Avian infectious laryngotracheitis (ILT) is an acute infectious viral disease. In sick birds, hemorrhagic inflammation of the larynx and trachea develops, sometimes the lesion spreads to the conjunctiva. Lethality - 2-75% of the flock. Birds from the order Galliformes are susceptible to the disease: chickens of all areas of productivity, guinea fowls, pheasants, less often turkeys. Occasionally, cases of infection of ducks and pigeons are recorded. Human infections have been reported. The risk group includes employees of laboratories and biofactories - those who, by the nature of their activities, often come into contact with vaccines and highly virulent strains. Poultry products do not pose a danger to humans.
The causative agent of the disease is a DNA genomic virus from the herpesvirus family. Known weakly virulent and virulent strains of the virus that do not have antigenic differences. Under direct sunlight, the virus is inactivated within 7 hours. When heated to 55 degrees, the infectious agent dies after 10 minutes, at 60 degrees - after 2 minutes. At room temperature, virulence lasts up to 30 days, at -10 degrees 210-370 days. In the aquatic environment, viruses remain active for 24 hours, in an empty house - up to 9 days, with biothermal decomposition of manure, viable viral particles remain for about 2 weeks.
The death of viral particles occurs after 30-120 seconds in 1% sodium hydroxide solution, 5% phenol solution or 3% creosote solution. Premises in the presence of birds are disinfected with aerosol preparations based on quaternary ammonium derivatives.
epizootology
The most susceptible to the virus are young animals aged from 1 month to 1 year, however, adults also become ill. The main source of infection is sick chickens and latent virus carriers from among the ill livestock. Infection occurs "from beak to beak", the virus can be transmitted through water, feed, farm equipment, feed pests, dust, clothes and shoes of personnel. Outbreaks of the disease are widespread. The development of epizootics is facilitated by inadequate feeding of birds, increased humidity in rooms, poor ventilation, and crowding.
Vaccination with live vaccines is almost equivalent to a past disease, replenishment of the herd with vaccinated individuals almost always leads to an outbreak of ILT. The pathogen does not penetrate the eggs, but remains on the contaminated shell. Eggs of sick and recovered individuals are not subject to incubation and are suitable only for human consumption.
Since epizootics are caused by different strains of the virus, mortality varies greatly and reaches 75% in cases of lesions with highly aggressive strains. Due to the latent carriage of the virus, including the carriage of vaccine strains, it is quite difficult to remove the infection from the farm.
Outbreaks of the disease occur mainly in the off-season. ILT causes the greatest damage to large poultry farms and complexes. In addition to direct losses associated with the death and forced slaughter of sick birds, economic damage consists of the following positions:
On large farms where technological process put on stream, the infection can go into a stationary one. There is evidence that the virus is likely to spread by air within a radius of up to 10 km from the location of an ILT outbreak.
Pathogenesis
The causative agent affects the mucous membranes of the trachea and larynx; in chicks and young animals, the conjunctiva often becomes the entrance gate of infection.
Symptoms and features of the course
Outbreaks of the disease can occur at any time of the year, but the peak incidence occurs in autumn and spring. Significant fluctuations in temperature during this period weaken the immune system, and the respiratory tract is most vulnerable. The incubation period of ILT is from 1 to 30 days, on average - about 10. The duration of the incubation period depends on many factors, including the conditions of detention.
After the penetration of the infection into the thickness of the mucous membranes, rapid reproduction of the virus begins. This causes an acute inflammatory reaction of the serous-hemorrhagic type. Edema of the submucosal layer develops, the epithelium in the affected areas is intensively exfoliated. Possible aggravated course with the addition of secondary infections.
Clinical forms of pathology
Pathology has several clinical forms, which differ in the course and symptoms. Classic form - laryngotracheal. In sick birds, the neck swells noticeably, chickens breathe heavily with an open beak, stretch their necks, make croaking sounds, cough, wheeze, blood clots may be present in the coughing mucus. The laryngotracheal form is most often acute.
conjunctival form often chronic, affecting mainly chicks under the age of 15 days, but can occur at any age. There are signs of eye damage: mucus discharge from the eyes, photophobia, sticky eyelids. As the inflammatory process progresses, the palpebral fissure deforms and narrows. In the absence of treatment, clouding of the cornea occurs, the eyeballs often atrophy, and the ill chickens go blind. The clinically pronounced period lasts from several weeks to several months.
mixed form It is diagnosed if the airways and eyes are simultaneously inflamed. With such a development of events, any variant of the course is possible, including chronic. Flow atypical form ILT is erased, subclinical, the state of birds is closer to the usual virus carrier.
ILT flow types
There are four types of ILT flow:
- lightning fast or superacute;
- acute;
- subacute;
- chronic.
At hyperacute current the outbreak occurs suddenly, in 2-3 days it spreads to most of the livestock. The death of a part of the livestock occurs before the manifestation of the first clinical symptoms and loss of body weight. lightning current possible with laryngotracheal and mixed lesions, in which respiratory disorders are manifested. Sick birds stretch their necks, breathe with an open beak. The breath is bubbling, wheezing and gurgling are heard. In the respiratory tract, dead tissues and mucus form plugs that make breathing even more difficult, the birds cough. In the separating mucus, blood impurities are often present. Foamy mucus is discharged from the nostrils and eyes. Chickens die from suffocation.
The acute course differs from the fulminant one by a longer increase in symptoms. As a rule, single individuals fall ill first, the disease takes on the character of an epizootic within several days, affecting 50-80% of the flock, and mortality in acute ILT is up to 60%. Acute development is characteristic of laryngotracheal and mixed forms of infection. Accordingly, the symptoms of damage to the respiratory system predominate in the clinical picture.
Acute forms of the flow can turn into subacute, sometimes subacute course happens to be original. Clinical manifestations increase slowly, over several days, sick chickens cough, breathing is difficult, there are discharges from the nose, often from the eyes. Mortality - up to 30% with a general incidence of up to 60%.
At chronic course morbidity - about 2%, no more than 10% of affected birds die, with timely intensive treatment - 1-2%. Sick chicks grow poorly, adults lose weight, cough. There is discharge from the nose and eyes. A week after the onset of the first symptoms, egg production decreases by half, and ILT does not affect the structure and quality of eggs.
One of the first signs of damage to the respiratory system is a change in the rhythm of breathing. If the bird's tail rises and falls to the beat of breathing, this is already a reason for its isolation from the herd. Squeaks, wheezing, gurgling sounds and other obvious changes in the early stages of the disease increase in the evening. Soreness with inflammation of the larynx makes it difficult to swallow, chickens do not eat well or refuse to feed at all.
If the trachea of a supposedly sick individual is slightly squeezed, a cough begins. On the surface of the larynx, signs of inflammation are expressed: redness, swelling, pinpoint hemorrhages, the lumen is partially blocked by accumulations of mucus and curdled lumps of dead cells. The comb and earrings take on a bluish tint.
