ILT of birds is a contagious respiratory disease of chickens of all ages, turkeys, pheasants. The disease was first described in 1925 by Meiel and Titler as infectious bronchitis. For the first time, the virus was isolated in 1930 by Beecham and Bodet from the exudate and epithelial tissues of the upper respiratory tract of a sick bird. A histopathological study conducted by Seyfried in 1931 showed that this disease mainly affects the larynx and trachea, and on this basis it was customary to call the disease infectious laryngotracheitis, this name has survived to the present day. In the former USSR, infectious laryngotracheitis was first described by R. Batakov in 1932, like many foreign authors under the name infectious bronchitis. Later A.P. Kiur-Muratov and K.V. Panchenko (1934), O.A. Bolyakova (1950), S.T. Shchennikov and E.A. Petrovskaya (1954) described it under the name infectious laryngotracheitis.

The disease is registered in all countries with industrial poultry farming. Infectious laryngotracheitis causes a very significant economic damage to the poultry industry: in case of an unfavorable outcome due to the death of poultry, forced slaughter and rejection, it reaches 80%. When infected with infectious laryngotracheitis in chickens, egg production sharply decreases, pullet hens who have had this disease at 4-5 months of age begin to lay eggs with a great delay. In addition, during the illness, weight decreases, which is especially negative when fattening young animals. Due to the long-term carriage of the pathogen by the sick bird, infectious laryngotracheitis among new generations of chickens on the farm becomes stationary if appropriate control measures are not taken.

Causative agent- virus of the herpesvirus family, DNA-containing, enveloped, virion size 40-100nm. The virus is unstable to high temperatures, lipolytic agents, various common disinfectants: 1% NaOH solution, 3% cresol solution (inactivation within 30 seconds). The most effective aerosol application of formaldehyde. In the autumn-winter period, the virus persists indoors for up to 10-20 days, and outdoors for up to 80 days. In the carcasses of dead birds, the virus persists until the onset of decay, and in frozen carcasses at -10-28С up to 19 months. In the tracheal mucus of sick chickens, the virus persists at 37 ° C for 40-45 hours. On the surface of the egg shell in a thermostat, the virus is inactivated within 12 hours. It remains in a lyophilized state for over 9 years.

Epizootology. Under natural conditions, chickens of all ages and breeds, turkey and pheasant are susceptible to ILT. Under experimental conditions, it causes the death of 100% of non-immune chickens.

Z Poultry infection occurs mainly by aerogenic means. In dysfunctional large poultry farms with a continuous system of poultry rearing, the disease can proceed permanently with periodic outbreaks. Most often, the disease occurs in chickens, young chickens after transferring the bird to a cold, damp poultry house, with insufficient ventilation, over-packed planting, inadequate feeding, lack of vitamins and essential amino acids in the diet.

The disease is recorded in all seasons of the year, but its course is exacerbated during periods of sharp climatic fluctuations.

The source of infection is a sick and recovered bird, as well as a vaccinated and latently ill one, which emit the infectious laryngotracheitis virus during the entire economic use, since it remains in the body for up to 2 years. This explains the stationarity of the infection.

The virus from a sick bird is released from the nasal cavity and trachea when coughing and, with small droplets of exudate, an air stream can spread over a distance of up to 10 km. In addition, sick birds shed a virus that can be found on the eggshells.

In vivo, the gates of infection are the nasal and oral cavities, as well as the conjunctiva. Infection occurs when a sick bird comes into contact with a healthy bird through feed and water contaminated with the virus, care items, shoes, clothing of the attendants. Planting poultry in a section of the house where a sick bird has recently been located and not properly sanitized will lead to an outbreak of disease. The sale of virus carriers and poultry with abortive and chronic forms of infection on the market often contributes to the spread of the disease. Rats and wild birds can be mechanical carriers.

Chicks hatched from full-fledged hatching eggs are resistant to infectious laryngotracheitis in the first days of life. The virus is not transmitted transovarially, but it can be found on the surface of the eggshells intended for incubation and, thus, can infect chickens.

In those poultry farms where the disease first appears, it affects birds of all ages. In a stationary dysfunctional farm, it is mainly young animals that are sick, since in dysfunctional farms an adult bird acquires immunity, while in chickens, its presence is noted extremely rarely and it is expressed in a weak form.

Under natural conditions, depending on the virulence of the pathogen, the biological state of the poultry and the veterinary and sanitary state of the farm, young animals become infected starting from 20-30 days of age, but more often outbreaks of the disease are recorded in chickens aged 3 to 9 months.

Pathogenesis. The virus reproduces in the cells of the mucous membrane. In the presence of a highly virulent strain of the virus, hemorrhagic inflammation occurs, accompanied by abundant release of blood into the lumen of the trachea - a hemorrhagic thrombus is formed that completely closes the lumen of the trachea. The bird dies from suffocation. During the period of inflammation, the blood virus spreads throughout the body and can be localized and reproduced in the cells of the conjunctiva and cloaca.

When a less virulent ILT virus enters the body, primary inflammation occurs in the tracheal mucosa, complicated by the activity of the secondary microflora. A dirty gray plug forms in the trachea, closing the lumen. The bird dies from suffocation.

Clinic. The incubation period can last from 2 to 30 days and depends on the virulence and amount of the virus that entered the body, the resistance of the bird. The disease proceeds super-acutely, acutely, subacutely, chronically and abortively. A hyperacute course, as a rule, develops with the initial appearance of the disease in the poultry farm and the penetration of a highly virulent virus strain into the herd. The disease begins suddenly and quickly (within 1-2 days) spreads in the flock, affecting up to 80% of birds. The death of a bird occurs on the second day after the disease.

