Feline immunodeficiency virus status of Australian cats with lymphosarcoma

Objective To determine the FIV status of Australian cats with lymphosarcoma and relate this to patient characteristics, tumour characteristics (tissue involvement, histological grade and immunophenotype), haematological and s erum biochemical values and FeLV status of affected cats. Design Prospective study of 101 client-owned cats with naturally-occurring lymphosarcoma. Procedure Western blot analysis, ELISA and immunochromatography were used t o detect FIV antibodies in serum from cats with lymphosarcoma. Results On the basis of Western blot analysis (which was considered the mos t accurate method for determining FIV status), 50/101 (50%) of cats with na turally-occurring lymphosarcoma were positive for FIV antibodies. Of these 50 cats, 35 had tumours of B-cell phenotype, 13 had T-cell tumours and 2 ha d tumours classified as non-B/non-T. Tumours from eight of these FIV-positi ve cats contained FeLV gene sequences, including a 9-month-old cat with FeL V antigenaemia. Compared with FIV-negative cats with lymphosarcoma, FIV-pos itive cats were more likely to be domestic crossbreds (P = 0.004), male (P = 0.048) and have atypical (especially nasal) forms of lymphosarcoma (P = 0 .09). Only 39 of 107 (36%) blood or sera tested using ELISA were positive f or FIV antibodies (including 5 false-positives). Conclusions The prevalence of FIV infection was considerably higher in our cohort of cats compared with series of lymphosarcoma cases from the Norther n hemisphere. A positive FIV status was strongly associated with lymphosarc oma in Australian cats and it is possible that this infection may predispos e to the development of lymphoid neoplasia. The presence of FIV infection w ould have been underestimated if commercial kits alone had been used for se rology.