Diagnostics
On the basis of epizootological features, clinical symptoms and pathological changes in the affected organs and tissues, it is not always possible to establish an accurate diagnosis. Final Diagnosis can be established only after the isolation and study of the pathogen. Pathological material to identify the nature of the pathogen are:
- corpses of dead chickens;
- live chickens with a pronounced clinical form of the disease;
- scrapings and smears from inflamed mucous membranes;
- mucus from the eyes and nose.
The infectious agent is isolated by seeding on cell culture or chorion-allantoic membranes of chicken embryos. A series of virus-specific serological tests and histological studies of the pathological material are being carried out.
Pathological changes
At autopsy, severe swelling and redness of the tracheal mucosa are detected, the lumen can be blocked by a blood clot or a curdled plug. In the absence of secondary bacterial infections, the air sacs and lungs are weakly affected.
ILT is differentiated from chronic pasteurellosis, Newcastle disease, respiratory mycoplasmosis, hemophilia and infectious bronchitis.
Treatment
There is no effective antiviral treatment that completely destroys the ILT virus. If a disease is detected, all sick and suspicious birds are isolated. The isolated part of the livestock is slaughtered, the carcasses are subject to technical disposal. Treatment is aimed at eliminating symptoms and preventing secondary infections. Iodine preparations and antibiotics are used. Birds are given blue iodine with food or inhaled with triethylene glycol or aluminum iodide.
For inhalation, powdered crystalline iodine, ammonium chloride and aluminum powder are mixed in equal proportions and placed in metal containers (glasses). The reaction proceeds violently, with the release of a large amount of heat, so you should take care of safety. Prepared glasses are placed around the poultry house and 2 ml of water are added per 10 g of the mixture. The calculation of the required amount of the mixture is based on the volume of the room: 1.2 g is enough to process 1 cubic meter. The bird is locked up until the end of the reaction.
Since it is rather difficult to obtain crystalline iodine, iodine monochloride can be used. The reagent is mixed with powdered aluminum (silver paint) in a ratio of 10 ml: 1 g, respectively. Mixing is done in a ceramic bowl. The dishes with the fuming reaction mixture are placed in the chicken house, the door is closed. The reaction lasts about 10 minutes. The specified amount is enough to process a room up to 10 square meters. Inhalation should be carried out several times, with an interval of 2-3 days.
Additionally, all birds are given antibiotics - tetracycline derivatives or analogues of the drug "Tylosin". An alternative option is complex preparations containing both active component, for example, "B-septim". It is recommended to use in combination with trivitamin and furazolidone. The drug is given with food or used for drinking, depending on the form of release and manufacturer's recommendations. Dioxidine or nigras is sprayed indoors.
Control measures
Measures to combat any highly contagious disease are divided into two groups: preventive, aimed at preventing the pathogen from entering the farm, and emergency, to eliminate the outbreak of the disease.
Prevention
Preventive measures are divided into specific and non-specific. Specific measures include vaccination of birds using live and fetal preparations. Since the effect of vaccination may be unexpected, it is recommended in extreme cases.
Non-specific prevention of infectious diseases, including ILT, includes, first of all, keeping poultry in proper sanitary conditions, and these are:
- regular aerosol disinfection of poultry houses in the presence of birds;
- separate keeping of birds of different ages;
- full feeding with high-quality feed;
- proper ventilation of the poultry house;
- prevention of crowding of birds;
- regular inspection of the bird;
- isolation of all birds with suspicious symptoms, further examination and appropriate treatment.
The care and sanitary condition of the poultry house is especially important when the chickens are cage-free. When birds are controlled, the risk of ILT outbreaks is reduced. Purchase hatching eggs, chicks or adult bird to replenish commodity and breeding herds follows in farms that are free from ILT.
Specific prophylaxis
In the Russian Federation, a dry vaccine developed at TsNIIPP, as well as a live vaccine from the VNIIBP strain, is mainly used for immunization of poultry. Vaccination is carried out by rubbing the drug into the upper fornix of the cloaca, instillation into the conjunctival sac or aerosol. When rubbed into the cloaca, immunization occurs within 7-10 days, resistance to the disease remains sufficient for the production use of immunized individuals. The use of the vaccine in the form of an aerosol gives the desired effect on the 4-5th day after vaccination, immunity lasts for about a year. The use of an aerosol in the presence of mycoplasma infection on the farm can cause an outbreak.
The cloacal method of vaccination is very laborious and is not always feasible under conditions large farm. With aerosol vaccination, there is a risk of overdose and complications.
Outbreak control
ILT is especially dangerous diseases and the detection of cases of the disease is the basis for the introduction of quarantine with appropriate restrictions for the holding or zone in which it was found. According to safety requirements, during the quarantine period, any regrouping of birds within a dysfunctional farm is stopped. Requirements for compliance with non-specific preventive measures become tougher. The purchase of hatching eggs and chicks is temporarily prohibited, regardless of the status of the supplying farm.
Also temporarily prohibited:
- use of eggs from a dysfunctional flock for incubation;
- movement of feed, inventory, as well as any other equipment within the farm and export outside it;
- storage of eggs from infection carriers in a common egg store.
During quarantine, outsiders are not allowed on the farm, each poultry house is assigned service staff. All farm workers must be provided with overalls and safety shoes, which should be put on before entering the disaster area and removed when leaving. Clothing and shoes after each use must be disinfected according to the appropriate scheme.
The sale of eggs in retail chains is allowed only after preliminary disinfection. Deliveries of products from a dysfunctional economy are limited by the region.
Eggs intended for incubation are pre-disinfected. The first disinfection is carried out within the first two hours after demolition. Reprocessing is carried out after packaging, immediately before export or in the hatchery, immediately after delivery. After the end of the pre-hatching sorting, the third processing is carried out. Disinfection completes the cycle of preventive treatment after 6 hours of incubation.
For incubation, eggs are taken from healthy herds, the chicks are intended only for the needs of the economy. Restrictions on the importation of eggs for incubation and chicks do not apply to poultry houses where no cases of ILT have been detected. Poultry from safe poultry houses, intended for slaughter, can be taken out to processing plants and scored directly on their facilities. The slaughtered bird is gutted completely, the upper respiratory tract, organs and parts of the carcass with signs of pathological changes are to be disposed of.
Regardless of the presence of visible signs of the disease, poultry carcasses from a dysfunctional farm are not allowed to be sold in retail chains in a chilled and frozen form. Meat can only be used as a raw material for the manufacture of minced or canned products.
When the first case of ILT is detected in a previously prosperous farm, all birds from the problematic branch are slaughtered and disposed of in as soon as possible. The vacated premises are properly decontaminated. At the same time, all suspicious and weakened chickens in other poultry houses are culled. Clinically healthy stock should be vaccinated. Slaughter is carried out at a sanitary slaughterhouse, in the presence of a veterinary specialist. After completion of work, the premises and equipment of the sanitary slaughterhouse are disinfected.