Respiratory symptoms are pronounced in infectious laryngotracheitis: depression, lack of appetite in birds, coughing and signs of respiratory failure. When inhaling, the bird stretches its neck, a characteristic whistling sound is heard. Through an open beak in the larynx, a hyperemic mucosa and fibrinous overlay on it, plaque in the mucous membrane of the mouth and pharynx are visible. Frequent spasmodic coughs, continuous trembling and head shaking, or continuous attempts to get rid of suffocation are noted. A debilitating cough is accompanied by the release of blood clots and mucous fluid with blood clots. During coughing, mucus and blood clots may be released from the trachea. The bird then appears clinically healthy.

In most cases, conjunctivitis develops - the conjunctival sac is filled with casioid masses. In a sick bird, body weight decreases, egg production drops by 30 - 50%.

The outcome of the disease is favorable and most birds recover when kept in premises with a good microclimate and high-quality balanced feeding.

Pathological changes. In the acute form, conjunctivitis is established, the mucous membrane of the trachea is hemorrhagic inflamed, in the lumen of the trachea - a hemorrhagic thrombus; in the subacute form, hyperemia, swelling of the tracheal mucosa and fibrinous plug. A secondary inflammatory process develops, caused by the microflora of the air in poultry houses. First, curdled diphtheria films are formed, attached to the larynx and the upper part of the tracheal mucosa. Subsequently, mucous exudate accumulates in the trachea and nasal passage, diphtheria films melt somewhat under the influence of microflora. The resulting cork takes on a dirty gray color with brown streaks.

Diagnostics. The emergence of an acute respiratory disease among birds on the farm, accompanied by shortness of breath, wheezing, death of the bird from suffocation and the presence of hemorrhagic or caseous plugs in the lumen of the trachea, makes it possible to make a preliminary diagnosis. But often the disease is atypical or with mild symptoms. The final diagnosis is made on the basis of laboratory studies: the isolation of the virus on CE and its identification by the detection of intranuclear Seyfried inclusion bodies and by serological methods - in the RN, RDP, RIF. The affected larynx, trachea, mucous membranes of the conjunctiva of the eyes from an involuntarily killed bird in the first 7-10 days from the onset of the disease are used as virus-containing material for laboratory studies. During this period of time, the isolation of the virus is most successful, and in the subsequent it is hampered by the layering of conditionally pathogenic microflora.

When making a diagnosis, exclude Newcastle disease, smallpox, infectious bronchitis, contagious rhinitis, pasteurellosis, respiratory mycoplasmosis, vitamin A deficiency.

Newcastle disease affects birds of all ages and is associated with high mortality. At postmortem examination, hemorrhages characteristic of Newcastle disease are found at the border of the glandular and muscular stomachs. Often hemorrhages and necrosis are found on the intestinal mucosa. The causative agent of Newcastle disease belongs to pantropic viruses and is found in all organs and tissues. When 7-9 day old chicken embryos are infected, a hemagglutinating virus is released into the chorioallantoic cavity after 12-48 hours.

Infectious bronchitis spreads in chickens up to 35 days of age. At postmortem examination, lesions of the bronchi and lungs are found. Infection of 9-day-old chicken embryos into the allantoic cavity causes dwarfism or curling.

A contagious rhinitis is chronic. There is no hemorrhagic and fibrinous inflammation, blood clots and caseous plugs in the trachea and larynx. In a bacteriological study, the causative agent of an infectious rhinitis is isolated - B. hemophilus gallinarum.

Smallpox is characterized by skin lesions and difficult-to-remove films on the oral mucosa. When 7-9 day old chicken embryos are infected on the chorioallantoic membrane, foci of necrosis are formed, similar to foci of necrosis caused by the infectious laryngotracheitis virus, therefore, serological identification is necessary.

Pasteurellosis of the chronic form is differentiated by the detection of microbes bipolarly perceiving color in blood smears of a sick bird. When sown on simple nutrient media, they release Past. multocida, pathogenic for pigeons and white mice.

Respiratory mycoplasmosis is a slow-onset disease, accompanied by an insignificant mortality of poultry. The carcasses of dead birds are often severely emaciated. At postmortem examination, a lesion of the air sacs is found. When sowing on special nutrient media from the air sacs and lungs, M. gallisepticum.

With vitamin deficiency - and the main changes are localized in the mucous membrane of the esophagus. They find millet formations there. When chickens are infected with a suspension of tracheal exudate, the disease cannot be reproduced.

Elimination and prevention of disease... The prevention of ILT consists of measures that provide for the protection of farms from the introduction of the pathogen. Flocks of birds are completed from farms free of ILT, birds of different ages are placed in territorially isolated zones: poultry houses are filled with birds of the same age. Strictly observe inter-cycle preventive breaks with sanitation of premises, disinfect imported hatching eggs, containers and transport, ensure separate incubation of eggs imported and obtained from their own parent flocks; chickens obtained from imported eggs are raised separately from the rest of the poultry on the farm; create optimal zoohygienic, especially in relation to the microclimate, conditions of detention.

At poultry farms, for the prevention of respiratory diseases, the treatment of poultry with vapors of chlorine and turpentine, iodine triethylene glycol and antibiotics is widely used. The antiviral chemotherapeutic drug izatizone and lozeval has been successfully tested.

In the Russian Federation, two vaccines have been created from the VNIIBP live virus and a vaccine from the NT clone obtained from the TsNIIP strain. Vaccines are used in accordance with the current guidelines and methods of rubbing into the mucous membrane of the cloaca and aerosol. Ocular and oral methods of immunization have been developed at VNIVIP and VNIVViM.

