Infection occurs through sick and ill individuals. All types of chickens, pigeons, turkeys, pheasants are susceptible to the disease. Chickens are more often infected with the virus.

A sick bird carries the virus for up to 2 years. The spread of laryngotracheitis occurs due to poor conditions for keeping birds: poor ventilation, crowding, dampness, inadequate diet.

What is chicken infectious laryngotracheitis?

For the first time, laryngotracheitis was registered in 1924 in the United States. American researchers May and Titsler described it in 1925 and called it laryngotracheitis.

The disease was later described as infectious bronchitis. After the 1930s, laryngotracheitis and infectious bronchitis were recognized as separate diseases.

In 1931, the disease of the larynx and trachea was proposed to be called infectious laryngotracheitis.

This proposal was made at the Committee on Bird Diseases. By that time, the disease had spread everywhere, including in the USSR.

In our country, infectious laryngotracheitis was first described in 1932 by R.T. Botakov. Then he called the disease infectious bronchitis. A few years later, other scientists described the disease with its modern name.

Today, chickens in many regions of Russia are infected with laryngotracheitis, causing enormous damage to personal and farm households. Birds die, their egg production decreases, weight gain. Poultry farmers have to spend a lot of money on stopping the infection and acquiring young animals.

Causative agents of the disease

The causative agent of laryngotracheitis is a virus of the family Herpesviridae having a spherical shape.

Its diameter is 87-97 nm. This virus can hardly be called persistent.

For example, if there are no chickens in the house, he dies after 5-9 days.

The virus persists in drinking water for no more than 1 day. Freezing and drying it is preserved, and under the influence of sunlight, the virus dies in 7 hours.

Kerazole alkali solutions neutralize the virus in 20 seconds. On the eggshell, it can be stored for up to 96 hours. Without sanitation, it penetrates the egg and remains virulent for up to 14 days.

Up to 19 months, the herpes virus remains active in frozen carcasses and up to 154 days in grain feed and feathers. In the cold season, the virus lives in the open air for up to 80 days, indoors - up to 15 days.

Symptoms and forms of the disease

The main sources of the virus are sick and ill birds.

The latter do not get sick after the cure, but 2 years after the illness are dangerous, since they release the virus into the external environment.

Infection occurs through infected air.

Also, the disease spreads with slaughter products, feed, containers, feathers and down.

In this case, the infection of the entire livestock occurs as soon as possible. More often the disease spreads in summer and autumn..

The course and symptoms of laryngotracheitis in chickens depend on the form of the disease, the clinical picture, and the conditions in which the birds are kept.

The incubation period for laryngotracheitis is from 2 days to 1 month. Let us consider in more detail the main signs of the disease in each of the three forms.

Hyperacute

Often occurs where the disease has not previously manifested itself. When a highly virulent infection enters the environment up to 80% of chickens can become infected in 2 days.

After infection, the birds begin to breathe with difficulty, greedily swallow air, stretching the body and head.

Some chickens develop a severe cough, accompanied by bloody coughing up.

Due to the rolling suffocation, the chicken shakes its head violently, trying to improve its condition.

In the house where sick chickens are kept, tracheal secretions can be seen on the wall and floor. The birds themselves behave passively, more often they stand in solitude, with their eyes closed.

The course of hyperacute laryngotracheitis is accompanied by characteristic wheezing, which is especially audible at night.

If the poultry farmers do not take action, after a couple of days, the chicken diseases begin to die one after another. The mortality rate is high - over 50%.

Sharp

In the acute form, the disease does not begin as suddenly as in the previous form.

First, a few chickens fall ill, after a few days others. Sick bird does not eat, sits with closed eyes all the time.

The owners note lethargy and general depression.

If you listen to her breathing in the evening, you can hear spitting, whistling or wheezing sounds that are not typical for a healthy bird.

She has a blockage of the larynx, which leads to impaired breathing and breathing through the beak.

Palpating the larynx will cause her to cough violently. Inspection of the beak will allow you to see the hyperemia and swelling of the mucous membranes. White spots may be visible on the larynx - cheesy discharge.

Timely removal of these secretions can help save the lives of chickens. After 21-28 days of illness, the rest may die from asphyxia due to blockage of the trachea or larynx.

Chronic

This form of laryngotracheitis is often a continuation of the acute one. The disease progresses slowly, the characteristic symptoms appear before the death of the birds. Dies from 2 to 15% of birds... People can also infect a bird with this form due to unsuccessful vaccination.

Often there is a conjunctival form of laryngotracheitis, in which the eyes and nasal mucosa are affected in birds.

It is more common in young animals up to 40 days of age. With this form of the disease in chickens, the palpebral fissure is deformed, they develop photophobia, and they try to hide in a dark corner.

With a mild form, chickens recover, but they may also lose their eyesight.

Diagnostics

The disease is confirmed after autopsy and laboratory tests.

To conduct virological research, fresh corpses, exudate from the trachea of ​​dead birds, as well as sick birds are sent to specialists in the laboratory.

There the virus is isolated on chicken embryos and subsequent identification is carried out.

A bioassay is also used on susceptible chicks.

In the process of diagnosis, diseases such as Newcastle disease, respiratory mycoplasmosis, smallpox, infectious bronchitis are excluded.

Treatment

Once the disease is diagnosed, treatment must be taken.

There are no specific drugs for laryngotracheitis, but symptomatic treatment can help sick birds.

Antibiotics can be used to reduce virus activity and biomycin to reduce chicken mortality.

Also for the treatment of infectious laryngotracheitis in chickens, like other birds, veterinarians use streptomycin and trivit which are injected intramuscularly.

Prophylaxis

Disease can be prevented in a variety of ways. Firstly, it is necessary to periodically disinfect the premises in which the birds live.

Moreover, they should be there. For disinfection, mixtures of chlorine-turpentine preparations, aerosols containing lactic acid are recommended.

Secondly, vaccination can be used. In regions with frequent outbreaks of the disease, a live vaccine is injected into the body of birds through the nasal passages and infraorbital sinuses.

There is a fraction of the likelihood that under certain conditions these birds can become active carriers of the virus, so this measure is only targeted prevention.

The vaccine can be rubbed into the feathers of birds or inserted into drinking water.

There is a vaccine specially developed for chickens from the " VNIIBP". Usually chicks are vaccinated from 25 days of age, taking into account the epizootic situation.

If the farm is safe, aerosol vaccination is carried out. The vaccine is diluted according to the instructions and sprayed in the area where the birds live.

After this, a temporary deterioration in the condition of the birds is possible, which disappears after 10 days. The resulting immunity lasts for six months.

Another vaccination option is cloacal... With the help of special instruments, a virus is applied to the mucous membrane of the cloaca and rubbed for a while. After a few days, the procedure is repeated. After vaccination, the mucous membrane becomes inflamed, but after that persistent immunity is developed.

The farm in which laryngotracheitis is diagnosed is quarantined. It is not allowed to take out chickens, equipment, feed, eggs.

If the disease manifests itself in one poultry house, all chickens are sent to the slaughterhouse, after which the premises are disinfected and biothermal disinfected. In poultry farms, the entry and exit of people from the territory is allowed after thorough sanitization of shoes.