The conditions for keeping clinically healthy livestock should be improved, the use of anti-stress feed additives is recommended. To prevent the transmission of the virus between poultry houses, service personnel are assigned to each branch of the farm for the quarantine period. All current work are carried out only in sterile overalls and safety shoes, the movement of personnel between poultry houses and the admission of outsiders are prohibited until the end of quarantine.
Forced and planned slaughter with a registered outbreak of the disease is carried out within 48 hours. If it is technically impossible to comply with this requirement on the basis of the farm, the clinically healthy part of the poultry population, with the permission of the relevant services, is exported to processing enterprises.
Feather and down can only be used after disinfection. For disinfection, the pen is treated with hot water or formalin solution. An air disinfection method is also used, in which a dry feather is kept for 20 minutes in disinfection chambers at a temperature of 90 degrees. Released containers, boxes and all other containers after the transportation of live poultry or any other types of products are also sent for disinfection.
On the territory of the farm during the quarantine period, cleaning is carried out with subsequent disinfection of the territory, all premises, including utility and technical, inventory and equipment. Disinfection is carried out in hatcheries, processed and all vehicles. The complex of preventive measures includes the destruction of insects and mouse-like rodents - possible mechanical carriers of infection.
Mouse-like rodents - mechanical carriers of the virus
Litter and litter are taken to specially equipped litter storage facilities, where biothermal disinfection is carried out.
Quarantine restrictions are removed after 2 months after the last case of stamping out of a clinically ill or suspicious bird and a set of appropriate veterinary and sanitary measures has been taken. Restrictions on the export of hatching eggs and poultry are removed no earlier than six months after the outbreak has been eliminated.
Video - Prevention of viral diseases of chickens
Infectious laryngotracheitis (ILP) is an acute infectious respiratory disease of chicken birds characterized by catarrhal-hemorrhagic inflammation of the mucous membranes of the trachea, nasal cavity, conjunctiva and accompanied by shortness of breath, wheezing and coughing.
Historical reference. The disease was first described in 1925. in the US by May and Titsler called tracheolaryngitis. For a long time infectious laryngoracheitis of birds was not differentiated from infectious bronchitis.
Later, Bigs, Silk and Hawn proved the independence of these two diseases, and from 1931 the disease began to be called "infectious laryngotracheitis".
In the USSR, this disease was established in 1932. R.T. Batakov. In 1951
S.T. Shchennikov prepared a vaccine on chicken embryos.
Infectious laryngotracheitis of birds is common in the USA, Canada, South America, Europe, Africa, Australia, and Asia. In Russia, ILP is registered mainly in farms with industrial production of poultry.
Economic damage with ILP, it consists of poultry waste, mortality reaches 15-50%, a decrease in egg production in ill and recovered laying hens by 10-30%, weight gain. The cost of measures to stop the infection. The premature culling of a sick bird causes great damage.
Etiology. The causative agent of ILP is a virus that belongs to the Herpesviridae family. The virus is found in large quantities in the exudate and epithelial tissues of the upper respiratory tract, in a smaller amount it can be found in the liver and spleen. The data on the size of the virus are contradictory: some researchers consider them from 30 to 100nµ, others from 150 to 240nµ. Virions are spherical in shape. Virions have three structural components: a core (nucleoid), a capsid with capsomeres, and an envelope. The particle size depends on the location of the virus, for example, in the cytoplasm it is larger than in the nucleus of the affected cell.
Viruses pass through Berkefeld W and N filters, Seitz E.K. and membrane ultrafilters with pores from 0.7 to 0.9nµ. Pathogen I.L.P. is constantly found in tracheal mucus, exudate of the larynx, conjunctiva, less often in the blood, spleen and liver of sick chickens. The serum of recovered ILP contains specific virus-neutralizing antibodies. Researchers distinguish between virulent and weakly virulent viral strains that lack antigenic differences.
The virus is stable in the external environment, especially at sub-zero temperatures. In frozen carcasses, the virus persists for more than 19 months, in corpses buried in the ground in summer to a depth of 120 cm - up to 47 days, in corpses on the surface of the earth (April-May) - over 30 days, dried - 359 days. At a temperature of 37 ° C on the shell of eggs, it dies after 12 hours, when heated to 55 ° C - after 2 hours, when boiled - immediately. In the poultry house, the virus persists for no more than 6-9 days. sunlight kills the virus after 7 hours. The virus is not resistant to the action of disinfectants, 3% sodium hydroxide solution and 3% cresol solution inactivate it after 30 seconds.
epidemiological data. Under natural conditions, to the I.L.K. chickens, pheasants, peacocks and turkeys are susceptible. Young chickens aged 5 months to a year are more susceptible, but chickens from 20-35 days of age can get sick.
I.L.K. some seasonality is characteristic, which is associated with changes in weather conditions, low temperature, high humidity in the premises and the deterioration of bird keeping in winter in household plots and peasant farms. Additionally, low temperatures contribute to a longer preservation of the pathogen in the external environment.
The disease in young hens and chickens occurs after the transfer of birds to other rooms with more worse conditions content (high humidity, insufficient ventilation, inadequate feeding, etc.).
Chicks hatched from full-fledged hatching eggs are resistant to I.L.C. in the first days of life.
In dysfunctional large poultry farms with a flow system of poultry rearing, the disease often becomes stationary. The stationarity of the disease in the farm is explained by the long-term virus carrier in a sick bird (up to two years). Virus carrying in birds vaccinated with live vaccines lasts at least 90 days.
The nature of the course of ILC is directly affected by the conditions of keeping and feeding the birds by the time the infection enters the poultry house: dampness in the room, poor ventilation, overcrowding, unbalanced feeding rations.
Epizootic strains of viruses differ in virulent properties, the degree of which can vary significantly.
The main source of infection in the farm is a sick bird and virus carriers. Transmission factors are food, water, objects, shoes and clothes contaminated with secretions of a sick bird, etc. Infection occurs through the air. A sick bird, when coughing, throws into the air small droplets of exudate containing the virus. wild bird, rats can be mechanical carriers of the disease.
If in an infected I.L.K. the flock does not introduce susceptible birds. Then at good conditions feeding and keeping the spread of the disease can stop after 2-4 weeks.
Pathogenesis. After entering the damaged mucous membranes of the larynx, trachea, cloaca, the virus penetrates the epithelial cells with the formation of intranuclear inclusions and causes an acute inflammatory process. The virus, having a tropism for the epithelial tissues of the respiratory tract, begins to actively multiply in them, causing edema and lymphocytic infiltration. In the initial stage of the disease in the lumen of the trachea, we find a mucous exudate, later, as a result of hemorrhages, blood and fibrin are mixed with the exudate. From the epithelial tissues, the virus spreads through the bloodstream to all organs of the bird. However, pathological changes in them usually do not occur. With laryngotracheitis, viremia is short-lived, the virus long time remains in the epithelial tissues of the trachea and larynx.