Smallpox, NB, IB, colibacillosis and respiratory mycoplasmosis negatively affect the formation of post-vaccination immunity in ILT. To increase the effectiveness of specific prophylaxis of ILT, it is necessary to carry out preliminary measures against these diseases. Immunization of poultry against ILT 2-8 days after immunization against NB and smallpox causes a statistically significant decrease in the intensity of post-vaccination immunity against this disease. In this regard, in order to increase the effectiveness of immunization against ILT, it is advisable to carry out it with an interval of 10-15 days before or after vaccination against NB and smallpox.

In a dysfunctional economy, farm, zone, restrictions are imposed and they act in accordance with the instructions for combating ILT. All healthy birds are immunized. A negative factor when using a live virus vaccine is the potential for the spread of the virus and the appearance of a virus-carrying bird, which leads to a wide spread of infection in the area. Therefore, in areas where the disease is not endemic, but an outbreak has occurred, it is worth resorting to replacing (slaughtering) the entire livestock and conducting thorough cleaning and disinfection before purchasing a new batch of poultry.

Restrictions are lifted 2 months after the last case of slaughter of sick and recovered birds, and the completion of the final measures.

Laryngotracheitis is becoming an increasingly common infectious disease in chickens every year. Today the problem is relevant for England, Sweden, France, Yugoslavia, Holland, Italy, Canada, Indonesia, Hungary, Australia, Romania, USA, Poland, Spain, Germany, New Zealand, Russia.

Outbreaks are recorded in almost every region of the indicated countries. Especially large poultry farms suffer from infection, but small farms cannot avoid cases of laryngotracheitis. A breeder of any size must have an understanding of the pathology and how to cure it.

Infectious laryngotracheitis is a respiratory disease. The causative agent is the Herpesviridae virus. Most often, hens are infected, but other poultry (pheasants, peacocks, ornamental quails) are also susceptible to infection. Laryngotracheitis is also common among pigeons.

Infectious laryngotracheitis is a respiratory disease.

The first name of the disease is tracheolaryngitis. It was opened in 1925 by Titzler and May in the USA. In 1931, parts of the name changed places, as they have remained until now. For a long time, the infection was associated with bronchitis, but it was transferred to the status of an independent problem.

The pathogen virus is distinguished by its vitality in any climate, resistance to many drugs. It can be quite difficult to defeat him, especially when it comes to complex forms of manifestation. Laryngotracheitis is expressed in impaired respiratory function. Infection is localized in the trachea and larynx, spreading to the conjunctiva, which causes lacrimation.

Outbreaks of mass infections are seasonal. Most often they occur in spring and autumn with high humidity and low air temperatures. In winter, the virus actively settles in birds with low immunity.

The metabolism of harmful cells occurs slowly, so the symptoms may not appear immediately, but within 2 years from the moment of infection. As poultry live in a community environment, the spread of the disease is rapid. Up to 80% of the flock can be affected per day.

Recovered individuals acquire their own immunity, but for a long time they spread the accumulated virus.

As a rule, the transfer is carried out by airborne droplets with particles of cough sputum. Even a person can become a carrier if the exudate of chickens gets on clothes or equipment. The disease is transmitted to humans through prolonged contact with an infected livestock, but infection through meat, feathers and eggs is excluded.

Laryngotracheitis does not have an age binding, however, young animals up to 100 days of life are more difficult to tolerate. In the northern regions, chicks often fall ill up to 20 days of age. Recovered individuals acquire their own immunity, but they spread the accumulated virus for a long time, so they cannot be introduced into an unvaccinated herd. Eggs from hens with laryngotracheitis are not incubated.

Diseases are indirectly promoted by poor ventilation, too high humidity, drafts of unsanitary conditions in the chicken coop, unbalanced nutrition and vitamin deficiencies. Mortality from infection reaches 15%.

The appearance of laryngotracheitis on a farm is always associated with impressive economic damage. The livestock often falls ill completely or in a greater percentage. Many individuals die (especially young animals), which immediately deprives the breeder of a significant part of future meat products.

Because of outbreaks of laryngotracheitis, most of the livestock perishes, which bears great losses.

In addition, the owner of the flock is forced to spend money on medicines, veterinarians, transportation of a specialist or birds to an appointment. Sometimes inventory replacement is required. Not a small amount is spent on prevention - disinfectants, vaccines.

The laryngotracheitis virus spreads primarily along the mucous membranes of the nasopharynx, mouth and conjunctiva. The incubation period is from 1 to 3 days, but it happens that the symptoms of infection appear by the end of the first day.

It happens that the disease, colibacillosis, hemophilia, bronchitis or other bacteriological infections. To confirm the diagnosis, an analysis is required for the isolation of viruses from the pathological material.

Important. Experts say that with a careful approach, laryngotracheitis can be suspected in 10-15 minutes, and cured in no more than a week.

Profuse lacrimation from the eyes, a runny nose, an open beak should instantly arouse suspicion in the owner... Often, due to the swollen larynx, the bird experiences pain and refuses to eat. Of the general symptoms, there is also a blue discoloration of the scallop and earrings, a noticeable weakness of the bird. The rest of the signs depend on the form of the course.

With laryngotracheitis, chickens have watery eyes, they breathe heavily, refuse to eat.

Symptoms of the hyperacute form

With this form, the symptoms appear massively and suddenly.

The signs are distinguished by their bright severity, a rapid increase in intensity:

• Heavy breathing with whistling and wheezing, reaching the point of suffocation (worse at night).
• The bird pulls its neck and shakes its head in the hope of breathing more freely.
• Paroxysmal, violent cough, often with bloody sputum.
• The chicken lies a lot with closed eyes.
• Slime is observed on the floor and walls in the house.

The hyperacute form is considered the most deadly. It can kill up to 50% of the livestock. It is the most difficult to treat as it requires very quick action.

The acute form of laryngotracheitis does not manifest itself as sharply as hyperacute. Chickens show symptoms on several heads at intervals.

