[Recent information about the orf virus of small ruminants]

New scientific findings in the field of immunobiology and diagnosis of parapoxvirus ovis (Orf-virus) as the causal agent of a zoonosis are presented. The adaptation of Orf-virus to cell lines and its in vitro multiplication without difficulties offer the possibility for extensive studies into the biology of parapoxviruses. The development of monoclonal antibodies (MAB) against an attenuated Orf-virus strain (D-1701) led to the elaboration of a simplified, cheap and highly sensitive "antigen detection ELISA" as a diagnostic tool. Moreover the MAB's can be used to identify parapoxvirus in cells of infected tissues (indirect immuno-peroxidase technique) which is an important precondition for more detailed surveillance of the pathogenesis of parapoxvirus infections. The immunobiological behavior of the Orf-virus in its natural hosts (small ruminants) as well as in non-susceptible species (e.g. laboratory animals) is explained by the course of cellular and humoral immune reactions following infection or vaccination. The problems of combat measures against contagious ecthyma (scabby mouth) of sheep and the human Orf-virus infections are discussed.