Prevention of lymphocytic leukemia in chickens

Chicken lymphocytic leukemia (LL) is a neoplastic disease caused by leukemia virus in near-sexually mature chickens or sexually mature chickens. It is characterized by slow epidemic, long course of disease, low mortality and tumors in liver, spleen, kidney and bursa of Fabricius. Chicken leukemia virus is a leukemia / sarcoma virus group of RNA tumor virus C of the family Retroviridae. This virus can not bear high temperature, 50 ℃, 8 minutes or 60 ℃. It can lose its activity in 30 seconds, but it can be preserved for several years at-60 ℃. (1) epidemic characteristics: only chickens are infected under natural conditions, and hens are more susceptible than cocks. The susceptibility of young chickens to white blood virus was high, but the disease was the highest in 4-10-month-old chickens. The transmission route of the disease is mainly through vertical transmission through eggs, and the eggs laid by 8-month-old infected hens contain the highest amount of virus. It can also be infected through direct or indirect contact, but because there must be close contact conditions and the virus is unstable, it is considered that contact transmission between chicken flocks is not important. (2) Clinical symptoms: diseased chickens showed pale crown and drooping flesh, shrinkage, occasional cyanosis, loss of appetite, emaciation, dilated abdomen, and the enlarged liver could be touched by hand. Egg production decreases, often accompanied by dysentery, and diseased chickens eventually die of extreme exhaustion. (3) autopsy changes: obvious lesions were common in liver, spleen, kidney and bursa of Fabricius and other organs of 4-month-old chickens, in which the incidence of liver and spleen was the highest, and tumors could also occur in other organs such as lung, heart and ovary. The surface of the tumor is smooth and glossy, grayish white or grayish black, soft texture, uneven section, few necrotic foci. According to the morphology and distribution, the tumors were divided into miliary type, nodular type, diffuse type and mixed type. The liver and spleen were the most obvious. (4) Green prevention and control measures: at present, there is no successful vaccine and effective treatment, so we should focus on the following comprehensive control measures: ① checks chickens (especially breeder chickens) every 1 to 3 months, and diseased chickens and suspected diseased chickens should be eliminated immediately in order to put an end to the infection of the disease. ② breeder eggs or breeder chickens should be purchased from chicken farms without lymphocytic leukemia, and breeder eggs should be strictly sterilized before hatching. ③ adult chickens and chicks were raised and managed in groups to prevent possible contact infection. ④ should strengthen feeding management and do a good job in disinfection, cleaning and hygiene of chicken sheds.