Masking of two in vitro immunological assays for Mycobacterium bovis (BCG)in calves acutely infected with non-cytopathic bovine viral diarrhoea virus

Acute infection of calves, previously vaccinated with bacille Calmette-Guer in (BCG), with non-cytopathic viral diarrhoea virus (BVDV) resulted in the temporary suppression of two in vitro assays used to monitor Mycobacterium bovis infection. Lymphocyte proliferation and interferon-gamma production b y whole blood cultures containing purified protein derivatives prepared fro m Mycobacterium avium (PPD-A) and M bovis (PPD-B) were markedly suppressed. The implication is that acute infections of cattle with non-cytopathic BVD V may temporarily compromise diagnostic tests for M bovis infections and re sult in a failure to identify cattle with tuberculosis.