Experimental model of type II bovine viral diarrhea virus-induced thrombocytopenia in neonatal calves

Thrombocytopenia has been associated with type II bovine viral diarrhea vir us (BVDV) infection in immunocompetent rattle, but the mechanism is unknown . The purpose of the present study was to develop and characterize a model of type II BVDV-induced thrombocytopenia. Colostrum-deprived Holstein calve s were obtained immediately after birth, given a BVDV-negative and BVDV ant ibody-negative plasma transfusion, housed in an isolation facility, and ran domly assigned to either control (n = 4) or infected (n = 5) groups. Infect ed calves were inoculated by intranasal instillation on day 3 of age with 1 0(7) TCID50 of the prototype type II isolate, BVDV 890, whereas control cal ves were sham inoculated. Blood counts and virus isolations from serum, whi te blood cells, and platelets were performed daily until day 12 after infec tion, at which time all experimental calves were euthanatized, and patholog ic, virologic, and immunohistochemical examinations were performed. On phys ical examination, the control calves remained normal, but the infected calv es developed pyrexia and diarrhea characteristic of type II BVDV infection. The platelet count decreased in all infected calves, and a statistically s ignificant difference in the platelet count between control and infected ca lves was observed on days 7-12 after infection. In addition, the mean plate let volume and white blood cell counts also decreased. Examination of the b one marrow from the infected calves revealed immunohistochemical staining f or BVDV antigen in megakaryocytes and evidence of concurrent megakaryocyte necrosis and hyperplasia.