Immune responses of the camel (Camelus dromedarius) to contagious ecthyma (Orf) virus infection

An enzyme-linked immunosorbent assay (ELISA) was developed together with a western blotting technique for the detection of total and specific IgG and IgM antibodies to the contagious ecthyma (orf) virus in camel (Camelus dromedarius) sera and for identifying the seroreactive antigens of the virus. An outbreak of generalised contagious ecthyma in camels was diagnosed for the first time in Libya; the seropositivity rate in a herd with clinically affected camels was 37.9% (and was related to clinical signs) and in apparently normal herds was 0% to 6.8%. Two viral antigenic determinants (22 and 40 kDa) were shared by the western blotting patterns of all the positive camel sera tested, another viral antigenic component of 28 kDa was shared by the positive sera with high ELISA titres. Very close similarity was seen with the western blot of orf-positive sheep sera. It is considered that the ELISA technique was valid for orf serodiagnosis in the camel and could be usefully applied to other species at risk of orf infection.