Thus, laryngotracheitis is a dangerous infectious disease of chickens, which every poultry farmer should know about. By recognizing the disease in time, it is possible to save the hens from suffering and premature death.

Infectious tracheitis (ILT) is a viral disease that mainly affects chickens. The virus is localized in the mucous membranes of the larynx, trachea, less often the conjunctiva of the eyes and nasal cavity. The disease was first described in 1925 in the United States, but there is reason to believe that ILT was encountered earlier.

Currently, infectious chicken laryngotracheitis occurs in many countries: England, Holland, France, Germany, Hungary, Poland, Yugoslavia, Canada, USA, Italy, Sweden, Spain, South Australia, New Zealand, Indonesia.

In Russia, outbreaks of the disease are periodically recorded in all regions, but mainly large poultry farms suffer from ILT.

Characteristics of the disease

Chickens, peacocks, pheasants and some species of ornamental birds are susceptible to the disease. ILT is more often manifested in young chickens aged from 60 to 100 days, in disadvantaged areas - from 20-30 days of age.

The virus can also infect humans. This happens to people who work with vaccine material for a long time or are forced to come into contact with highly aggressive strains (workers in biofactories and laboratories). With poultry products - meat, eggs, feathers - a person cannot become infected.

In chickens, the disease is transmitted "from beak to beak." A sick bird develops strong immunity, but remains a lifelong carrier of the virus and infects other chickens. The same applies to birds vaccinated with live ILT vaccines. When such individuals are introduced into an unvaccinated herd, outbreaks of disease occur.

The ILT virus is not transmitted through the egg, but it can remain on the shell. Eggs from sick chickens cannot be incubated, but can be eaten.

The virus is sensitive to disinfection, its resistance is low in the external environment - it can persist for several weeks on care items, staff clothes, feeders and drinkers, in droppings.

Symptoms of the disease

Most often, infectious laryngotracheitis manifests itself in the autumn and spring, when temperature fluctuations weaken the airways of chickens and general immunity. Factors such as high humidity and dustiness of the air, poor ventilation, and unbalanced feeding contribute to infection.

The incubation period is short and is 1-3 days. In an acute course, up to 80% of the livestock suddenly falls ill, and the mortality rate of chickens reaches 50-60%.

With subacute disease, the disease spreads through the flock within 7-10 days, covering up to 60% of the birds, and up to 20% can die. ILT often becomes chronic with a 1-2% waste.

Symptoms of the disease are always associated with damage to the respiratory tract:

• wheezing, coughing, wheezing;
• discharge from the eyes and nose;
• when the trachea is squeezed with fingers, a cough occurs;
• when examining the larynx, redness, swelling, punctate hemorrhages, accumulation of mucous or cheesy masses in the lumen of the larynx are visible.

Chickens are depressed, eat poorly, and cyanosis of the comb and earrings is noted. Usually the bird gets sick within 14-18 days.

Symptoms of laryngotracheitis are sometimes conjunctival. The eyes become inflamed, foamy and or mucous discharge is visible, the third eyelid crawls over the eyeball. After recovering from the disease, the bird goes blind due to damage to the cornea. This course of infection is observed in chickens at the age of 20-40 days and covers up to 50% of the livestock. At the same time, symptoms of respiratory tract damage are present in a small number of chickens - a few percent.

When a dead bird is opened, a characteristic sign is a strong reddening of the trachea, the mucous membrane is swollen, dark cherry color throughout, the lumen of the trachea is often clogged with a blood clot. The lungs and air sacs are slightly affected, unless bacinfection has joined the virus - colibacillosis, mycoplasmosis, etc.

The diagnosis is made on the basis of the isolation of the ILT virus from the pathological material. The disease must be differentiated from b. Newcastle, infectious bronchitis of chickens, respiratory mycoplasmosis, hemophilia, chronic pasteurellosis.

Treatment and prevention

It is useless to vaccinate in the event of an ILT outbreak; the introduction of an additional dose of the virus only aggravates the situation. When using this method, take into account that in the future, it will be necessary to regularly vaccinate the newly arriving livestock against ILT, since the virus will forever remain on the farm.

Treatment in itself is inappropriate, an economically justified way out of the situation would be the slaughter of the entire herd, disinfection and the introduction of a new livestock. If this is not possible, then they resort to methods of partial recovery: a clearly sick and emaciated bird is discarded, the rest is treated.

Therapy

Treatment of laryngotracheitis is nonspecific. Chickens are provided with good feeding, heating and ventilation. Further, drugs are used.

• To suppress concomitant bacterial infections, broad-spectrum antibiotics are drunk: enrofloxacin, norfloxacin, ciprofloxacin, tetracyclines. Furazolidone powder can be mixed into the feed at the rate of 8 g per 10 kg of feed.
• Apply a solution of gentamicin aerosol by spraying from a spray.
• To disinfect the poultry house in the presence of poultry, lactic acid or triethylene glycol iodine is sprayed with an aerosol generator.
• Disinfection can be done by sublimation of chlorine turpentine at the rate of 2 g of bleach and 0.2 g of turpentine per 1 cubic meter. room volume, exposure 15 minutes.
• Solutions of complex vitamins - "RexVital", "Chiktonik", "Aminivital", "Nitamin" and the like are drunk.
• The preparation "ASD-2" is added to a wet mash at a dose of 1 ml per 100 head.

Measures for the prevention of infectious laryngotracheitis are reduced to preventing the introduction of the virus into the farm and vaccination.

In prosperous areas, vaccinating chickens is strictly not recommended - this way you will bring the virus to the farm for many years.

In practice, it is necessary to vaccinate only in two cases:

• when importing vaccinated poultry from another farm;
• in case of an outbreak of infection and the subsequent partial recovery of the herd.

There are not so many vaccines against ILT. In a rural backyard, it is advisable to use live vaccines. The best vaccination method is to drip into the eye. The cloacal method is less effective, and drinking gives a large percentage of non-immune individuals.

The bird is immunized upon admission to the farm or at the age of 30-60 days. Chickens older than 60 days and adult chickens are vaccinated once, younger ones - twice with an interval between vaccinations of 20-30 days.

Vaccine overview

What you need to know about ILT vaccines in general? There are two types of these drugs.

1. Chicken embryo vaccines. Provide strong protection but can cause serious complications.
2. Cell culture vaccines. Post-vaccination reactions do not cause, but give lower protection.

Vaccines against ILT are in the lineup of all leading manufacturers. Here are some recommended formulations for laying hens and broilers. The minimum packing in a bottle for most companies is from 1000 doses.

• Embryo vaccine against infectious avian laryngotracheitis "Avivak ILT", Russia.
• Dry vaccine virus against infectious avian laryngotracheitis from the VNIIBP strain. "VNIVIP", Russia.
• Virus vaccine against infectious avian laryngotracheitis from the VNIIBP strain. "Pokrovsky plant of biological products".
• Nobilis ILT (Nobilis ILT). Live dry vaccine against infectious avian laryngotracheitis with solvent. Intervet, Netherlands.
• Avian vaccine against infectious laryngotracheitis AviPro ILT. Lohmann Animal Health, Germany.

conclusions

Infectious laryngotracheitis is a serious viral disease. Chickens of all ages are susceptible to it. The main route of infection is the delivery of infected or vaccinated poultry to the farm, therefore, special attention is paid to completing the herd.