• Passive attitude towards feedings and general activity.
• On examination, white cheesy or slimy masses in the beak, redness, swelling of the mouth and larynx.
• Audible whistles during inhalation and exhalation.

In the acute form, chickens do not eat well, become apathetic.

An acute course is dangerous with death due to blockage of the lumen of the larynx with accumulations of secretions. If an individual suffers from an attack of suffocation, she needs urgent help in coughing up and removing the edema. This form, without therapy or with its insufficiency, often develops into a chronic one. The mortality rate when receiving the correct treatment does not exceed 10%.

Most of the time, symptoms are not pronounced.

They appear at regular intervals and increase before the death of the chicken:

• Falling indicators of weight gain and egg production.
• Repeated attacks of spasmodic coughing to suffocation (even at long intervals).
• Conjunctivitis, sometimes photophobia.
• Frequent discharge of mucus from the nostrils.

With a drop in egg production, the preservation of the quality of the egg is characteristic. Chronic morbidity and mortality are in the region of 1-2%.

In chronic laryngotracheitis, symptoms only occur from time to time.

Conjunctival symptoms

Usually occurs in chicks 10-40 days old, but it can also affect adult chickens:

• Inflamed, reddened white of the eyes, photophobia.
• Finding the third eyelid on the eyeball, lids sticking together.
• Mucous and frothy discharge from the eyes.
• Loss of orientation due to vision problems.
• Fading of the cornea.
• The trachea may be clogged with blood clots, the throat is cherry-colored.

The conjunctival form is often curable in 1-3 months. The main danger is the complete loss of vision due to atrophy of the eye tissues.

The atypical form of laryngotracheitis is imperceptible. As a rule, the individual carries and spreads the virus, but itself has no obvious symptoms and danger of death. This happens with strong immunity or when the bird has already been cured.

The main symptoms can be seen only when examining the larynx - swelling, redness, small ulcers are possible due to the destroyed epithelium.

The atypical form of laryngotracheitis is imperceptible.

Laryngotracheitis therapy is considered by many to be unjustified. From an economic point of view, it is considered more profitable to purchase a new herd than to treat a sick flock of chickens. If the old individuals are preserved, the virus will still remain on the farm, will spread to young animals, which will need to be regularly vaccinated.

Treatment of the disease is offered according to a nonspecific scheme:

1. Providing high-quality heating, ventilation in the poultry house, increasing the content of vitamins in the feed.
2. Drinking antibiotics of a wide range (tetracycline, norfloxacin, ciprofloxacin). Powdered furazolidone is mixed into food (8 g of medicine per 10 kg of feed).
3. Iodotriethylenegylcol, gentamicin, lactic acid are sprayed in an aerosol in the poultry house in the presence of livestock.
4. If it is possible to isolate the chickens, they are disinfected with a 15-minute rush of a mixture of turpentine (2 mg) and bleach (20 mg) per 1 cubic meter of space.
5. Individuals are given vitamin mixtures such as RexVital, Aminivital, Chiktonik, ASD-2 up to 1 ml per 100 chickens.

With laryngotracheitis, chickens are drunk with antibiotics, for example, tetracycline.

Important. When the old livestock is slaughtered, the premises must be disinfected along with the equipment before settling in a new one.

Disease prevention

Prevention is carried out in three areas:

1. Compliance with sanitation in the poultry house, housing density, regular inspections, adequate feeding. Separation of livestock by age, quarantine of individuals before moving in. Periodic disinfection of the chicken coop with Virokone or Glutex with a flock.
2. The use of vaccines for the formation of immunity against the causative agent of laryngotracheitis. Cloacal, intraocular, oral, aerosol administration. In affluent areas, vaccination is not recommended, so as not to artificially cause outbreaks.
3. If an infection is detected more than 2 times, the export of chickens from the farm is prohibited by law.

There are two types of vaccines for the prevention of laryngotracheitis. The first ones are made on the basis of chicken embryos. They give strong protection to the immune system against a particular virus, but can cause serious complications in the body as a whole. For the second, cell culture acts as a raw material. Such varieties do not cause adverse reactions, but protection from them cannot be called serious.

Some farmers vaccinate poultry with drugs for laryngotracheitis.

The most popular vaccines against infectious laryngotracheitis in the veterinary environment are those that are sold in packs of more than 1000 doses.

These include:

• Avivak, Russia;
• Intervet, Netherlands;
• AviPro, Germany;
• Vaccine from the VNIIBP strain, Russia;
• Nobilis ILT.

Infectious laryngotracheitis of birds - Larin - gotracheitis infectiosa avium. Synonym - tracheolaryngitis.

Infectious laryngotracheitis (ILT) is a contagious viral disease of birds, characterized by damage to the mucous membrane of the upper respiratory tract and eyes in chickens, turkeys and pheasants.

Historical background, distribution and economic damage. Infectious avian laryngotracheitis was first reported in the United States in 1924.

In 1925 this disease was described by May and Titler under the name tracheolaryngitis. Other American researchers (1925-1930) described it as infectious bronchitis. Later, the independence of these two diseases was proved, and histological examination showed that with this disease, the larynx and trachea are mainly affected. The Special Committee on Avian Diseases in the USA (1931) proposed to call this disease infectious laryngotracheitis, which persists to the present day. The disease spread to almost all states in the United States and then spread to »Europe, Australia, New Zealand and Asia.

In the USSR, infectious laryngotracheitis of birds was first described by RT Botakov in 1932 under the name infectious bronchitis.

Later, A.P. Kiur-Muratov and K.V. Pachenko (1934), S. A. Polyakova (1950), T. S. Shchennikov and V. A. Petrovskaya (1954) described it under the name infectious laryngotracheitis. Currently, infectious laryngotracheitis tends to spread and is registered in many farms of the Russian Federation.

