DETECTION OF ANAPLASMA-OVIS INFECTION IN GOATS BY MAJOR SURFACE PROTEIN 5 COMPETITIVE-INHIBITION ENZYME-LINKED-IMMUNOSORBENT-ASSAY

A competitive inhibition enzyme-linked immunosorbent assay (ELISA) bas ed on a major surface protein 5 (MSP5) B-cell epitope conserved among Anaplasma species was used to detect goats infected with Anaplasma ovi s. We examined strains of A. ovis isolated from goats in Kenya and dem onstrated that MSP5 and the target B-cell epitope, bound by monoclonal antibody ANAF16C1, were conserved. Sera from 149 goats in four region s of Kenya and from 302 goats in six U.S. states were tested far the p resence of epitope-specific antibodies with the MSP5 competitive inhib ition ELISA. Evidence that the assay can be used to detect A. ovis-inf ected goats includes the following: (i) 53 goats raised in confinement with arthropod central were all seronegative; (ii) six goats experime ntally infected with A. ovis seroconverted at the same time that they developed detectable rickettsemia; (iii) seroconverted goats remained seropositive, consistent with the persistence of A. ovis in goats and the presence of anti-MSP5 antibody in cattle persistently infected wit h Anaplasma marginale; and (iv) 119 of 127 known A. ovis-infected goat s in Kenya were seropositive. A. ovis infection, as determined serolog ically and by demonstration of infected erythrocytes, in goats from th e four regions in Kenya was highly prevalent. In contrast, despite the presence of A. ovis and competent arthropod vectors in the United Sta tes, the prevalence of infection appeared to be very low. The high pre valence in Kenya and the occurrence of anemia in persistently infected goats may be impediments to current efforts to increase milk yields o n small farms.