The formation of caseous plugs in the lumen of the trachea indicates the accession to the main process of opportunistic microflora. In such cases, isolation of the virus can be difficult. Cellular detritus, fibrin and blood cells form a clot that clogs the lumen of the trachea and causes clinical symptoms of suffocation and death of the bird.
Symptoms and course of the disease. The incubation period, depending on the virulence and amount of the virus that has entered the body, as well as on the resistance of the bird to the disease, ranges from 2 to 30 days. The first clinical symptoms of the disease in birds when the virus enters the intratracheal route appear after 3-7 days.
The course of the disease with I.L.P. may be acute, subacute, chronic and asymptomatic. At the same time, three forms of the disease are distinguished in a sick bird: laryngo-tracheal, conjunctival and atypical.
In case of acute of the laryngo-tracheal form, as a rule, individual chickens fall ill at first, and after 7-10 days, the whole bird of the disadvantaged group. In a sick bird, we note general oppression, lethargy; appetite disappears, they refuse to feed, the bird becomes inactive, sits with its eyes closed. When carefully listening to a calmly sitting bird in the evening, we hear a variety of whistling, croaking and wheezing sounds. Blockage of the larynx, trachea with exudate leads to respiratory failure. The bird breathes through an open beak, the act of inhalation and exhalation is difficult. When carrying out palpation in the larynx and tracheal tube, it causes coughing fits in the bird. The bird coughs up exudate, which sometimes contains an admixture of blood. When examining the open beak, hyperemia and swelling of the mucous membrane of the larynx and trachea are noticeable, sometimes with hemorrhages. In protracted cases, cheesy-fibrinous deposits accumulate around the larynx. In a sick bird, egg production stops. Mortality in acute laryngotracheitis is often 10-60%, depending on the adverse factors of feeding and maintenance.
Subacute course I.L.P. lasts 2-3 weeks, clinical signs are less pronounced. The bird recovers or the disease becomes chronic (over a month) and is characterized by periodic improvement in the condition of the bird. The bird has a cough, shortness of breath, anemic crest and wattles, when examining the pharynx and larynx, fibrinous, easily removable grayish overlays are found, oviposition is reduced.
conjunctival form a disease that usually proceeds chronically more often affects chickens with an intensive in-line rearing system, when over-infection of birds of different ages occurs. At the beginning, individual chickens of 10-15 days of age fall ill, and later the entire batch of poultry is affected. The main clinical signs are hyperemia of the mucous membranes of the eye, deformation of the palpebral fissure (narrowing of the palpebral fissure, protrusion of the 3rd century in the inner corner of the eye and sinusitis), eyelid edema, photophobia, lacrimation. During this period of the disease, the body temperature of chickens is increased by 1-2 °. The secreted exudate glues the eyelids of the eyes, hemorrhages are noticeable on the mucous membrane of the conjunctiva, fibrinous masses accumulate under the third eyelid, keratitis and panophthalmia occur with loss of vision. The process involves the infraorbital sinus, the mucous membranes of the nasal cavity.
conjunctival form infectious laryngotracheitis lasts from 20 days to 2-3 months and leads to the exhaustion of chickens and their increased rejection. This form disease can affect 5-90% of chickens up to 60 days of age. The disease is most severe when poultry is kept in rooms with high humidity and high ammonia content.
Atypical form detected by serological studies of the blood serum of birds. Often infectious laryngotracheitis occurs in association with other infections, such as respiratory mycoplasmosis, colisepticemia.
Pathological changes. In the laryngo-tracheal form, changes are found in the larynx and trachea, the mucous membrane of which is highly hyperemic, edematous, with small hemorrhages. The lumen of the trachea contains different amount mucous, serous or bloody exudate. With a long course in the lumen of the larynx, we find a caseous plug, often clogging the entire lumen. On the mucous membrane of the oral cavity on one or both sides of the root of the tongue and on its frenulum, we sometimes find caseous-fibrinous, small, easily removable plaques; less often - caseous foci in the lungs. Sometimes we find catarrhal-hemorrhagic inflammation of the cloaca, less often individual sections of the small intestines. In the Fabrician bag, a compacted curd-purulent mass is often observed. In the conjunctival form, the mucous membrane of the eyelids of one or both eyes is hyperemic, edematous, in some the cornea and eyeball are affected. In the early stages of I.L.P. histological examination of epithelial cells of the affected tracheal mucosa reveals characteristic intranuclear inclusions (acidophilic bodies), cell infiltration and desquamation of cells of the tracheal mucosa.
Diagnosis. We put it on the basis of epizootological, clinical, pathoanatomical data, as well as the results of laboratory studies (detection of intranuclear inclusions in the tracheal epithelium, the virus in the same place using fluorescent antibodies, RDP, RN). In the atypical course of the disease, laboratory research. After exclusion of bacterial infections, a bioassay is placed, a virus is isolated, a neutralization reaction is performed on embryos, a double diffusion precipitation reaction in agar gel, histosections are examined for the presence of intranuclear inclusions of a rounded or sausage-shaped shape, surrounded by clearly visible rims.
If a disease of birds with ILP is suspected, a clinically ill bird in the initial stage of the disease in the amount of 4-5 heads and fresh corpses are sent to the veterinary laboratory for examination.
Differential Diagnosis. I.L.P. must be distinguished from, and, contagious rhinitis,.
Pseudoplague of birds is characterized by an epizootic course, a characteristic lesion (ring of hemorrhages) of the mucous membrane of the glandular stomach, and ulcers on the intestinal mucosa.
Respiratory mycoplasmosis spreads slowly, affects the air sacs, and deaths are rare.
To exclude smallpox, the bird is clinically examined for the presence of smallpox lesions. The diphtheroid and conjunctival forms of smallpox, due to the similarity of clinical symptoms, can be differentiated by isolation and typing of the virus.
A-avitaminosis is characterized by easily removable plaque in the oral cavity, the absence of asthma attacks.
Immunity and immunization. After recovering from I.L.K. chickens acquire long-term immunity to subsequent infection. The mechanism of its formation is determined by cellular and humoral factors. Antibodies after infection appear after 14-20 days and remain in the blood serum for 2-3 months. The duration of immunity is 5-7 months. For immunization, naturally weakened and attenuated strains are used. Currently in Russia and countries customs union VNIIBBP and VNIIVViM vaccines are used. These vaccines are used by rubbing into the mucous membrane of the cloaca, instillation into the conjunctiva and aerosolized. When carrying out aerosol vaccination, immunity develops after 4-5 days and lasts up to a year. In poultry farms, the embryo-virus-vaccine from the clone NT of the TsNIIPP strain is widely used, which is currently less reactogenic.