If a disease occurs on the farm, the best way to fight is to slaughter all poultry, disinfect and bring in a new livestock. True, for such an extreme measure, it is necessary to clearly know the diagnosis - to isolate the virus in the laboratory, which is not always possible in a private courtyard. Therefore, the method of partial recovery of the herd is used - a weak bird is discarded, and the rest is treated.

The decision on further vaccination must also be made on the basis of the diagnosis made by the doctor - once having introduced the vaccine into the farm, you will have to bear the costs of vaccination for the entire further existence of the farm.

Laryngotracheitis is primarily an infectious disease, its action extends to the larynx - this is "laryngitis" and the trachea is "tracheitis". ILT often occurs as a complication of colds in birds - pharyngitis, rhinitis, sinusitis, laryngitis, tonsillitis. How to eliminate the disease in time ?!

INFECTIOUS LARINGOTRACHEITIS OF BIRDS(Laryngotracheitis infectiosa avium), a viral disease characterized by inflammation of the pharynx and trachea. The history of the disease was officially recorded for the first time in the United States in 1925. Perhaps the disease manifested itself earlier. Today, the infection occurs in chickens in European countries, Australia, and the United States. In the Russian Federation, chickens in large poultry farms suffer from laryngotracheitis.

Etiology

The causative agent of the infection is a virus of the Herpesviridae family. Virions 180-250 nm in size, spherical. The virus is well cultivated in chick embryos when infected on the chorionallantoic membrane, in chick embryo cell cultures. The serum of recovered chickens contains virus-neutralizing antibodies.

Distinguish between virulent and weakly virulent viral strains, between which there are no antigenic differences. Sunlight kills the virus after 7 hours; on the surface of the eggs, it is inactivated when t = 60 ° C in 2 minutes, remains in the trachea of ​​corpses at t = 4-10 ° C for 30-60 days, at t = 8 ° С, -10 ° С - more than 370 days, in a dried state under vacuum - up to 2 years. Disinfecting 1% alkali solution, 3% cresol solution destroys the virus in 30 seconds.

Features of the disease

ILT can affect various breeds of birds, including decorative species. Peacocks, pheasants are no exception. Young chickens, which are 60-100 days old, are more susceptible to the disease, however, if the birds live in unfavorable conditions, then earlier: from 20-30 days of age. This infection can also be transmitted to humans. Workers in biofactories and laboratories are especially at risk, as they have to work with vaccinations and strains of infection. Infection is excluded if a person works in a factory with farm products. For example, from eggs, poultry meat, feathers, a person does not become infected. In birds, ILT is transmitted "from beak to beak".

A bird that has already suffered this disease cannot become infected again. Since birds acquire immunity to the tracheitis virus. The virus does not manifest itself, but the bird is the carrier of this disease. Consequently, it is capable of attacking other birds. This phenomenon is also relevant for vaccinated chickens. Outbreaks of laryngotracheitis infection usually occur after the introduction of the vaccine into the herd.

An egg laid by a sick bird can be eaten, but not incubated. As already noted, the virus is not transmitted through the product. But it remains on the shell. The infection does not tolerate sanitation. But it remains active on clothes, droppings, drinkers, and feeders for several days. After a certain amount of time in open space, the virus loses its resistance.

Laryngotracheitis symptoms

The infection appears during the off-season, especially in the spring and fall. The activation of the virus is facilitated by a decrease in immunity due to a lack of vitamins to maintain it, poor diet, dust, high humidity, lack of ventilation. The first manifestations occur within 1-3 days. Further, the disease intensifies, while the birds begin to die. The disease can destroy up to 60% of the chicken population. And 80% of chickens get sick. After 10 days, the disease covers 60% of chickens, and another 20% die. Chronic disease affects 1-2% of the total poultry population.

Signs of the disease can manifest themselves in the respiratory organs, as well as in the conjunctiva of the eyes. Noticeable symptoms include: hoarseness, coughing, flow from the mucous membranes of the eyes, nose. If you press a little on the larynx, a cough appears, redness, swelling of the mucous passages is noticeable. Laryngeal hemorrhages, curdled clots are not excluded. The eyes turn red, there is discharge, the eyeball swells. If the livestock is from 20-40 days, then blindness appears in chickens. The virus can harm 50% of birds. They begin to eat poorly, their appetite disappears, the comb and earrings change color to blue. These symptoms can appear individually, or all together. Chickens are sick for 14-18 days. The airways are less affected than the larynx or trachea. Usually, after opening, redness of the swallowing passages, swelling and edema of the laryngeal mucosa are found. The color is dark red throughout the mucous line, there are blood clots. Often, the respiratory tract and lungs are less affected. However, if other infections have joined the ILT, then the disease manifests itself quite aggressively.

Catarrhal - hemorrhagic and fibrinous inflammation of the trachea, edema and desquamation of the mucous membranes with hemorrhages prevail.

To detect the virus, the contents of the trachea from sick chickens are used. The virus is identified in the neutralization reaction (PH). Differentially, Newcastle disease, infectious bronchitis, smallpox, and respiratory mycoplasmosis should be excluded.

Treatment and prevention

Vaccination during an exacerbation of the disease is impractical. Since this can aggravate the already unfavorable position of the birds. If there is a desire to vaccinate chickens, then you need to take into account that you will have to do this periodically. This is financially disadvantageous. The virus then remains on the farm. Therefore, it will be better if you get rid of this batch of chickens completely, thoroughly disinfect the premises and bring in a new batch. If this procedure is not possible, then only those birds that are most affected by the virus can be discarded. Treat the rest of the chickens.

Treatment of the infection is non-specific. An integrated approach is required to improve the health of the bird population. First, you need to provide a good rational diet and conditions: ventilation, airing, heating. Secondly, use medications while feeding. Antibiotics can be used: tetracyclines, enrofloxacin, norfloxacin, ciprofloxacin. Furazolidone powder is mixed into food at the rate of 8 g per 10 kg of feed. You can additionally treat the room with sprays by spraying lactic acid or iodotriethylene glycol. They are used in the presence of chickens. Disinfection can be done by sublimation of chlorine turpentine at the rate of 2 g of bleach and 0.2 g of turpentine per 1 cubic meter. room volume, exposure 15 minutes. They drink solutions of complex vitamins - "RexVital", "Chiktonik", "Aminivital", "Nitamin" and others. The preparation "ASD-2" is added to a wet mash at a dose of 1 ml per 100 head.

Preventive measures of ILT are aimed at preventing infection, suppressing the introduction of infection into production. In favorable conditions for keeping chickens, vaccination of healthy individuals is considered useless. Moreover, this method can infect and infect chickens. Therefore, vaccination is used only in two extreme cases: when vaccinated chickens arrive from other poultry farms, or in order to treat the herd left after the culling of sick chickens. There are not many effective ways to fight. The most effective method is eye instillation (topical treatment). Drinking with antibiotics and disinfecting with sprays gives a better treatment result. The vaccine is administered to chickens at the age of 30-60 days. Chickens who are vaccinated once from 2 months of age. Chickens - 2 times, with an interval of 1 month.

