet rich in vitamins and containing sufficient fluids is recommended.

Medical therapy

Etiotropic therapy

Currently, oseltamivir (Tamiflu), an antiviral drug belonging to the class of neuraminidase inhibitors, is the most effective among etiotropic drugs. It is prescribed at a dose of 75 mg orally twice a day for seven days. It is possible to increase the dose to 300 mg. You can also use rimantadine (rimantadine, algirem).

Pathogenic agents

In pathogenetic therapy, the leading role belongs to detoxification. According to clinical indications, intravenous administration of crystalloid solutions is used to correct acid-base balance and electrolyte balance.

In severe clinical forms of the disease, glucocorticoids and aprotinins are indicated. With the development of ARDS, treatment is carried out in the intensive care unit with mandatory respiratory support, a surfactant is administered. Symptomatic therapy is carried out according to indications.

Convalescents are discharged from the hospital no earlier than seven days after the restoration of normal body temperature.

All contacts with influenza A (H5,N1) patients are shown medical observation for seven days, with body temperature measurement twice a day. With its increase, the appearance of a cough and difficulty breathing, you should immediately seek medical help.

Forecast

The prognosis of the disease is unfavorable. Mortality is 50-80% in the second week of illness.

Prevention measures

Specific

Global monitoring under the auspices of WHO allows you to quickly detect a dangerous virus and start mass production of a vaccine. Mass vaccination can be started in nine months. At present, it is important to carry out high-quality anti-epidemic measures aimed at reducing the spread of human influenza. In particular, it is necessary to increase the number of vaccinated, which will reduce the incidence rate, and possibly susceptibility to a new version of the virus. In some countries, a limited number of vaccines against antigenic variants of the virus are produced. According to forecasts, they are the most likely candidates for a new pandemic virus.

The main method of combating avian influenza is the complete extermination of the number of birds on infected farms, and those who come into contact with them and carry out their destruction must work in respirators and overalls. Great importance is attached to disinfection using quaternary ammonium compounds (acepur) that are non-toxic to humans. They are easily neutralized by soaps and other detergents. Carry out quarantine measures, prohibit the export of poultry and eggs from the affected regions. In the surrounding farms and poultry farms, vaccination is carried out, but its effectiveness and expediency are doubtful. The presence of antibodies in vaccinated birds makes monitoring difficult, as it does not allow differentiation from infection, and there is also evidence that vaccination contributes to virus mutation.

In Russia, the introduction of infection is possible with migratory birds. However, the conditions for Agriculture in Russia (mainly closed poultry keeping, low probability of contact with pigs, less close contact between people and animals than in Southeast Asia) make it possible to practically exclude the possibility of the emergence of an assortant virus. In this regard, the main activities should be aimed at preventing the transfer of the virus from countries where it may appear. For this, it is necessary to tighten sanitary control at the border, recommend wearing respiratory masks, their preventive effectiveness reaches 98%.