Treatment. At the moment, there are no specific effective therapeutic agents for ILC. In order to reduce the loss of poultry and prevent the decline in egg production, antibiotics are used in combination with furozolidone and trivitamin, dioxidine (indoors), nigras (in the form of an aerosol).
Prevention and control measures. For the prevention of I.L.K. poultry owners must strictly implement measures to protect the economy from the introduction of pathogens of infectious diseases. Accomplishment of your farm with eggs intended for incubation and one-day-old chicks should be carried out only from farms that are safe in terms of ILC.
It is necessary to carry out veterinary and sanitary measures for the proper care, maintenance and feeding of the bird, especially in the case of cage-free keeping. Disinfect indoor air in the presence of birds using drugs that contribute to the partial inactivation of the virus and bacterial microflora in the upper respiratory tract. It is necessary to keep the bird separately depending on age. Unauthorized persons should not be allowed into the territory of the farms. When establishing the disease of birds with laryngotracheitis in accordance with the order of the Ministry of Agriculture of the Russian Federation No. 476 of December 19, 2011 "On approval of the list of contagious, including especially dangerous animal diseases for which restrictive measures (quarantine) can be established" by the decision of the Governor of the region on the economy (farm, poultry house) impose quarantine and impose restrictions on it. Activities in a dysfunctional farm are carried out in accordance with the temporary instruction on measures to prevent and eliminate the disease of birds with infectious laryngotracheitis. Approved by the Main Directorate of Veterinary Medicine of the USSR Gosagroprom on April 1, 1983. Under the terms of quarantine, it is prohibited:
- movement of poultry within the holding (farms, branches, zones) during the outbreak of the disease;
- import to a dysfunctional economy (farm, branch, zone) and export from it of birds of all ages;
- export of hatching eggs to other farms;
- use of eggs from dysfunctional poultry houses for incubation within the farm;
- export of feed, equipment and inventory from disadvantaged industrial premises and from the territory of a disadvantaged economy (farms, departments, zones);
- importation and storage of eggs received in a dysfunctional department, zone, to the egg storage of the farm;
- the entrance to the territory of a dysfunctional economy and the exit of people from it without complete sanitization and change of clothes and shoes.
During the period of trouble of the economy it is allowed:
- export of food eggs from a dysfunctional department (zone, farm) after disinfection in trading network within the region;
- incubation of eggs for on-farm purposes from birds of safe poultry houses after aerosol disinfection with a formaldehyde solution according to the scheme: the first time - no later than 1.5-2 hours after laying, the second - packed in containers in a special vehicle or the disinfection chamber of the hatchery, the third - after sorting before laying in the incubator , the fourth - 6 hours after the start of incubation;
- delivery of hatching eggs and day-old chicks to a safe department, farm zone;
- in the absence of the economy slaughterhouse export to poultry meat processing enterprises of birds of safe poultry houses subject to planned slaughter, with the permission of the state veterinary supervision authorities of the region (krai, republic that does not have a regional division).
When ILP occurs for the first time on the farm, in order to prevent the spread of the disease, all birds in a dysfunctional poultry house are killed. At the same time, all necessary veterinary and sanitary measures are taken to ensure the destruction of the pathogen in the external environment.
When the disease spreads to other poultry houses, a thorough culling is carried out and sick and weak birds are slaughtered at the sanitary slaughterhouse of the economy (farms, departments, zones).
All clinically healthy birds are immunized with the ILP vaccine in accordance with the instructions for its use.
The farm is improving the feeding and keeping of birds, introducing anti-stress drugs (supplements) into the diet.
Each poultry house is assigned attendants, who are provided with overalls, special footwear, and disinfectants.
Poultry is slaughtered in compliance with veterinary and sanitary rules under the supervision of a veterinarian, followed by disinfection of slaughter sites, inventory and equipment.
If it is necessary to slaughter a large batch of poultry from a dysfunctional poultry house and it is impossible to slaughter it on the farm within 2 days with the permission of the regional veterinary department, etc. it is allowed to export clinically healthy poultry to meat processing enterprises in compliance with the relevant veterinary and sanitary rules.
Fluff and feathers obtained from the slaughter of birds from dysfunctional poultry houses are disinfected in accordance with clause 3.6. instructions.
Containers and boxes after transporting poultry for slaughter, meat containers, as well as containers, cardboard pads, boxes and other containers used for transporting eggs are subject to mandatory cleaning and disinfection.
During the period of trouble, the farms (departments) according to the ILC conduct a thorough mechanical cleaning, as well as the current and final disinfection of dysfunctional poultry houses, hatcheries, utility rooms, inventory and equipment, production areas, means of transport and other objects, as well as disinfestation and deratization in the manner and terms provided for current Instruction for veterinary disinfection, disinvasion, disinfestation and deratization.
Litter and deep litter are taken to the litter storage facility for biothermal disinfection.
Restrictions on ILC in the farm (department, zone) are removed 2 months after the last case of slaughtering a sick and recovered bird and carrying out final veterinary and sanitary measures.
Laryngotracheitis in chickens is a viral disease that affects the lining of the larynx and trachea. Additional symptoms are the occurrence of damage to the conjunctiva of the eye and nasal mucosa. With untimely treatment, a significant loss of livestock is observed.
What is laryngotracheitis in chickens
This disease is infectious and quite dangerous. It occurs due to the entry of viruses into the body. The virus is stable, after passing the incubation period it lives for several years in a fairly active state. Not only domestic chickens can suffer from laryngotracheitis, but also another Domestic bird. Larengotracheitis has two main forms: acute and superacute.
The acute course of this disease brings up to 15% mortality of livestock, over acute can be up to 60% of the case. Sometimes this disease can occur in a chronic form. The most susceptible to this disease are young animals aged from 4 weeks to 8 months. This disease is dangerous to humans, the virus can be transmitted through contact with a sick bird.
Signs of infection with laryngotracheitis from chickens in humans
The larynx, trachea, and also the skin of the hands are affected, bronchitis develops. This disease is especially prevalent during periods of large temperature fluctuations between seasons. insufficient compliance cleanliness in the chicken coop and with a low immune system in birds. A bird that has been ill with laryngotracheitis is immune and is no longer predisposed to this disease. But such a bird can be a carrier. The main route of transmission of the disease is airborne.
Symptoms of laryngotracheitis in chickens
Laryngotracheitis occurs in 2 forms: acute and super-acute, it must be understood that the super-acute form is formed only in those farms where the disease was previously detected and they are considered unfavorable for this disease. In the first days, infection occurs up to 80% of the total livestock. The main symptom of laryngotracheitis in chickens is the appearance of very difficult breathing difficulties. Further coughing, choking, expectoration is observed. A bird that has been ill with this disease can wheeze for a long time and suffer from inflammation of the conjunctiva of the eye.
Symptoms of over-acute course of laryngotracheitis in chickens
First, attacks of suffocation appear, head shaking, a cough appears with bloody and other secretions, the larynx swells, cottage cheese discharge appears on the mucous membrane, appetite disappears, egg laying decreases, severe wheezing occurs.
