CONFIRMATION OF OCCURRENCE IN HUNGARY OF CONGENITAL CEREBELLAR HYPOPLASIA IN CALVES DUE TO BVDV

The authors report the first well-documented occurrence in Hungary of congenital cerebellar hypoplasia in calves due to BVDV, a disease char acterised by fetopathogenicity and nervous symptoms. In a large scale cattle herd in Hungary there was a cluster of 10-12 abortions, stillbi rths and births of calves showing ocular lesions and nervous symptoms that almost invariably died within a few (2-9) days. There were 2 dead fetuses and 2 sick animals sent to laboratory examination. Necropsy a nd histopathology of the visceral organs revealed no pathognomonic sig ns, but thickening and hyperaemia of the meninges and partial absence of the cerebellum were noted. Virus isolation in cell culture identifi ed a virus strain with a cytopathic effect typical of BVDV. The presen ce of a cytopathic BVDV strain was confirmed by antigen capture ELISA which also detected a non-cytopathic strain. The authors hypothesise t hat the complex pathogenesis of the disease caused by BVDV cannot simp ly be explained on the basis of the equation: virus + host = disease; as cows that have recovered from natural virus infection, have normal host defense mechanisms, and are not persistently viraemic, can have i .) seropositive and persistently viraemic, yet healthy calves, as well as ii.) sick ones with cerebellar hypoplasia which are also seroposit ive and persistently viraemic; whereas cows that have recovered from n atural virus infection, have normal host defense mechanisms, and are p ersistently viraemic can have iii.) seropositive, and persistently vir aemic sick calves with cerebellar hypoplasia, as well as iv.) healthy seronegative, nevertheless persistently viraemic (immuntolerant) calve s. The authors recommend that in addition to the organs of sick animal s, heparinised blood samples should also be sent for routine laborator y diagnosis of diseases caused by BVDV so that antigen capture ELISA t est can be performed either on its own, or complemented by other tradi tional virological methods, such as virus isolation in cell culture.