The economic damage in this disease consists of losses as a result of the death of sick birds, forced slaughter, a decrease in egg production, weight gain of birds, and huge costs for measures to stop the infection.

The causative agent is a DNA-containing virus of the herpes virus family (Herpesviridae), subfamily Alphaherpesviridae. Virions are spherical in shape, their diameter is 87-97 nm. The virus in the trachea and tracheal exudate lasts up to 86 days at a temperature of 2-4 ° C, indoors - up to 30 days, on the eggshell - up to 24-96 hours. In the absence of sanitation, the virus penetrates the egg white and yolk through the shell and can remain virulent up to 15 days. In frozen carcasses, the herpes virus remains virulent for up to 19 months. In artificially infected fluff and grain feed, the virus survives up to 154 days. 1% alkali solution, 3% cresol solution inactivate the virus in 30 s.

Virus strains circulating in the country are related in antigenic respect, but differ from each other in virulence and ability to be cultivated in chicken fibroblast cultures. Some strains have hemagglutinating properties.

Epizootological data. In natural conditions, only poultry, in particular chickens of all ages and sometimes pheasants, are susceptible to infectious laryngotracheitis, but in laboratory conditions it is possible to infect turkeys and ducks, but without showing symptoms of the disease.

Chickens aged 3 to 9 months are susceptible to infection. Monthly ILT chicks do not get sick, despite the fact that the virus grows in chicken embryos, day-old chicks are free from the disease.

The main source of infection is a sick and recovered bird.

Recovered birds are not susceptible to infection, but for a long time (up to 2 years) they are virus carriers and continue to excrete the virus into the external environment. Infected birds constitute the main and long-term source of the virus, because, like all herpes viruses, the infected animal continues to carry and shed the virus throughout its life.

The main routes of transmission of the virus are aerogenic (airborne) and contact. The respiratory system is the gateway to infection. The virus is transmitted from sick birds to healthy ones mainly through infected air. From a dysfunctional poultry house, the virus spreads with air masses over a long distance - up to 10 km. Transmission of the virus is possible with slaughter products, down and feathers, incubation waste, containers, bedding, feed.

With the contact route, all livestock are re-infected in a short period, especially in broiler poultry farming.

The infectious laryngotracheitis virus is not transmitted transovarially.

The disease spreads in all seasons of the year, but more often in summer and autumn. The disease often occurs when poultry are kept in damp, dusty, gas-polluted, cold and draughty rooms, with insufficient air exchange, overestimated planting of birds in poultry houses and the presence of diseases.

The mortality rate of birds with ILT is on average 15%, sometimes it rises to 30-80% in acute course, higher than in Newcastle disease. The incidence in chickens up to 3 months of age can reach 90.5-100%, in chickens - up to 96.2%. In conjunctival ILT, the incidence is 5-87%.

A person can also be sick with infectious laryngotracheitis, but the disease is mild with a successful outcome.

Pathogenesis. The ILT virus, having penetrated the upper respiratory tract, enters the epithelial cells of the mucous membranes of the larynx and trachea, and in some cases also other parts of the respiratory system. In the affected cells of the epithelium, nuclei multiply rapidly without dividing the cytoplasm. Soon, cell degeneration occurs and their rejection into the lumen of the affected parts of the respiratory system.

The body's response to the penetration of the virus is expressed by a sharp blood filling of the vessels of the mucous membrane of the larynx, trachea, bronchi, pulmonary parenchyma and the wall of the air sacs, edema of the own layer of the mucous membrane of the upper respiratory tract, interstitial tissue of the base of the wall of the air sacs, cellular infiltrative and proliferative reactions, desquamation of the respiratory epithelium and effusion of exudate into various parts of the respiratory system.

Subsequently, the ILT virus enters the bloodstream through the damaged vascular walls, where it is detected within 24 hours after infection.

Sharp desquamative processes of the respiratory epithelium (especially in the larynx and trachea) are the result of not only the direct action of the virus, but also the result of a violation of anatomical connections due to severe edema of the own layer of the mucous membrane.

Increased vascular permeability, as well as their rupture due to mechanical reasons (cough), lead to hemorrhages in the tissues and lumen of the larynx and trachea, which, in turn, greatly complicates the act of breathing, and blockage of these organs (their lumen) with caseous plugs leads to death birds as a result of asphyxiation. The secondary microflora also has a certain influence on the severity of changes.

In the conjunctival corner of the eye, in addition to serous exudate, fibrinous-caseous masses accumulate, and sometimes turbidity develops.

Clinical signs. The incubation period for infectious laryngotracheitis is on average 4-10 days (with fluctuations from 2 to 30 days).

The course of infectious laryngotracheitis can be fulminant, acute, subacute

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With a fulminant course, the disease begins suddenly and spreads rapidly throughout the herd within a few days.

The morbidity rate is extremely high and the mortality rate is also extremely high - it can be 50-70% of the total number of sick poultry. In some individuals, clinical signs of the disease rarely appear for a period of more than 2-3 days before death, some of them die without previously showing symptoms. It is rare to see a clear loss of body weight and often the bird with the highest body weight is sick. Respiratory symptoms appear immediately with no visible signs. There are obvious breathing difficulties, the bird stretches its head and neck, closes or closes its eyes and gasps for air for a long time. This is accompanied by gurgling and wheezing. There is a spasmodic cough, and the head shakes violently in an attempt to clear obstructions in the trachea. When coughing, clots of blood and mucus with blood inclusions are released, which can be seen on the walls and on the floor of the house. The head is usually cyanotic. Foamy discharge from the eyes and nostrils is sometimes observed.