Symptoms of an acute course of laryngotracheitis in chickens
In the acute form of the course, the respiratory organs are affected, spread throughout the livestock occurs within a week. If there is a rapid detection of the disease and the correct treatment is carried out, then the mortality rate is low, usually does not exceed 20%. Signs indicating laryngotracheitis are a decrease in appetite, inactivity, a lethargic state, when breathing in birds, hoarseness and whistling are heard, a cough is observed, when the larynx swells, there are cottage cheese discharges, the conjunctiva swells. Sometimes, with untimely treatment, the bird may lose its sight.
How to treat laryngotracheitis in chickens
With this disease, the speed of treatment is important. For this disease in the poultry industry, there is not yet the necessary drug for treatment, but broad-spectrum antibiotics that reduce the activity of the virus can be used. An antibiotic such as biomycin significantly increases the safety of the livestock; when using these drugs, it should be remembered that they are given in conjunction with vitamins. It is better to prevent this disease, so prevention is necessary, which includes a balanced nutritional diet and compliance with sanitary and hygienic standards in the chicken coop. Also, in the room where the bird is kept, periodic disinfection is carried out using a mixture of chlorine and turpentine. At large poultry enterprises, a special vaccine against laryngotracheitis is used as a prophylaxis.
Infectious laryngotracheitis of birds affects chickens, turkeys and pheasants. It is characterized by an acute course and hemorrhagic inflammation of the mucous membrane of the trachea, larynx, sometimes the conjunctiva of the eyes and death of the bird from suffocation.
Most often, bird laryngotracheitis affects young animals from the age of 1 month, but adult birds also suffer greatly from this disease. Therefore, we suggest that you talk about the symptoms of laryngotracheitis in chickens and how to treat bird 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 elevated temperatures: at a temperature of 55 0 C it dies after 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 the litter during biothermal treatment it is destroyed after 10-15 days.
Avian 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 poultry, 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 spread with infected feed, equipment, water, dust. In addition, the carriers of the virus can be beetles - pests of feed.
Mortality from infectious avian laryngotracheitis is 2-75%. Since ill chickens, guinea fowls, pheasants and turkeys are carriers of 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 birds from virus carriers of vaccine strains and their further reversion to virulent strains.
Infectious laryngotracheitis of chickens: symptoms
This virus multiplies in the epithelial cells of the larynx and trachea, causing acute serous-hemorrhagic inflammation with the phenomena of "peeling" 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 plaques develop on the affected mucous membranes, epithelial degeneration is observed.
The incubation period for infectious laryngotracheitis in birds lasts from 3 to 15 days. There are two main forms:
- Laryngotracheal - classical 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 laryngotracheitis of birds can occur in three clinical forms:
- acute form. It is accompanied by a sudden appearance and lightning 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 its neck, and shortness of breath is not heard. At the same time, the chickens cough, wheeze, trying to remove the obstruction from the trachea. On the walls and floor of the chicken coop, you can see blood clots that the bird coughs up. At autopsy, the main changes are observed in the upper respiratory tract and are characterized by hemorrhagic tracheitis, mucous rhinitis, and layering of diphtheria films with an admixture of blood along the entire length of the trachea.
Typical symptom: hemorrhagic tracheitis (bleeding into the trachea) 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. Morbidity is also high, but mortality is somewhat lower - 10-30%. At autopsy of carcasses, pathoanatomical changes are less pronounced than in the acute form: in the trachea, in the area of the respiratory gap, hyperemia, swelling of the mucous membrane, small 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, formed as a result of laryngotracheitis - Chronic or moderate form . This form of infectious laryngotracheitis of chickens 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 suffocation. Chronic form bird laryngotracheitis is characterized by choking, coughing, discharge from the nose and beak. Outbreaks of a moderate form of infection can affect a large number of birds at the same time. Sometimes lesions develop in the form of sinusitis, conjunctivitis, serous tracheitis. An autopsy of the bird reveals diphtheria and necrotic plaques in the trachea, larynx, and oral cavity.
Infectious laryngotracheitis of chickens: treatment and prevention
For specific prophylaxis of poultry, the following drugs are used:
Virus vaccines "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. Vaccinate chickens at the threat of infection with laryngotracheitis not 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 laryngotracheitis of birds it is recommended to carry out blue iodine with food, as well as inhalation with aluminum iodide or triethylene glycol.
To do this, take a mixture of pounded iodine powder, ammonium chloride and aluminum powder, place it in metal glasses, which are evenly spaced around 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 1 cubic meter of space). At the same time, the bird is not released from the house while the reaction continues.
Our article provides a simplified, more realistic procedure for processing a room. 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. You can also find crystalline iodine in the tips, but they no longer sell it in pharmacies. Therefore, we take 10 ml of iodine monochloride (a yellow liquid with a pungent odor), and mix it in a ceramic dish with 1 gram of aluminum (you can take silver paint or an aluminum dart). As a result of the reaction, yellow smoke is emitted, the dishes are placed in a chicken coop and closed. 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 drink the chickens with an antibiotic as described in the prevention section.
In this case, it is best to take tetracycline antibiotics or preparations based on Tylosin. There are drugs that combine both active ingredients (for example, Bi-septim). The antibiotic should be given to all birds on the farm where there are chickens, pheasants, turkeys, guinea fowls sick with laryngotracheitis, or where there is a suspicion of this infection to protect the bird from possible complications. Antibiotics are drunk or given with food, depending on the manufacturer's recommendations.
However, when treating poultry, one should not take drugs that irritate the mucous membrane of the respiratory tract, such as formalin, turpentine chloride, etc.
Sick birds must be slaughtered and disposed of.
Tatyana Kuzmenko, member of the editorial board of the Sobcorrespondent of the online publication "AtmAgro. Agroindustrial Bulletin"
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 reference, distribution and economic damage. Infectious laryngotracheitis of birds was first reported in the United States in 1924.
In 1925, this disease was described by May and Titsler under the name tracheolaryngitis. Other American researchers (1925-1930) described it under the name infectious bronchitis. Later, the independence of these two diseases was proved, and a histological examination showed that with this disease, the larynx and trachea are mainly affected. The Special Committee on Diseases of Birds in the USA (1931) proposed that this disease be called infectious laryngotracheitis, which persists to this day. This disease covered almost all US states, and then spread to Europe, Australia, New Zealand and Asia.
In the USSR, infectious laryngotracheitis of birds was first described by R. T. Botakov in 1932 under the name of infectious bronchitis.
Later, A. P. Kiur-Muratov and K. V. Pachenko (1934), S. A. Polyakova (1950), T. S. Schennikov 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 from this disease consists of losses as a result of the death of a sick bird, 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 persists for up to 86 days at a temperature of 2-4 ° C, indoors - up to 30 days, on the egg shell - 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 retains its virulence 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 seconds.
