PubMed1985
The currently available methods for the serological and immunological diagnosis of human parapoxvirus infection (milker's nodule, farmyard pox) are demonstrated by the case of a man infected by contact with sheep carrying ecthyma contagiosum lesions. Compared to virus identification by electron microscopy, cell culture and animal experiments, identification of viral antigen in skin biopsies is equally sensitive during the first 2 weeks of the disease, whereas it is far more sensitive afterwards. The diagnosis of a parapoxvirus infection may be confirmed, even after skin lesions have healed, by assays for agglutinating, complement fixing, neutralizing and flocculating antibodies in patients' serum, the most sensitive method currently used being immunofluorescence and enzyme assays (ELISA). Additionally, antibodies on cell surfaces, which are regularly found in parapoxvirus infection, may be used to confirm the diagnosis by testing recall antigens. By means of serological assays used for routine purposes as well as by negative staining, the genus parapoxvirus can be identified, but not the species. Cross immunity between orthopoxvirus and parapoxvirus do not occur. The three species of the genus of parapoxvirus may be differentiated by DNA-hybridization techniques or by surface structure analysis using immunoelectron microscopy. According to clinical, histological, serological and electron microscopical features, the diseases caused by the three parapoxvirus species are identical in humans. The clinical entity in humans should be called farmyard pox regardless of the species of virus isolated.