Basic overview

Avian Infectious Laryngotracheitis (AILT) is an acute, contact upper respiratory tract infection caused by the infectious laryngotracheitis virus. Characterized by dyspnea, coughing and coughing up blood-like exudates. Necropsy visible larynx, tracheal mucosal swelling, bleeding and erosion. In the early stage of disease cells can form nuclear inclusion bodies. The disease was first reported in the United States in 1925, is now throughout the world many chicken areas. The disease spread faster, higher mortality.

Pathogen of Avian Infectious Laryngotracheitis

Avian infectious laryngotracheitis pathogenic herpes virus type I, viral nucleic acid for the double-stranded DNA. The virus particles were spherical, for the twenty-sided three-dimensional symmetry, nucleocapsid by the 162 shell particles in the nucleus was scattered or crystalline arrangement. The virus is divided into two kinds of mature and immature virus, mature virus particles diameter 195 ~ 250nm. Mature particles have capsules, cystic surface of the fiber process. The immature viral particles have a diameter of about 100 nm.

The virus is mainly present in the tracheal tissue and exudate of diseased chickens. Liver, spleen and blood are rare.

The chick embryo inoculated 10 days old chick embryo chorioallantoic membrane, chick embryo 2 to 12 days after inoculation death, the disease inoculation of the first generation of chick embryos often do not die, with the chicken embryo in the following And the death time of chick embryo is shortened, and the death of chicken embryo is gradually and regularly. Death embryo small, chick embryo chorioallantoic membrane hyperplasia and necrosis, the formation of turbid scattered edge of the uplift, the center of the depression of the pock-like necrotic lesions. Usually 48h after the beginning of the emergence of poisoning, then gradually increased.

The virus can be easily proliferated in chicken embryo cells (chicken embryo hepatocytes, chick embryo kidney cells) and chicken kidney cells. After 4 to 6 hours after inoculation, cells can be swollen, nuclear chromatin and nucleolus become round, , 36 ~ 48h, can be multinucleated giant cells (syncytia), 12h after inoculation, inclusion bodies can be detected in the nucleus, 30 ~ 60h inclusion body of the highest density.

Infectious laryngotracheitis different virus strains, pathogenicity and antigenicity are different, is considered only one serotype. As the virulence of the virus strains on the different pathogenicity of chickens, to control the disease to bring some difficulties, often in the presence of groups of infected chicken, sick chicken can be infected more than 1 year.

Infectious laryngotracheitis virus on chicken and other commonly used experimental animals, red blood cells without agglutination.

The virus on ether, chloroform and other lipid solvents are sensitive. Resistance to the external environment is not strong. Heating 55 ℃ survived 10 ~ 15min. 37 ℃ survival 22 ~ 24h; in the death of chickens in the tracheal tissue of the virus, at 13 ~ 23 ℃ can survive 10 days. 37 ℃ 44h death; tracheal mucus in the virus, in direct sunlight 6 ~ 8h death, but in the dark room can survive 110 days; in the chorioallantoic membrane, at 25 ℃ by 5h was inactivated. Virus is dry environment can survive more than 1 year. In low temperature conditions, the survival time is long, such as -20 ℃ ~ -60 ℃, the long-term preservation of its virulence. Boil immediately to death. Veterinary commonly used disinfectant such as 3% to Sur, 1% caustic soda solution or 5% carbolic acid lmin can kill. Formaldehyde, peracetic acid and other disinfectant also has good disinfection effect.

Clinical symptoms

Natural infection <strong> incubation period </ strong> 6 to 12 days, 2 to 4 days after the artificial tracheal inoculation chickens to disease. The length of incubation period and the virulence of the virus.

Early onset, often several chickens died suddenly. Chicken nasal fluid initially, translucent, tears, accompanied by conjunctivitis, followed by the performance characteristics of the respiratory symptoms, respiratory rales issued when wet, coughing, wheezing, chicken crouched the ground or percussion , Each inspiratory head and neck forward, mouth, try to inhale the position, there are breath sounds. Severe cases, a high degree of dyspnea, cramps, cough, can cough up blood mucus, contaminated beak angle, face and head feathers. In the chicken coop walls, bedding, chicken cage, chicken back feathers or adjacent chicken body stained with bloodstains. If the secretions can not cough up the block, the chickens can suffocate to death. Chicken loss or loss of appetite, rapid weight loss, crested hair Hui: sometimes also excreted green manure. And finally died due to failure. Laying hens egg production decreased rapidly (up to 35%) or stop rehabilitation after 1 to 2 months to recover.

Course of disease: the most acute cases can be about 24 hours of death, most 5 to 10 days or longer, not dead by more than 8 to 10 days to recover, and some can become poisoned chicken.

Some less virulent strains cause morbidity, the epidemic is relatively mild, low incidence, mild symptoms, but listlessness, slow growth, reduced egg production, conjunctivitis, infraorbital sinusitis, rhinitis and bronchitis. Long course, long up to 1 month. Mortality is generally low (2%), most of the sick chickens can be resistant. If secondary bacterial infection and stress factors exist, the mortality rate will increase.

Control measures

There is no specific treatment. The incidence group of anti-bacterial drugs, to prevent secondary infection have a role. Symptomatic treatment of chickens to take, such as serving Niuhuangjiedu pills or laryngitis pills, or other Qingrejiedu throat in the liquid or in the drug, according to reports, there are certain benefits, can reduce the death.