Laryngotracheitis is a very serious type of bird disease that can kill more than half of the birds. The main source of infection is vaccinated chickens imported from other farms, or infected birds. An effective means of protection against this virus is the slaughter of the entire livestock, disinfection, and the introduction of a new batch. To exclude the slaughter of the entire herd by mistake, considering that the disease is caused by an infection of laryngotracheitis, it is necessary to conduct an analysis. However, this method is impractical to apply in the private sector. But, domestic chickens can also get sick. For private backyards, a partial recovery approach can be adopted by selecting chickens that are less exposed to infestation. Vaccination is carried out after the conclusion of an expert doctor. Having introduced the vaccine once, it will be necessary to regularly vaccinate the entire livestock during the period of the farm's existence. And bear the financial costs.

Economic costs include:

• drug and prevention costs;
• costs of veterinary services;
• loss of production associated with the loss of productivity of the poultry enterprise;
• death of young animals.

We hope this information and our advice will help you! Health to your chickens!

Infectious laryngotracheitis (ILT) is a viral disease of chickens, characterized by damage to the mucous membranes of the larynx, trachea, less often the nasal cavity and conjunctiva. The disease was first described in 1925, but there is reason to believe that ILT was encountered earlier.

Etiology. The causative agent of the disease is a virus from the genus Alphaherpesvirus (which also includes pseudorabies virus and herpes simplex virus), subfamily Alphaherpesvirinae, family Herpesviridae. Viral particles have an icosahedral nucleocapsid 94-100 nm in diameter, consisting of 162 capsomeres. The contour of the capsid is hexagonal with 5 capsomes on the verge. The virus has a supercapsid envelope about 10 nm thick. The size of viruses is from 270 to 340 nm.

The ILT virus is sensitive to physical and chemical factors. With direct exposure to sunlight, it lasts no more than 7 hours. Does not lose activity at a temperature of 4-10 ° C for up to 30 days, at 10 ~ 13 ° C for up to 10 days, at 30 ° C for 48 hours, at 37 ° C for up to 1 day, at 55 ° C for up to 10-15 minutes, at 60 ° С up to 3 minutes, at 75 ° С - 30 seconds. In a lyophilized state, in a refrigerator, the virus retains the ability to cause disease in chickens for 12 years. Indoors, in the autumn-winter period, it does not lose activity for 10-15 days, outdoors up to 80 days. In the carcasses of birds it is preserved until the beginning of their decomposition, in frozen carcasses at -10 - 28 ° C for up to 19 months. In tracheal mucus taken from sick birds at 37 ° C, the virus persists for up to 22 hours, at room temperature for 10 days, at 4 ° C for up to 30 days. In tracheal exudate diluted with 50% glycerol solution in phosphate buffer, at 37 ° C it does not lose activity for 7-14 days, at -4 ° C for up to 217 days. In the trachea from sick chickens, stored at -8 ..- 10 ° C, it remains virulent for up to 370 days, in the chorioallantoic membrane from infected embryos, at a temperature of 25 ° C - up to 5 hours. Freeze-dried vaccines of previous years, after 25 years of storage, were able to induce immunity to ILT in 40% of vaccinated birds. In 1% sodium hydroxide solution and in 3% creosol solution, the virus is inactivated within 30 seconds, in 5% phenol solution - in 1-2 minutes. In formaldehyde vapors - after 40 minutes. It is quickly inactivated in indoor air by a mixture of formalin and creolin in a ratio of 3: 1, at a dose of 15 ml per 1m 3. In a droplet and dust aerosol, at a temperature of 19-1 ° C and a relative humidity of 40-55%, the virus remains active for 1.5 hours. On artificially infected feathers of birds, on the surface of equipment, soil, in grain feed and water, the virus quickly loses its virulence. Retains viability and can cause damage to embryos and accumulate in the chorioallantoic membrane.

Serological differences in the existing strains of the infectious laryngotracheitis virus have not been established, but strains of different virulence sometimes have a different ability to be neutralized by hyperimmune sera. Different strains of the ILT virus usually differ in molecular structural features, storage resistance, thermal resistance, virulence for birds and chicken embryos, tropism, rate of excretion from cells in tissue culture, and avidity.

In the body of birds, the infectious laryngotracheitis virus causes the formation of virus-neutralizing and precipitating antibodies. Virus neutralizing antibodies are formed within 5-7 days after infection, reaching a maximum level on day 21, which then decreases slightly and remains at a certain level for several months. They come to light within a year or more. In the excretions of the tracheal mucosa, antibodies, as a factor of local immunity, can be detected as early as 7 days after infection and remain at a sufficiently high level from 1 to 38 days. The humoral immune response to infectious laryngotracheitis virus is not the main defense mechanism against infection. This is confirmed by a weak relationship between the titers of serum antibodies, as well as the presence and level of mucosal antibodies and the state of immunity in birds to the ILT virus. The leading factors of avian resistance to infectious laryngotracheitis are the local cell-mediated reaction in the trachea, as well as the cell-mediated immunity of the avian organism. Maternal antibodies to ILT virus, transovarially transmitted to chickens, do not provide complete protection against infection and do not interfere with the action of the vaccine. When vaccinating chickens younger than 2 weeks, the immunogenic effect of the vaccine is lower than that of adult chickens. At the same time, chickens can be successfully vaccinated even at 1 day of age. Chicks over 2 weeks of age are more responsive to vaccination and exposure to field virus, resulting in more stable immunity to challenge. Antiviral protection begins to form by 3-4 days after vaccination, and a complete immune response by 6-8 days. The decrease in immunity begins from 8-15 weeks after vaccination, but its noticeable decrease occurs after 15-10 weeks. This casts doubt on the need for re-vaccination when birds are short-lived. It is allowed that some strains of the infectious laryngotracheitis virus have natural hemagglutinating activity, but in most of them it appears after additional processing. The allantoic-amniotic fluid of chicken embryos infected with the ILT virus, after treatment with a solution of amorphous trypsin and incubation at a temperature of 37 ° C, is capable of causing agglutination of a 1% solution of chicken erythrocytes at a dilution from 1: 2 to 1: 16192. The control allantoic-amniotic fluid of uninfected embryos, processed according to the same technique, hemagglutinates 1% erythrocytes, diluted 1: 4, and the working solution of trypsin diluted 1: 8. In the blood serum of convalescents and vaccinated birds, antibodies begin to appear by 14 days after infection or, respectively, after vaccination and reach a maximum level by 35 days.

After infection with the infectious laryngotracheitis virus or vaccination of birds, antibodies in the blood serum begin to appear on 3-4 days, are transmitted transovarially and persist in chickens for 8-14 days. However, the presence of antibodies in embryos does not protect them from death, which, when infected with a pathogenic strain, can reach 80%. Chickens, starting from one day old, despite the presence of maternal antibodies, are susceptible to experimental infection with the ILT virus. The susceptibility to infection in chicks with passive antibodies increases from 7 days of age to 8 weeks of age.

The virus has a tropism for the epithelium of the larynx, trachea, eyelids, cloaca and bursa. The sensitivity to the virus of infectious laryngotracheitis of the mucous membrane of the cloaca and bursa is higher than that of the mucous membrane of the upper respiratory tract.