With a subacute course in most birds, the disease progresses more slowly. Difficulty breathing, coughing, and other respiratory symptoms can last for several days before death. The morbidity rate is still high, but the mortality rate is lower, it can affect from 10% to 30% of diseased birds. This form of the disease can predominate throughout the period or occur at the end of an extremely acute outbreak.

The laryngotracheal form of the disease can be observed with a fulminant and acute course in the first 5-7 days. The bird can hear whistling, wheezing and croaking sounds, coughing. With this form, there is a partial or complete blockage of the larynx and trachea with fibrinous films, plugs and exudate. At the same time, the bird breathes with an open beak, which leads to a violation of the breathing rhythm and asphyxia.

In a chronic course, the level of disease in a herd can be 1-2%, but most of the sick bird invariably dies from suffocation, sometimes after different periods of time, often after long periods. The main symptoms: poor growth, coughing spasms and choking, if the bird is handled and in a state of excitement - discharge from the nostrils and eyes and a decrease in egg production.

Egg production decreases on the 9-10th day from the onset of the disease by 37.4-40% (Fig. 2). However, the quality of the eggs does not change.

In a chronic course, the disease manifests itself in a conjunctival form more often in chickens aged 10-15 days, but it can also be in older ones. With the conjunctival form of the disease, photophobia, lacrimation, sticking of the eyelids and deformation of the palpebral fissure are observed in chickens. Hemorrhages are visible on the mucous membrane of the eyes, accumulations of fibrinous mass are noticeable under the third eyelid, and atrophy of the eyeball occurs.

In some birds, corneal opacity and ulceration are noted, accompanied by partial or complete loss of vision.

The conjunctival form lasts from 20 days to 2-3 months and leads to depletion and increased culling of birds.

With a mixed form of the disease, signs of all forms appear, but it progresses more severely, and, as a rule, ends in an unfavorable outcome.

The atypical form of the disease proceeds with erased clinical signs.

Pathological changes. In the laryngotracheal form, the main changes are found in the larynx and trachea. The lumen of these organs in some birds is filled with different amounts of catarrhal or catarrhal-hemorrhagic exudate, some with blood clots; in other birds, it contains fibrinous-caseous masses, often in the form of gray-yellow plugs, partially or completely blocking the lumen of the larynx, especially its slit. Caseous plugs are usually easily detached from the mucous membrane. The mucous membrane itself is sharply hyperemic, unevenly thickened and permeated with numerous punctate and banded hemorrhages, especially in the larynx and upper trachea.

With some enzootypes of infectious laryngotracheitis, the hemorrhagic accent of inflammation is mild or completely absent. In these cases, catarrhal or fibrinous exudate is found in the lumen of the larynx and trachea, and in some birds, fibrinous-caseous plugs of gray-yellow color.

Similar changes in the lungs often develop in a large percentage of cases in chicks infected in the trachea; in case of contact infection, catarrhal pneumonia is rarely observed.

The defeat of the air sacs in infectious laryngotracheitis is also relatively rare. However, with the experimental method of infection, especially with the intratracheal method, aerosacculitis occurs in a significant number of birds.

The wall of the air sacs in the event of a lesion is diffusely or focal thickened, the vessels are overflowing with blood. In the cavity of the air sacs, a serous foamy exudate with fibrin clots or grains of fibrinous-caseous masses is found. It should be borne in mind that a large percentage of damage to the lungs and air sacs is often the result of an associated infection of respiratory mycoplasmosis and infectious laryngotracheitis.

Of the other changes found on autopsy, some researchers note catarrhal enteritis, cloacitis, lesions of the bursa and hyperplasia of the spleen.

The conjunctival form (atypical) of infectious laryngotracheitis can occur only with damage to the conjunctiva or in combination with the laryngotracheal form of the disease.

With some enzootics, serous conjunctivitis is found in the vast majority of birds. In this case, the conjunctiva is hyperemic, edematous, sometimes with punctate hemorrhages. In some birds, swelling of the eyelids is noted, especially the lower. In some hens and chickens, there is an accumulation of fibrinous-caseous masses, sticking of the eyelids, opacity of the cornea, sometimes with the development of panophthalmitis.

Histological changes. Histological examination of the larynx and trachea reveals pronounced edema and cellular infiltration of the mucous and submucous membranes. Sometimes swelling of the mucous membrane destroys its normal structure, which leads to the presence of perivascular hemorrhage. 3-5 days after infection, continuous cellular infiltration with small lymphocytes, histiocytes, plasma cells and eosinophilic leukocytes is noted in the larynx. However, characteristic is the detection in the nuclei of epithelial cells of the affected mucous membrane of the larynx, trachea and bronchi of intranuclear inclusions (acidophilic bodies) - virus-specific nuclear inclusions. They are found in cells with an enlarged nucleus. They can be round, sausage or diplococcus-shaped and occupy half of the cell nucleus. An unpainted area is visible around the nuclear inclusion.

Immunity. The serum of birds and hyperimmune birds that have recovered from infectious laryngotracheitis contains specific neutralizing antibodies. Recovered birds acquire strong immunity, which is passed on to offspring through eggs.

Diagnosis. Epizootological data and symptoms of the disease in acute course are characteristic of infectious laryngotracheitis (ILT). However, the chronic course of ILT cannot be distinguished from other respiratory diseases.

The virus must be isolated to confirm the diagnosis. The material for the study is fresh corpses, a clinically sick bird (4-5 heads), exudate from the trachea, as well as scrapings of the affected mucous membrane of the larynx and trachea.

