Avian leukemia is a general term for various tumor diseases in poultry caused by avian leukemia virus and avian sarcoidosis virus. It is a type of tumor mainly caused by hematopoietic cell proliferation caused by AL virus (ALV). Diseases, including lymphocytic leukemia, erythroblastic leukemia, myeloblastic leukemia, and myelocytoma leukemia. Since ALV was first reported and isolated in 1908, the disease has occurred and become prevalent in many countries around the world. Broiler chickens, laying hens and local breed chickens in my country are also commonly infected by avian leukemia virus, and its morbidity and mortality are even as high as 30 to 40, which seriously affects the sustainable development of my country's poultry industry and is one of the important epidemic diseases currently endangering the development of my country's poultry industry. The main hazards include death of sick chickens due to tumors, delayed sexual maturity of infected chickens, decreased egg production rate of hens, decreased egg weight, decreased fertilization rate and hatching rate, and immune suppression, which can easily lead to multiple infections of other pathogens in infected chickens. infection, poor immune response to vaccines. So far, there is no effective treatment for avian leukemia, let alone an effective vaccine. In view of this situation, how to effectively prevent and control the occurrence of avian leukemia in breeder farms during production is an issue that animal husbandry and veterinary workers across the country have been concerned about and struggled to explore. Therefore, some experts suggest that preventive measures mainly rely on the purification of the population.

There are two modes of transmission of the disease: vertical transmission from hens to offspring through eggs, and horizontal transmission through direct or indirect contact between chickens. Sick chickens and latently infected chickens are the main sources of infection. Among them, adult hens with viremia infect many tissues and organs of chicken embryos through vertical transmission, and pass the virus to their offspring. Most of the tissues and organs of these chicken embryos are infected with the virus. Virus particles, which are highly contagious, cause horizontal infection through the feces of chicks; while viremic, antibody-free (VA-) chickens have high levels of virus in the blood and tissue fluid, although this type of infected chickens It accounts for a small proportion of all chicken serotypes, but it spreads avian leukemia virus to its offspring at a high rate and is an important source of infection. Among infected chicken flocks, most chicken types are aviremic, There are antibody (V-A) serotypes, which have extremely high transmission rates through horizontal transmission through direct or indirect contact. Under natural circumstances, hens are more susceptible than roosters. Chickens aged 4 to 10 months are usually more susceptible to the disease. That is, chickens that are sexually mature or about to become sexually mature will have a progressive disease. The susceptibility of chickens of different breeds varies greatly.