Epizootology. Mostly chickens are susceptible to the disease, as well as pheasants, peacocks and some species of ornamental birds. Under natural conditions, infectious laryngotracheitis in chickens is more often recorded from 20-30 days to 8-9 months of age. Chickens 5-6 months old and older, who have not been in contact with the ILT virus and are free of antibodies to this virus, are very susceptible to the disease. It is experimentally possible to infect chickens of any, even one day old. There are conflicting reports on the susceptibility of turkeys to ILT infection. There are no fundamental differences in the course of the disease in purebred and crossbred birds, but there is an opinion that chickens of common breeds are less susceptible to the disease. Domestic and wild ducks, geese, guinea fowls, parrots, canaries, sparrows, crows, pigeons, starlings, turtle doves are considered resistant to ILT infection. But there is also the opposite information, including in relation to ornamental birds.

A person is susceptible to infection with the ILT virus, especially during professional contact with material containing vaccine, and more, a pathogenic strain of the virus. The individual characteristics of the susceptibility of people to infection are noted. People who are in a room containing a bird suffering from an acute form of ILT or during aerosol vaccination of birds, as well as specialists who develop a vaccine strain of the ILT virus in production conditions, or control the quality of the vaccine with a control infection of birds with a highly pathogenic virus, become sick. With each subsequent contact, a small dose of the virus and a short stay in an infected environment are enough for the onset of the disease. Inflammation of the oral and nasal cavities, larynx, upper trachea and conjunctivitis develops. Some people develop pathology of the skin of the face (edema, hyperemia) and / or the hands. In rare cases, the infection is transmitted from a sick person to his family members. With increased susceptibility, nodules appear in the mucous membrane along the blood vessels, similar to small plaque nodules observed in the choriallantoic membrane of chick embryos infected with ILT. A similar pathology occurs subcutaneously in the area of ​​the hands. In some people, due to the production needs of those who are often in contact with the ILT virus, chronic bronchitis, characterized by periodic coughing, develops. Human infection occurs mainly by aerogenic means. People do not develop immunity to ILT. No cases of human infection from poultry products used for food (eggs, meat) have been recorded.

Infectious laryngotracheitis can occur at any time of the year, but it manifests itself better during periods of sharp climatic fluctuations.

The disease proceeds, as a rule, in the form of enzootics, the nature of which depends on the general condition of the birds, compliance with sanitary and hygienic standards, conditions of feeding and keeping. In dysfunctional farms for infectious laryngotracheitis, with seasonal rearing of young animals (in spring and summer), chickens get sick in summer and early autumn, chickens in late autumn, after transfer to broodstock. In adult chickens, with similar technological and epizootic features of the economy, there are no outbreaks of ILT, since they get sick at an early age and acquire resistance to re-infection.

Clinical signs. ILT in chickens is hyper-acute, acute, subacute and chronic. According to the form of manifestation, laryngotracheal, conjunctival and atypical forms of infection are distinguished.

A hyperacute (laryngotracheal) course is observed when a highly virulent virus enters a herd that was previously free from ILT. The disease occurs suddenly, in 1-2 days it covers up to 80% of the livestock. Birds breathe with difficulty, capturing air with their wide open beaks and continuously stretching their head and body. There is a frequent, spasmodic cough. Birds cough up exudates, sometimes bloody. Trying to get rid of suffocation, they shake their head. The accumulation of exudate in the area of ​​the nostrils and eyes is possible. With floor maintenance, the walls and floor, and with cell walls and floor, the cells are splattered with tracheal and other secretions. Birds are inactive, often stand with closed eyes, inhalation and exhalation are accompanied by characteristic wheezing or whistling sounds ("the bird has begun to sing"), which is especially well detected at night. There is a general depression, decrease or complete loss of appetite, cyanosis of the head. But since with the hyperacute form of ILT there is a short period of recovery, then by the time of death (2-3 days after the onset of the disease) the bird does not have time to "lose weight", and, as a rule, individuals with a higher live weight die first. The mortality rate is 50-60% and higher.

In the acute course, up to 60% (or more) of the population of an unsuccessful group of birds fall ill within 7-10 days, but the mortality rate does not exceed 20%. At the beginning, ILT signs appear in some individuals, and then most birds fall ill. There is a deterioration in appetite, lethargy, inactivity, wheezing or wheezing, croaking sounds when breathing. Light squeezing of the trachea with the fingers is accompanied by a painful reaction and a cough. During an intravital examination through an open beak, edema, hyperemia of the larynx are noted, sometimes the presence of punctate hemorrhages in it, and in prolonged cases, a congestion around the larynx, on the frenum of the tongue, on both sides of it, cheesy-fibrinous overlays in the form of easily removed from the mucous membrane of whitish-yellow spots of various sizes and shapes. The presence of such overlays sometimes causes bad breath in birds. The duration of the disease is 3-10 days or more. Clinical signs disappear in 14-18 days. Most birds with reduced resistance die from asphyxia due to a blockage of the trachea or larynx. Removing the curd plug from the larynx can prevent death. Recovered birds look outwardly healthy, but some of them have a cough, sneezing, signs of conjunctivitis. During the period of acute illness in laying hens, egg-laying decreases or stops. The course of the disease during the laying period, in combination with bad weather and a violation of the microclimate, can provoke partial or complete molt.

The subacute course of ILT is preceded by a slower progression of infection. Sometimes the subacute course is a continuation of the acute form of the disease. Clinical signs characteristic of affection of the larynx and trachea are most pronounced several days before the death of the birds. The mortality rate is 10-15%.

The chronic course is considered as a continuation of the disease in birds that have recovered from more intense forms of ILT, and can also occur in conditions of unsatisfactory vaccination of birds against ILT. It is characterized by a lag in the development of young animals, a decrease in egg production in adult birds. Cough and signs of suffocation are more noticeable when the birds are anxious and frightened. Discharge from the nostrils and eyes is also noted. The mortality rate is 1-2%.

The conjunctival form of ILT occurs in chickens, starting from 15-25, and more often from 30-40 days of age, with the simultaneous presence, only in some birds, of lesions of the larynx and trachea. It can also occur in young chickens in combination with the laryngotracheal form, or be a continuation of it. The conjunctival form begins with hyperemia of the mucous membrane of one or both eyes, edema of the eyelids, deformation of the palpebral fissure, which becomes elongated (almond-shaped), which is accompanied by exposure of the mucous membrane of the inner corner of the eye. Photophobia, lacrimation develops, serous exudate appears, sometimes foamy masses accumulate in the inner corner of the eye. The affected third eyelid increases in size and may obscure part of the eyeball. Chickens, afraid of the light, rush to darkened places and sit with their eyes closed. The mucous exudate sticks together the eyelids. Periorbital swelling, damage to one or both infraorbital sinuses, inflammation of the nasal mucosa are noted. Serous, in severe cases, mucopurulent rhinitis, occurring in more than 50% of birds with ILT. With a prolonged course of the disease, caseous masses accumulate under the third eyelid, which can fill the entire conjunctival sac and deform the affected eye area. Perhaps the development of keratitis, with ulceration of the cornea, involvement of the eyeball in the pathological process, with partial or complete loss of vision. With a mild course of conjunctivitis, especially not complicated by secondary microflora, the chickens recover. Birds that have lost their eyesight cannot find food and water, as a result of which they are quickly depleted. Mortality (death and culling) of birds with the conjunctival form of ILT can reach 80%.

