Veterinary Preventive Medicine-II

DIAGNOSIS

• Specimens - Affected tissues (formalin-fixed) and serum.
• Presumptive diagnosis of BL is often based on the finding of tumors in the locations mentioned above upon clinical and gross necropsy examination.
• Microscopic examination of affected tissues is required to confirm the disease.
• It must be kept in mind that there are sporadic forms of non-viral bovine leukosis (thymic, multicentric); they usually affect younger animals.
• Identification of the agent : Virus can be isolated following in-vitro culture of peripheral blood lymphocytes from infected animals by electron microscopy or by BLV antigen detection in the culture supernatant.
• Proviral DNA can be detected in peripheral blood lymphocytes or tumors by the polymerase chain reaction.
• Serological tests : The antibody detection methods widely used are the agar gel immunodiffusion (AGID) assay using serum and the enzyme - linked immunosorbent assay (ELISA) using serum or milk.
• These tests have formed the basis for successful eradication policies in many countries. Other tests, such as radio-immunoassay, can also be used.
• A number of AGID and ELISA kits are available commercially.
• The virus can be isolated and cultivated in blood lymphocytes but this is not practicable for diagnosis.