The strains of the virus circulating in the country are antigenically related, but differ from each other in virulence and ability to be cultivated in cultures of chicken fibroblasts. Some strains have hemagglutinating properties.
epidemiological data. Under natural conditions, only domestic birds are susceptible to infectious laryngotracheitis, in particular chickens of all ages and sometimes pheasants, but in laboratory conditions it is possible to infect turkeys, ducks, but without showing symptoms of the disease.
Chicks between the ages of 3 and 9 months are susceptible to infection. Month old ILT chicks do not get sick, despite the fact that the virus grows on chick embryos, day old chicks are free from the disease.
The main source of infection is a sick and recovered bird.
The recovered birds are not susceptible to infection, but for a long time (up to 2 years) they are virus carriers and continue to shed the virus during external environment. Infected birds constitute a major and long-term source of the virus because, like all herpes viruses, an infected animal continues to be a carrier and sheds the virus throughout its life.
The main routes of transmission of the virus are aerogenic (airborne) and contact. The respiratory organs serve as the gates of infection. The virus is transmitted from a sick bird to a healthy one mainly through infected air. From a dysfunctional poultry house, the virus with air masses spreads over a long distance - up to 10 km. It is possible to transmit the virus with slaughter products, down and feathers, incubation waste, containers, bedding, feed.
With the contact route, the entire livestock is re-infected in a short period, especially in broiler poultry farms.
The infectious laryngotracheitis virus is not transovarially transmitted.
The disease spreads in all seasons of the year, but more often in summer and autumn. The disease often occurs when poultry is kept in damp, dusty, gassed, in cold and drafty rooms, with insufficient air exchange, excessive planting of birds in poultry houses and the presence of diseases.
Mortality of birds with ILT averages 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 up to 90.5-100%, in chickens - up to 96.2%. In the conjunctival form of ILT, the incidence is 5-87%.
A person can also get sick with infectious laryngotracheitis, but the disease occurs in mild form with a happy outcome.
Pathogenesis. The ILT virus, having penetrated into the upper respiratory tract, invades the epithelial cells of the mucous membranes of the larynx and trachea, and in some cases also other parts of the respiratory organs. In the affected cells of the epithelium, the nuclei rapidly multiply without dividing the cytoplasm. Soon there comes dystrophy of cells and their rejection into the lumen of the affected parts of the respiratory organs.
The reaction of the body 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, lung parenchyma and the wall of the air sacs, swelling 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, cell-infiltrative and proliferative reactions, desquamation of the respiratory epithelium and effusion of exudate in various parts of the respiratory system.
Subsequently, the ILT virus penetrates into the blood through damaged vessel walls, where it is detected as early as 24 hours after infection.
Sharp desquamative processes in 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 swelling of the own layer of the mucous membrane.
Increased vascular permeability, as well as their rupture due to mechanical causes (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) by caseous plugs leads to death birds as a result of asphyxia. 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 averages 4-10 days (with fluctuations from 2 to 30 days).
The course of infectious laryngotracheitis can be fulminant, acute,
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With a fulminant course, the disease begins suddenly and spreads rapidly throughout the herd within a few days.
The incidence rate is extremely high and so is the mortality rate - it can be 50-70% of the total number of sick birds. Some individuals rarely show clinical signs of the disease for a period of more than 2-3 days before death, some of them die without first appearing symptoms. It is rare to see a clear loss of body weight and often the bird with the highest body weight is found to be sick. Respiratory symptoms appear immediately, without visible signs. Obvious breathing difficulties are observed, the bird stretches its head and neck, closes or covers its eyes and takes a long breath. This is accompanied by gurgling and wheezing. There is a spasmodic cough, with the head shaking violently in an attempt to remove obstructions in the trachea. When coughing, blood clots and mucus with blood inclusions are released, they 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.
In the subacute course in most birds, the disease progresses more slowly. Difficulty breathing, coughing, and other respiratory symptoms may last for several days before death. The incidence rate is still high, but the mortality rate is lower, it can cover from 10% to 30% of the diseased birds. This form of the disease may predominate throughout the period or occur at the end of an extremely acute outbreak.
The laryngotracheal form of the disease can be observed with fulminant and acute course in the first 5-7 days. The bird heard 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 rhythm of breathing and asphyxia.
In a chronic course, the level of the disease in the herd can be 1-2%, but most of the sick birds invariably die from suffocation, sometimes after different periods of time, often after long ones. The main symptoms are: 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 the chronic course, the disease also manifests itself in the 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 in chickens, photophobia, lacrimation, gluing of the eyelids and deformation of the palpebral fissure are observed. Hemorrhages are visible on the mucous membrane of the eyes, accumulations of fibrinous mass are noticeable under the third eyelid, atrophy of the eyeball occurs.
In some birds, clouding and ulceration of the cornea are noted, accompanied by partial or complete loss of vision.
The conjunctival form lasts from 20 days to 2-3 months and leads to exhaustion and increased culling of the bird.
With a mixed form of the disease, signs of all forms appear, but it proceeds more severely, and, as a rule, ends in an unfavorable outcome.
The atypical form of the disease proceeds with blurred clinical signs.
pathological changes. With the laryngotracheal form, the main changes are found in the larynx and trachea. The lumen of these organs in some birds is filled with various 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 gap. Caseous plugs are usually easily separated from the mucous membrane. The mucous membrane itself is sharply hyperemic, unevenly thickened and riddled with numerous dotted and striped hemorrhages, especially in the larynx and upper trachea.
In some enzootics of infectious laryngotracheitis, the hemorrhagic focus 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 a gray-yellow color are found.
Similar changes in the lungs often develop in a large percentage of cases in chickens infected in the trachea. With 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 case of damage is diffusely or focally 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 with respiratory mycoplasmosis and infectious laryngotracheitis.
Of the other changes found at autopsy, some researchers note catarrhal enteritis, cloacitis, lesions of the Fabricius bag and spleen hyperplasia.
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.
In some enzootics, the vast majority of birds show serous conjunctivitis. In this case, the conjunctiva is hyperemic, edematous, sometimes with petechial hemorrhages. Some birds note swelling of the eyelids, especially the lower one. In some chickens and chickens, there is an accumulation of fibrinous-caseous masses, gluing of the eyelids, clouding 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 mucosa and submucosa. Sometimes swelling of the mucous membrane destroys its normal structure, which leads to the presence of perivascular hemorrhages. 3-5 days after infection, a continuous cellular infiltration of 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-shaped, or diplococcal in shape and occupy half of the cell nucleus. An uncolored zone is visible around the nuclear inclusion.
Immunity. The serum of birds that have recovered from infectious laryngotracheitis and hyperimmune birds contains specific virus-neutralizing antibodies. Recovered birds acquire strong immunity, which is transmitted 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.
To confirm the diagnosis, it is necessary to isolate the virus. The material for the study is fresh corpses, clinically sick birds (4-5 animals), exudate from the trachea, as well as scrapings of the affected mucous membrane of the larynx and trachea.