The atypical (asymptomatic, subclinical) course of ILT is almost not accompanied by characteristic clinical signs of the disease. In isolated cases, signs of laryngotracheitis are recorded. Occurs in permanently dysfunctional farms, where there is a natural asymptomatic disease of chickens. The presence of disease can be indicated by a low (10-12) percentage of birds responding to ILT vaccination by the cloacal method and the absence of symptoms of disease in other birds, both before and after vaccination, during the remainder of the rearing period.

In natural pheasants, the incubation period is 6-10 days. Possibly acute, subacute, chronic and asymptomatic course of the disease. In the acute form, pheasants have difficulty breathing, with noises, a decrease in egg production by up to 50% is possible. The mortality rate sometimes reaches 50% and occurs from asphyxiation. The chronic course in natural situations may be asymptomatic. When pheasants are kept in captivity, the incubation period is 1-5 days. Pheasants suddenly lose their appetite, shortness of breath, cough, sneezing, serous conjunctivitis. Pheasant chicks undergoing ILT up to 2 weeks of age are subsequently accompanied by a delay in the development of the ovary and oviduct. Mortality rate up to 25%. Adult pheasants get sick with a decrease in egg production, laying eggs with watery contents and poor-quality shells.

Ornamental birds are susceptible to ILT. Deaths have been reported in canaries on several occasions. ILT is manifested by a deterioration in appetite, inactivity of birds, difficulty breathing with noises, sneezing, coughing, sinusitis, and often conjunctivitis. In the treatment of ornamental birds, antibacterial drugs are used to prevent complications from secondary microflora.

The ILT virus, like other herpes viruses. after the birds recover, it is in their body in a latent form. Both pathogenic and vaccine strains of the ILT virus can persist in the nervous tissue, including the trigeminal ganglia.

Pathomorphology. The laryngotracheal form is mainly characterized by damage to the larynx and trachea of ​​varying severity. In the case of a hyperacute course of the laryngotracheal form of ILT, the trachea is hemorrhagicly inflamed along its entire length, with the presence of plugs in the lumen, which are mucus mixed with blood or its clots. In an acute course, inflammation of the oral and nasal cavities, infraorbital sinuses, trachea is observed, punctate hemorrhages in the rectum are possible. In the subacute course of the laryngotracheal form, inflammation of the larynx and trachea. In case of complication by secondary microflora, the presence of cheesy diphtheria films or cheesy plugs of a dirty gray color with brown (due to blood) veins on the mucous membrane of the larynx and the upper part of the trachea. Venous congestion in the lungs is detected, sometimes inflammatory changes in the lungs and bronchi, occasionally in one or both bronchi there are plugs consisting of caseous exudate. In some cases, there is a catarrhal-hemorrhagic enteritis, cloacitis and bursitis. When the larynx or trachea is blocked by exudate and the subsequent death of birds from asphyxia, congestive hyperemia of the parenchymal organs, an increase in the volume of the heart, and minor hemorrhages on the epicardium are noted. For the pathomorphology of the conjunctival form and the atypical (asymptomatic, subclinical) course of ILT, see above.

During histological examination in the epithelium of the mucous membrane of the trachea and eyelids, in the first days of the disease (48 hours after infection and up to 6 days) by the period of epithelial necrosis, eosinophilic intranuclear inclusions are revealed.

Diagnostics. Retrospective serological diagnostics of ILT is carried out by examining blood serum in the RN, in the solid-phase ELISA method, less often in the RDP, RIGA and RGA.

To isolate the virus, tracheal exudate is used, scrapings from the affected mucous membrane of the larynx, trachea, eyelids, conjunctiva of birds taken at the onset of the disease (no later than 7 days). Patomaterial is suspended in saline in a ratio of 1: 5 or 1:10, centrifuged in a low-speed centrifuge at 3000 rpm. Antibiotics are added to the supernatant: penicillin 200 U / ml, streptomycin 100 μg / ml. After keeping for 12 hours at a temperature of 4-8 ° C and checking for the absence of bacterial growth, 7-9-day-old chicken embryos in a volume of 0.1 ml are used for infection at HAO. In 48 hours after infection, insignificant edema is revealed in the ectodermal layer of the CAO epithelium and proliferation foci are formed. The mesodermal layer of the CAO is edematous, thickened, with an accumulation of fibroblast-like cells. The endodermal epithelium is without specific changes, but slightly hypertrophied. Eosinophilic inclusions are found in the nuclei of the ecto- and endodermal epithelium. In the presence of the ILT virus, 60-72 hours after infection, macroscopic changes appear on the chorioallantoic membrane of the embryos, which persist up to 5 days after infection. By morphology, they are divided into two types: small-nodular, usually found on all surfaces of the chorioallantoic membrane, more often located along the blood vessels and focal, found only at the site of application of the virus. There is an increase in the amount of allantoic fluid by 1.5-3 times, as well as the accumulation of uric acid salts and fibrin flakes in it. In embryos that died after infection with the ILT virus, there is skin hyperemia in the back of the trunk and legs. When the embryos infected with the ILT virus, but remained alive, are opened on days 4-5, there are no changes on the skin, even in the presence of typical changes in the CAO. The ILT virus accumulates as much as possible in the CAO of the embryo, with a much lower concentration in the CAF.

When the embryos of 13-, 14- and 16-day-old turkeys are infected, changes similar to those found in chicken embryos develop, but they develop more slowly, and the death of embryos occurs on the 6-7th day. It is not possible to reproduce ILT in 64-day-old turkey poults with the virus accumulated on turkey embryos.

When infected with the ILT virus in guinea fowl embryos of 9-, 11-, 15-, or 18-day incubation, CAO lesions appear in 3-5 days. The peculiarity of the changes noted is that the foci of CAO lesions in guinea fowl embryos more vaguely and more imperceptibly pass into the healthy membrane tissue. The virus accumulated on guinea fowl embryos is apathogenic for 50-day-old guinea fowls.

When infected with ILT virus of 10-15-day-old duck embryos, after 4-8 days at the site of application of the virus, lesions of a rounded shape, vague, with a whitish shade, gelatinous consistency, 2-3 cm in diameter, are formed. Macroscopic lesions of the rest of the CAO are not observed. Sometimes CAJ can be with signs of opalescence and with the presence of small flakes.

The ILT virus is well cultivated in the culture of kidney cells of chicken embryos. The infectious titer of the virus accumulated on the fibroblasts of chicken embryos is somewhat lower. It is possible to cultivate the virus on a duck kidney cell culture. The virus does not accumulate on perivated SOC cells, but multiplies on HeLa, but without a cytopathic effect.

The cytopathic effect of the virus in the culture of fibroblast cells or kidney of chicken embryos begins 3-5 days after infection and is manifested by the rounding of the monolayer cells, the presence of multiple vacuoles in the cytoplasm, located mainly near the cell nucleus and giving the cytoplasm a granular appearance. Intranuclear inclusions characteristic of ILT are noted in the nuclei of fibroblasts.

Determination of the biological activity of the virus isolated in embryos or in cell culture is carried out by titration in embryos or in a chicken cell culture. Identification of the isolated agent is performed in PH, ELISA, MFA, RDP or electron microscopy.

