Causes and Control methods of Infectious larynx and trachea in White-feathered broilers

Infectious laryngotracheitis is an acute respiratory infectious disease caused by herpesvirus. Infectious laryngotracheitis is characterized by dyspnea, coughing and exudation containing blood. Swelling, bleeding and erosion of the laryngeal and tracheal mucosa were observed during autopsy. In the early stage of the disease, the cells of the affected part could form intranuclear inclusion bodies. The disease spreads quickly and the mortality rate is high, which endangers the development of chicken industry. The disease has occurred and prevalent in some areas of our country.

1. Infectious laryngotracheitis virus mainly exists in tracheal tissues and exudates of diseased chickens. The resistance of the virus to the external environment is very weak. After heating 55C for 15 minutes and 37C for 22 minutes, the virus died immediately after boiling. Disinfect it with 3% Lysol or 1% caustic soda disinfectant and kill it in 1 minute.

2. Epidemic characteristics under natural conditions, infectious laryngotracheitis mainly affects chickens, and can be infected in all ages and breeds, but the symptoms of adult chickens are the most characteristic. Sick chickens and poisonous crowing after rehabilitation are the main sources of transmission, usually through respiratory tract and intraocular transmission. Bedding grass, feed, drinking water and utensils contaminated by respiratory organs and nasal secretions can become infectious agents. The activities of people and wild animals can also be spread mechanically. Breeding eggs can also spread. A small number of recovered chickens can carry the virus for as long as two years. Chicken crowding, poor ventilation, poor feeding management, lack of vitamins and parasite infection can promote the occurrence and spread of the disease. Once the disease spreads from person to person, it spreads quickly, and the infection rate can reach more than 90%. The mortality rate varies according to feeding conditions and the condition of the flock, ranging from about 5% to 50% to 70%.

3. The incubation period of clinical symptoms of infectious laryngotracheitis in Yan chicken was 12 days for natural infection and 4 days for artificial trachea inoculation. Diseased white-feathered broilers initially had nasal juice, translucent, tears and conjunctivitis, and then showed characteristic respiratory symptoms, that is, wet rales, coughing and wheezing when breathing. Sick chickens crouch on the ground or on the perch. Every time you inhale, the head and neck move forward, upward, and open your mouth, showing a posture of trying to inhale, with a wheezing sound. Severe cases, high dyspnea, spasmodic cough, can produce bloody mucus. If the secretion can not come out and block the trachea, it can suffocate to death. Sick chicken appetite decreased or disappeared, rapid weight loss, chicken crown purple, sometimes also discharge green thin feces, and finally died of exhaustion. The egg production of laying hens decreased or stopped rapidly and could not be recovered until 1-2 months after recovery. The course of the disease is 5ml for 10 days or more, and the undead recover after 8 MUE for 10 days, and some of them can become infected chickens.

4. the main pathological changes were in the trachea and larynx. At the beginning of the disease, the mucous membrane was congested and swollen with mucus. Then the mucus was degenerated, bleeding and necrotic, and the lumen became narrow. Three days after the course of the disease, there was a yellow-white fibrous caseous pseudomembrane. Due to severe coughing and spasmodic breathing, the exudate is mixed with blood clots and exfoliated epithelial tissue. In severe cases, inflammation can also spread to the bronchi, lungs and air bags, and even ascending to the infraorbital sinus.

5. The diagnosis of this disease often occurs suddenly and spreads quickly, and adult chickens occur most frequently. The morbidity is high, and the mortality varies greatly due to different conditions. The clinical symptoms are typical, such as open mouth breathing, wheezing with rales, and bloody mucus when coughing. The trachea showed catarrhal and hemorrhagic inflammation. When the symptoms are not typical, laboratory examination can be carried out.

6. There is no effective drug for prevention and treatment at present. When the disease occurs, it can be treated symptomatically, and antibiotics are used to prevent secondary infection. Breeding and management equipment and chicken sheds should be disinfected. Sick chickens should not be raised in mixed herds with susceptible chickens. In the epidemic area of infectious laryngotracheitis, chickens can be immunized with attenuated vaccine by eye-dipping and nasal dripping. The time of the first immunization was about 4 weeks old, and the second immunization was carried out after 6 weeks.