This is done in the following way:
Seeding of tracheal exudate on chorion-allantoic membranes;
Sowing on cell cultures;
RDP with tracheal exudate or with an infected chorion-allantoic membrane (CAO) using hyperimmune sera;
Detection of herpes viruses by electron microscopy: in tracheal exudate; growth at KhAO; immunofluorescence; Elisa using monoclonal antibodies to the ILT virus or ELISA;
Histological examination - detection of virus-specific intranuclear inclusions in the epithelium of the mucous membrane, Safe-Reed bodies.
Identification of the virus is carried out by a neutralization reaction (RN) on 10-11-day-old chicken embryos with specific antisera of chickens or rabbits.
differential diagnosis. Clinical signs of infectious laryngotracheitis are similar in some cases to other diseases of birds, therefore, when diagnosing them, it is necessary to exclude Newcastle disease, respiratory mycoplasmosis, infectious bronchitis, smallpox, contagious rhinitis, chronic pasteurellosis, hypovitaminosis A, ammonia blindness. Respiratory mycoplasmosis spreads slowly. Among the diseased, a large number of malnourished birds - "crackers", mostly young animals 5-7 months of age fall ill. At autopsy, lesions of the air sacs characteristic of respiratory mycoplasmosis - aerosacculitis - are found - their walls are thickened, opaque, covered with fibrinous films. Bird loss is negligible. When sowing on special nutrient media, the pathogen Mycoplasma gallicepticum is isolated from the air sacs and lungs; in retrospective diagnosis by enzyme immunoassay (ELISA), specific antibodies are isolated.
Infectious bronchitis of chickens is observed in them up to 30 days of age; proceeds mainly with the defeat of the bronchi, lungs and 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 comb, beards or diphtheria hard-to-remove deposits on the oral mucosa, as well as typical folliculitis that occurs after 4-8 days at the site of application of the virus-containing material. With an atypical form - for the isolation of the virus in chicken embryos.
The contagious rhinitis proceeds chronically; 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 bacteriological examination, the causative agent of infection Bact is isolated. hemophillus gallinarum.
Chronic pasteurellosis. When sowing on ordinary nutrient media, the causative agent of this infection is isolated Pasteurella multocida, which is pathogenic for laboratory animals (white mice, pigeons, rabbits).
Hypovitaminosis A. To exclude it in the conjunctival form, it is necessary to examine liver samples for the content of vitamin A. Both sick chickens and those without clinical signs of the disease, but in contact with the sick, are examined. 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 mucosa of the esophagus in the form of millet-like dense nodules, but histological studies and bioassay do not confirm infectious laryngotracheitis.
Ammonia blindness occurs when there is too much ammonia in poultry houses. When creating good ventilation, the disease quickly stops.
Treatment. Due to the fact that ILT causes significant economic damage to poultry farms, intensive searches are underway for drugs against this disease.
The most promising is the use of such drugs that can be used in any epizootic situation complicated by secondary infection.
Satisfactory results are obtained by using a 0.2% solution of sulfamethazan, 0.125% sulfazol with water for 2-6 days in a row, a solution of furacillin at a concentration of 1:5000 instead drinking water and furazolidone 0.04-0.06% of the daily diet for 2-6 days.
Iodinol has therapeutic and prophylactic properties against ILT. The drug is recommended to be added to water and feed at the rate of 0.25-0.5 ml per head per day. Particularly good results were noted when giving iodinol 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, irrigation of the mouth, nose and eyes with a 0.02% solution of gramicidin is recommended.
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 with daily dacha for 2-3 days.
A. A. Zakomyrdin, V. E. Zuev (1978) proposed iodotriethylene glycol, which is an oily liquid, to combat infectious laryngotracheitis. Aerosol of iodine-triethylene glycol disinfects the ambient air in the poultry house, has a virucidal and bactericidal effect.
Aerosol apply a 30% aqueous solution of glycosan.
At the Department of Poultry Farming and Diseases of Birds MVA (B. F. Bessarabov, 1992), a method for the use of the drug isatizon against viral laryngotracheitis has been developed. It is an oily liquid of dark yellow color, bitter taste, with a specific odor, contains metisazon mixed with dimethyl sulfoxide and polyethylene glycol-400. Isatizon is recommended for the prevention and treatment of infectious laryngotracheitis in chickens.
For aerosol disinfection of the air environment in the presence of a bird, Glutex, Virkon C.
specific prophylaxis. For prophylaxis, live embryonic vaccines are used, i.e., a virus grown on chicken embryos, and cultural ones - on cell culture. In poultry farms are used:
Dry virus vaccine from the VNIIBP strain against ILT; w embryovirus vaccine against ILT;
Dry liposomal virus vaccine from the VNIVIP strain against infectious avian laryngotracheitis;
Combined dry vaccine against Newcastle disease (ND) and infectious avian laryngotracheitis (ILT);
Virus vaccine from the clone "NT" of the TsNIIPP strain.
Virus vaccines are applied by aerosol, cloacal, ocular, enteral.
Immunity occurs on the 7-10th day and persists throughout the entire economic use of the bird. Vaccination is carried out only in disadvantaged farms, since in some cases up to 2% of chickens fall ill with ILT on the 8-15th day. Therefore, vaccinated chickens are reared 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 taken in accordance with the instructions.
In a dysfunctional economy. When a diagnosis of ILT is established, the farm is considered unfavorable and the following restrictions are introduced in it: it is not allowed to take poultry, feed, equipment and inventory out of the farm, and during an acute outbreak, move the bird inside the farm.
When ILT occurs in a separate poultry house, all the birds from it are sent to a sanitary slaughterhouse. Carry out a thorough mechanical cleaning and disinfection of a dysfunctional poultry house. Litter after treatment of the premises with disinfectant solutions is subjected to biothermal disinfection.
In farms that are unfavorable in terms of ILT, the conditions for keeping and feeding birds are improved. Birds of different age groups are placed in territorially isolated zones, with the necessary veterinary breaks.
Import of breeding eggs and day old chicks is allowed; export of eggs to the distribution network after disinfection, export of conditionally healthy poultry to meat processing plants, export to enterprises Catering carcasses obtained from the slaughter of conditionally healthy birds, export after disinfection of fluff and feathers to processing enterprises.
Completion of poultry houses and zones with healthy young animals of the same age is carried out at least 30 days after the acute course of the disease in other poultry houses of the economy.
Carefully observe inter-cycle preventive breaks with cleaning and disinfection of the premises.
Restrictions on a dysfunctional farm are removed 2 months after the last case of a case or slaughter of a sick bird, the final veterinary and sanitary measures and the absence of infectious laryngotracheitis virus isolation.
Export of birds to other farms to complete 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 help disinfect indoor air in the presence of birds and partially inactivate the virus in the upper respiratory tract, and immunize birds with vaccines.