For setting up a bioassay, it is better to use the source material prepared for the isolation of the virus on embryos or chicken cell culture. It is also advisable to check the virus isolate obtained in embryos or cell culture in a bioassay. The bioassay is carried out on two groups of chickens: 1 - from an ILT-safe farm, free from antibodies to this virus; 2 - immune to ILT virus. Chickens of both groups are infected with vaccinated material in a volume of 0.5-0.1 ml by rubbing into the mucous membrane of the cloaca and in the same amount applied to the slightly scarified mucous membrane of the larynx and trachea, and to exclude smallpox into the feather follicles of the leg. In the presence of ILT virus in the test material, non-immune chickens become ill after 3-5-10 days with clinical signs of ILT. In chickens infected only intra-cloacally for 3-5 days, inflammation of the mucous membrane of the cloaca is noted in the form of edema, redness and the presence of a small amount of serous-mucous exudate. Chicks that are immune to ILT stay healthy. The presence of smallpox virus in the test material is accompanied by an inflammatory reaction of the feather follicles of the lower leg, characteristic of smallpox. When chickens are infected with the introduction of the test material containing the ILT virus into the infraorbital sinus, edema, lacrimation, and exudate discharge from the nostrils develop.

For a cytological express diagnostic method, smears are prepared from scrapings of the epithelium of the mucous membrane of the trachea, larynx, the eye is fixed with absolute methyl alcohol for 3-5 minutes and stained in a solution of Giemsa paint (approximately 1 drop of paint per 1 ml of distilled water) for 2 hours, at a temperature of 37 ° C. They are washed with water, briefly treated with absolute methyl alcohol, thoroughly washed again with water, dried and, after applying a drop of emergent oil, viewed with increasing vol. 90, approx. 10. With high-quality staining, the cytoplasm of epithelial cells is pale blue, the membrane of the nucleus is dark blue (or blue). In the nucleus, light-red inclusions with an enlightenment rim along the periphery of the nucleus are visible in the immediate vicinity of the nuclear envelope. Histological express diagnostics of the material consists in staining the sections with hematoxylin and eosin, which makes it possible to identify pink intranuclear inclusions (eosinophilic). For these methods, material taken from the birds at the onset of the disease should be used. Electronic microscopic express diagnostics is carried out by examining scrapings from the mucous membrane of the trachea or its contents, taken at the initial stages of the disease and processed by the method of negative contrast.

Treatment and prevention. No drugs have yet been found to prevent an outbreak of ILT. Antibiotics, without having a detrimental effect on the ILT virus, can reduce the intensity of the disease. Biomycin at a dose of 10-30 thousand units a day or penicillin at a dose of 5-10 thousand units. and streptomycin at a dose of 10 thousand units. in a 0.5% solution of novocaine intramuscularly, daily for 2-3 days in a row, significantly reduce the mortality of birds. A similar effect can be obtained by feeding a dacha (wet mash) of Dorogov's stimulant (ASD F-2) at a dose of 1 to 5 mg per day for each bird. It is very important to introduce fat-soluble vitamins into the diet of birds, especially vitamin A and also E.

In the event of an ILT outbreak, it is advisable to disinfect the air in the presence of a bird, including with a mixture of chlorine-turpentine preparations, at the rate of 2.0 g of bleach containing at least 36-17% of active chlorine and 0.2 g of turpentine per 1 m3 of the room , exposure 15 minutes (for young animals, the dose and exposure are 2 times less). Fine aerosols of lactic acid (100 mg / m 3) and triethylene glycol (20 mg / m 3) can be used. To create an aerosol, special installations are used that supply compressed air at a pressure of 3-4 atm. and with a nozzle capacity of 20 ml / min.

Live attenuated vaccines are used for specific prevention of ILT. But vaccination can lead to the emergence of latently infected virus-carrying birds. It is recommended to carry it out only in regions that are unfavorable for ILT. Live virus vaccines are applied by injection into the nasal passages and infraorbital sinuses, instilled into the eye, rubbed into feather follicles or into the mucous membrane of the cloaca, aerosol and orally with drinking water. Vaccination with drinking water can detect a large percentage of birds with immature immunity to ILT. The success of vaccination with drinking water is ensured if the vaccine virus comes into contact with sensitive cells of the epithelium of the nasal cavity due to aspiration of the virus through the external nasal openings or choanae. But when drinking a vaccine, this phenomenon is not always observed.

The dry virus vaccine from the VNIIBP strain is harmless to chickens and is used to prevent ILT by aerosol, ocular, cloacal and enteral (with drinking water) methods. A clinically healthy bird is vaccinated from the age of 25 days, but the specific dates for the start of vaccination are chosen in accordance with the epizootic situation on the farm. It is desirable that vaccination occurs no later than 25 days before the expected manifestation of clinical signs of ILT. Vaccination is double, with an interval: with cloacal 30 days, with ocular and enteral 20-30 days, with aerosol 16-20 days. Chickens over 60 days old and adult birds are vaccinated once.

Aerosol vaccination is used only in farms free from respiratory diseases, especially infectious etiology. The working dilution of the vaccine is prepared in accordance with the attached instructions. From the moment of dilution to the spraying of the vaccine, no more than 30 minutes should elapse. In the first 5 minutes after aerosol spraying, the vaccine is not inactivated or decreases activity slightly if the air humidity in the room is 45-60%. When the air humidity is 80-96%, the inactivation of the vaccine in the aerosol is faster. On the 5-9th day after aerosol vaccination, depression, decreased appetite, shortness of breath and an increase in overall mortality are possible. After 10 days, the listed signs disappear. The total observation period for vaccinated poultry is 14 days. Immunity is formed on the 10-14th day and lasts for 6 months.

Before vaccination with the cloacal method, the bird is not fed for 10-12 hours. For vaccination, use glass, grooved spatulas, sterilized by boiling and preferably separate for each bird. The drug is applied with a spatula to the mucous membrane of the upper fornix of the cloaca, slightly pressing and rubbing in 5-6 times until hyperemia appears. When a bird excretes during the vaccination process, it is repeated. The results are taken into account on the 5-6th day, when a positive reaction to the vaccine should appear, which lasts up to 7-10 days. It manifests itself as inflammation of the mucous membrane of the cloaca, in the form of puffiness, changes in the color of the mucous membrane (from slight redness to dark purple color), the presence of very small hemorrhages in the mucous membrane or, on its surface, serous-mucous exudate. If the post-vaccination reaction is noted in less than 80% of vaccinated birds, the vaccination is repeated.

Combination vaccines are available against ILT and Newcastle disease, as well as against ILT and Marek's disease. The latter is applied individually, by subcutaneous or intramuscular injection. Inactivated vaccines against ILT have been developed, but they are not yet widely used. Genetically engineered vaccines are capable of developing stable immunity, eliminating the possibility of latent infection and reversal of pathogenic properties in vaccine strains of some live virus vaccines against ILT. The use of genetically engineered vaccines is especially valuable in eliminating foci of infection.

Infectious poultry laryngotracheitis affects chickens, turkeys and pheasants. It is characterized by an acute course and hemorrhagic inflammation of the mucous membrane of the trachea, larynx, and sometimes the conjunctiva of the eyes and the death of a bird from suffocation.

Most often, bird laryngotracheitis affects young animals from 1 month of age, but adult birds also suffer greatly from this disease. Therefore, we suggest you talk about the symptoms of laryngotracheitis in chickens and how to treat poultry laryngotracheitis.

