Isolation and identification of avian leukosis viruses: a review.

Avian leukosis virus (ALV) is the most common naturally occurring avian retrovirus that can cause a variety of neoplastic disease conditions in chickens. In addition to causing neoplasia, ALV is known to be associated with reduced productivity and other production problems in affected flocks. Biological and molecular assays for the detection of ALV are very useful in identification and classification of new isolates, safety testing of vaccines and in testing pathogen-free and other breeder flocks for freedom of virus infection. However, such assays are not particularly helpful in the diagnosis of virus-induced neoplastic disease of poultry, as avian oncogenic viruses are widespread and infection in the absence of tumor formation is common. Current technology based on molecular and antigenic characteristics of the virus is being used to develop more sensitive and specific procedures for isolation and identification of ALV. This review is primarily focused on the discussion of current technology most commonly used in isolation and identification of ALV associated with clinical disease in chickens.