This is done as follows:

Sowing of tracheal exudate on chorion-allantoic membranes;

Sowing on cell cultures;

RDP with tracheal exudate or infected chorion-allantoic membrane (CAO) using hyperimmune sera;

Detection of herpes viruses by electron microscopy: in the tracheal exudate; growth in KhAO; immunofluorescence; Elisa using monoclocal antibodies to ILT virus or ELISA;

Histological examination - detection of virus-specific intranuclear inclusions in the epithelium of the mucous membrane, Safe-Reed corpuscles.

The identification of the virus is carried out by the neutralization reaction (RN) on 10-11-day-old chicken embryos with specific antisera of hens or rabbits.

Differential diagnosis. Clinical signs of infectious laryngotracheitis are similar in some cases to other avian diseases, therefore, when diagnosing them, it is necessary to exclude Newcastle disease, respiratory mycoplasmosis, infectious bronchitis, smallpox, infectious rhinitis, chronic pasteurellosis, hypovitaminosis A, ammonia blindness. Respiratory mycoplasmosis spreads slowly. Among the diseased, a large number of emaciated birds - "crackers", fall ill mainly young animals 5-7 months of age. Autopsy reveals lesions of the air sacs characteristic of respiratory mycoplasmosis - aerosacculitis - their walls are thickened, opaque, covered with fibrinous films. Poultry mortality is insignificant. When sowing on special nutrient media, the pathogen Mycoplasma gallicepticum is isolated from the air sacs and lungs; with retrospective diagnosis by enzyme-linked immunosorbent assay (ELISA), specific antibodies are isolated.

Infectious bronchitis of chickens is observed in them up to 30 days of age; proceeds mainly with damage to the bronchi, lungs and the lower part of the trachea. Infection of 9-day-old chicken embryos causes the death of embryos at the end of incubation with characteristic signs of dwarfism, mummification without bacterial decomposition. The final diagnosis is established by the isolation of the virus in chicken embryos.

Smallpox is diagnosed by the presence of smallpox lesions on the crest, barbs or diphtheria intractable overlays on the oral mucosa, as well as typical folliculitis that occurs 4-8 days later at the site of application of vaccinated material. In the atypical form - by the isolation of the virus in chicken embryos.

The infectious rhinitis is chronic; at the same time, a watery-mucous exudate is released from the nasal openings. There is no hemorrhagic and fibrinous inflammation, blood clots and caseous plugs in the trachea and larynx. In a bacteriological study, the pathogen Bact is isolated. hemophillus gallinarum.

Chronic pasteurellosis. When sowing on conventional nutrient media, the causative agent of this infection, Pasteurella multocida, is isolated, which is pathogenic for laboratory animals (white mice, pigeons, rabbits).

Hypovitaminosis A. To exclude it in conjunctival form, it is necessary to examine liver samples for the content of vitamin A. Investigate both sick chickens and those who do not have clinical signs of the disease, but are in contact with patients. With hypovitaminosis A, hemorrhagic inflammation is not observed and there are no caseous-fibrinous plugs in the larynx and trachea. At the same time, changes are found mainly on the esophageal mucosa in the form of millet dense nodules, but histological studies and bioassay do not confirm infectious laryngotracheitis.

Ammonia blindness occurs when the amount of ammonia in poultry houses is too high. With good ventilation, the disease quickly stops.

Treatment. Due to the fact that ILT causes significant economic damage to poultry farms, an intensive search for drugs against this disease is underway.

The most promising use of such drugs, which can be used in any epizootic situation, complicated by a second infection.

Satisfactory results are obtained by using a 0.2% sulfamethasan solution, 0.125% sulfazole with water for 2-6 days in a row, a furacillin solution at a concentration of 1: 5000 instead of drinking water and furazolidone 0.04-0.06% daily diet for 2-6 days.

Iodinol has therapeutic and prophylactic properties against ILT. It is recommended to add the drug to water and feed at the rate of 0.25-0.5 ml per head per day. Particularly good results were observed when iodinol was given at a dose of 0.5 ml per head together with 5 mg of nystatin. For the treatment of the upper respiratory tract in birds, it is recommended to irrigate the mouth, nose and eyes with 0.02% gramicidin solution.

Positive results were obtained from the use of a mixture of penicillin (at a dose of 5-10 thousand units) in a 0.5% solution of novocaine given daily for 2-3 days.

A. A. Zakomyrdin, V. E. Zuev (1978) proposed triethylene glycol iodine, which is an oily liquid, to combat infectious laryngotracheitis. Iodine-triethylene glycol aerosol disinfects the surrounding air in the poultry house, has a virucidal and bactericidal effect.

A 30% aqueous solution of glycosan is used aerosolically.

At the Department of Poultry and Poultry Diseases MBA (BF Bessarabov, 1992), a method has been developed for the use of isatizone against viral laryngotracheitis. It is an oily liquid of dark yellow color, bitter taste, with a specific odor, contains methisazone mixed with dimethyl sulfoxide and polyethylene glycol-400. Izatizon is recommended for the prevention and treatment of infectious chicken laryngotracheitis.

For aerosol disinfection of the air in the presence of a bird, glutex is used, Virkon S.

Specific prophylaxis. For prophylaxis, live embryonic vaccines are used, that is, the virus grown on chicken embryos, and cultural ones - on cell culture. In poultry farms, the following are used:

Dry virus vaccine from the VNIIBP strain against ILT; w embryo-virus vaccine against ILT;

Dry liposomal virus vaccine from the VNIVIP strain against infectious laryngotracheitis of birds;

Combined dry vaccine against Newcastle disease (NB) and avian infectious laryngotracheitis (ILT);

Virus vaccine from clone "NT" strain TsNIIPP.

Virus vaccines are used aerosol, cloaca, ocular, enteral.

Immunity begins on the 7-10th day and remains during the entire economic use of the bird. Vaccination is carried out only in dysfunctional farms, since in some cases up to 2% of chickens become ill with ILT on the 8-15th day. Therefore, vaccinated chickens are raised in isolation.