Infectious laryngotracheitis of chickens: the causative agent is a virus

The causative agent of this is a virus of the herpes family with a size of 87-110 nanometers. The virus is not resistant to high temperatures: at a temperature of 55 0 C it dies in 10 minutes, at a temperature of 60 0 C in two minutes. At low temperatures it remains virulent for quite a long time: at -20 0 С - up to 105 days, at -8-10 0 С - up to 210 days. At the same time, in frozen carcasses of a sick slaughtered bird, it retains its activity for 1-1.5 years, at room temperature - up to 30 days. In contaminated water chicken infectious laryngotracheitis virus lives no more than 24 hours, in a chicken coop without birds - 6-9 days, in droppings during biothermal treatment it is destroyed after 10-15 days.

The bird laryngotracheitis virus dies in 1-2 minutes under the influence of 1% sodium hydroxide solution, 3% creosote solution, 5% phenol solution. In the presence of a bird, it is recommended to use aerosol preparations based on quaternary ammonium compounds.

Infectious laryngotracheitis of chickens: how they get infected

The source of infection is a sick bird, as well as a sick bird, since it can carry the virus for up to two years. The main mode of transmission of the laryngotracheitis virus in chickens is aerogenic. The pathogen can be spread with infected feed, equipment, water, dust. In addition, beetles - food pests can be carriers of the virus.

Mortality from infectious poultry laryngotracheitis is 2-75%... Since recovered chickens, guinea fowls, pheasants and turkeys carry the virus for quite a long time, it can be very difficult to remove the infection from the farm. In addition, modern vaccines do not guarantee the protection of poultry against the carriage of viruses by vaccine strains and their further reversion to virulent ones.

Chicken infectious laryngotracheitis: symptoms

This virus multiplies in the epithelial cells of the larynx and trachea, causing acute serous-hemorrhagic inflammation with symptoms of "desquamation" of the epithelium and serous edema of the submucosa. In some cases, the disease is complicated by the penetration of a secondary infection, while fibrinous deposits develop on the affected mucous membranes, and degeneration of the epithelium is observed.

The incubation period of infectious poultry laryngotracheitis lasts from 3 to 15 days. There are two main forms:

- Laryngotracheal - classic form. Symptoms of laryngotracheitis in chickens with a classic form: the bird stretches its neck, the neck becomes thicker (swells), breathes with an open mouth, hard, sometimes “croaking” sounds are heard.

- Atypical (atypical) form . Symptoms of laryngotracheitis in chickens with atypical form: the bird has conjunctivitis, panophthalmia (the cornea becomes cloudy, collapses, the eyeball protrudes from the orbit, the bird goes blind), rhinitis.

Infectious poultry laryngotracheitis can occur in three clinical forms:

• Acute form... It is accompanied by a sudden appearance and lightning-fast spread. At the same time, there is a high incidence of poultry, mortality reaches 50%. In some chickens, with an acute form of infectious laryngotracheitis, typical symptoms may not be observed: it does not stretch the neck, and shortness of breath is not heard. At the same time, the chickens cough, wheeze, trying to remove the obstacle from the trachea. On the walls and floor of the hen house, you can see blood clots that the bird coughs up. At autopsy, the main changes are observed in the upper part of the respiratory tract and are characterized by hemorrhagic tracheitis, mucous rhinitis and layering of diphtheria films mixed with blood along the entire length of the trachea.

Typical symptom: hemorrhagic tracheitis (tracheal hemorrhage) that occurs with laryngotracheitis

• Subacute form ... With this form of infectious laryngotracheitis in chickens, the onset of respiratory symptoms is observed after a few days. The incidence is also high, but the mortality rate is slightly lower - 10-30%. When carcasses are opened, pathological changes are less pronounced than in the acute form: in the trachea, in the area of ​​the respiratory fissure, hyperemia, swelling of the mucous membrane, minor hemorrhages, accumulation of foamy, serous-hemorrhagic exudate are noted. Fibrinous-caseous layers in the larynx are easily removed, inflammation of the infraorbital sinuses and conjunctiva is observed.

Caseous plug in the larynx due to laryngotracheitis

• Chronic or moderate form ... This form of infectious chicken laryngotracheitis is most often observed in birds that have had an acute or subacute form. Mortality in one flock does not exceed 1-2% - as a rule, from strangulation. The chronic form of poultry laryngotracheitis is characterized by choking, coughing, nasal and beak discharge. Outbreaks of a moderate form of infection can affect large numbers of birds at the same time. Sometimes lesions develop in the form of sinusitis, conjunctivitis, serous tracheitis. Autopsy reveals diphtheria and necrotic plaques in the trachea, larynx, and oral cavity.

Chicken infectious laryngotracheitis: treatment and prevention

For specific prophylaxis of poultry, the following drugs are used:

Vaccine virus "VNIIBP-U", "Embryo vaccine from strain O" (Ukraine)

Live ILT vaccine (Israel)

- "TAD ILT" virus vaccine (Germany), etc.

Immunity is formed in 4-5 days and lasts about 1 year. Chickens are vaccinated with the threat of infection with laryngotracheitis no earlier than at 17 days of age.

Before, how to treat infectious laryngotracheitis in chickens, a sick bird is placed in a separate room, but both sick and healthy birds are treated.

Treatment of infectious poultry laryngotracheitis it is recommended to carry out with blue iodine with food, as well as inhalation with aluminum iodide or triethylene glycol.

To do this, take a mixture of powdered iodine, ammonium chloride and aluminum powder, place it in metal glasses, which are placed evenly throughout the house, and then add water to each glass (at the rate of 2 ml per 10 grams of powder, 1.2 grams of powder is enough for processing of 1 cubic meter of premises). In this case, the bird is not released from the poultry house while the reaction continues.

Our article provides a simplified, more customized room processing procedure. We quote:

Treatment of cough and wheezing in chickens begins with the fact that the sick bird is urgently isolated, and the healthy one and the room are disinfected. For this, iodine monochloride and aluminum are used. Crystalline iodine can also be found in advice, but pharmacies no longer sell it. Therefore, we take 10 ml of iodine monochloride (a yellow liquid with a pungent odor), and mix in a ceramic container with 1 gram of aluminum (you can take a silver paint or an aluminum dart). As a result of the reaction, yellow smoke is released, we place the dishes in the chicken coop with chickens and close them. The smoke does not last long, about 10 minutes. The dose is indicated for a room of 10 "squares". The procedure should be repeated several times with an interval of 2-3 days and be sure to give the chickens an antibiotic drink, as described in the section on prevention.

In this case, it is best to take antibiotics of the tetracycline series or drugs based on "Tylosin". There are drugs that combine both active ingredients (for example, B-septim). The antibiotic should be given to all birds on the farm where chickens, pheasants, turkeys, guinea fowls are sick with laryngotracheitis, or where there is a suspicion of this infectious disease, in order to protect the bird from possible complications. Antibiotics are drunk or given with food, depending on the manufacturer's recommendations.

However, when treating poultry, you should not take drugs that irritate the mucous membrane of the respiratory tract, such as formalin, chloride turpentine, etc.

A sick bird must be slaughtered and disposed of.

Tatiana Kuzmenko, member of the editorial board

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