Occurrence of viral thymic lymphoma associated with generalized lymphadenopalty and splenomegally in a 3.5 month old Holstein female calf

In a dairy farm with 1600 milking cows، a 3. 5- month old Holstein female calf showed a prominent hard subcutaneous mass at the lower part of the neck resulted in rumen bloat and dyspnea. In postmortem examination of the calf، apart from huge mass of thymus، astonishing enlargement of innumerable lymph nodes and a large spleen were noticed as well. In histopathologic study، replacement of the thymus، lymph nodes and spleen tissues with immature malignant lymphocytes were found. The adjacent muscles and fats of the extra-thoracic thymus lymphoma were invaded by the neoplastic lymphoid cells. CBC of the patient showed leukocytosis (more than 45000) and lymphocytosis (higher than 93% with 2% atypical lymphocyte). PCR of blood sample of the calf was positive and in ELISA test، the serum antibody was negative (28pp). PCR and ELISA of the mother of this calf were negative while PCR of a sample from the dairy milk tank was strongly positive. It is suggested that due to lack of maternal passive immunity and immaturity of immune system، following ingestion of BLV- contaminated milk، the calf became infected، resulted in occurrence of atypical and widespread viral lymphoma.. By the best knowledge of the authors this is the first report of this kind of calf lymphomsarcoma world-wide.