Prevention and control measures. In a prosperous household. In order to prevent the occurrence of infectious laryngotracheitis in poultry farms, a set of measures should be carried out in accordance with the instructions.

In a dysfunctional economy. When a diagnosis is made for ILT, the farm is considered unsuccessful and the following restrictions are introduced in it: it is not allowed to take out poultry, feed, equipment and implements from the farm, and during an acute outbreak - to move the poultry inside the farm.

When ILT occurs in a separate poultry house, all birds from it are sent to the slaughterhouse. Thorough mechanical cleaning and disinfection of the dysfunctional poultry house is carried out. Litter after processing the premises with disinfectant solutions is subjected to biothermal disinfection.

In unfavorable for ILT farms, the conditions of keeping and feeding are improved for poultry. Poultry of different age groups are placed in geographically separate zones, with the necessary veterinary breaks.

The import of breeding eggs and day-old chicks is allowed; export of eggs to the distribution network after disinfection, export of conventionally healthy poultry to meat processing plants, export to catering establishments of carcasses obtained from the slaughter of conventionally healthy poultry, export after disinfection of down and feather to processing plants.

The acquisition of poultry houses and zones with healthy young of the same age is carried out at least 30 days after the acute course of the disease in other poultry houses of the farm.

Inter-cycle preventive breaks with cleaning and disinfection of premises are carefully observed.

Restrictions from a dysfunctional economy are removed 2 months after the last case of death or slaughter of sick poultry, the final veterinary and sanitary measures and the absence of the release of the infectious laryngotracheitis virus.

The export of birds to other farms for completing the parent flock is allowed no earlier than 6 months after the restrictions are lifted.

Disease prevention and control measures include a set of organizational measures, the use of chemicals that promote disinfection of indoor air in the presence of birds and partial inactivation of the virus in the upper respiratory tract, and immunization of birds with vaccines.

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 ° C up to 3 minutes, at 75 ° C - 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 stability, 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. 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 farms that are dysfunctional in terms of infectious laryngotracheitis, with seasonal rearing of young animals (in spring and summer), chickens get sick in summer and early autumn, pullets in late autumn, after being transferred to a 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 the ILT virus infects guinea fowl embryos of 9-, 11-, 15-, or 18-day incubation, CAO lesions appear in 3-5 days. A feature 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 poultry, 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 able to develop stable immunity, excluding 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.

As the name suggests, this is viral chicken disease affects the mucous membrane of the larynx and trachea. Sometimes conjunctivitis and nasal involvement are associated symptoms. If the disease is not cured in time, you can lose many of your domestic hens. Consider laryngotracheitis in chickens, the treatment of which is so important to start on time and correctly.

Description

Laryngotracheitis is a dangerous infectious disease that causes the activity of viruses from the herpes family. As practice shows, it is quite stable, therefore, after the incubation period, it can remain active for up to two years. In addition to chickens, all poultry, as well as pigeons, are ill with this disease.

Laryngotracheitis in chickens occurs in two main forms: acute and hyperacute. At the same time, the acute course of the disease causes mortality in 15% of cases, while the hyperacute form - in 50-60% of cases. In some animals, the disease occurs in a chronic form of manifestation.

Chickens of all poultry, and especially chicks aged 30 days - 8 months, are the most susceptible to the disease. It is important to note that the virus is also transmitted to humans if they often come into contact with infected birds. A person can be affected by the larynx and trachea, the skin of the hands, as well as bronchitis due to the disease.

As for chickens, laryngotracheitis most often manifests itself during periods of unstable temperatures, off-season, with non-compliance with sanitary standards, as well as with low immunity of birds. Old and adult birds that have had an illness at an early age acquire immunity, so they do not get sick later. But they are carriers of the virus. The main route of infection is airborne.

Symptoms of manifestation

As we have already said, laryngotracheitis occurs in chickens in two phases - acute and hyperacute. The latter form often occurs suddenly in dysfunctional farms, where the disease has not previously been recorded. In this case, almost all chickens (up to 80%) can become infected in the first day. The main indicator of this ailment is the heavy, almost impossible breathing of the bird. Then there is a cough, attacks of suffocation, coughing up. Recovered birds can keep wheezing for a long time, suffer from conjunctivitis, although outwardly they will look healthy.

Symptoms of the hyperacute form

• asthma attacks;
• chickens shake their heads;
• coughing up blood or other secretions;
• low mobility of birds;
• swelling of the larynx and the presence of curd discharge on the mucous membrane;
• lack of appetite and egg-laying;
• wheezing.

Symptoms of the acute form of the disease

Acute laryngotracheitis also affects the respiratory system and spreads in the herd in about 10 days. Mortality in these cases with proper treatment is low, not exceeding 20%. Typical signs:

• poor appetite;
• lethargy and inactivity;
• wheezing and whistling when breathing;
• cough;
• laryngeal edema;
• the presence of cheesy discharge.

In chickens, laryngotracheitis is also accompanied by severe conjunctivitis. Many even lose their sight.

Treatment methods

If laryngotracheitis is found in chickens, treatment should be carried out immediately. However, we note that a drug to combat the disease of birds has not yet been created. Various antibiotics are used in practice, which can only reduce the activity of the virus. For example, the use of biomycin reduces overall mortality. When taking medications, laying hens must necessarily receive additional vitamins in the diet, in particular A and E.

The basic rule for laryngotracheitis is good prevention, which consists in proper feeding of birds, as well as in strict observance of sanitary and hygienic standards. To disinfect the chicken coop, a mixture of chlorine-turpentine is used. Also, as a prophylaxis of the disease on large farms, special vaccines are used.

Video "Some rules for vaccination of broilers"

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