Development and field evaluation of an ELISA to differentiate-infected from-vaccinated cattle.

Abstract

Immunization of calves withis used to prevent acute anaplasmosis caused by. Natural and vaccine-acquired immunity is detected through serologic tests based primarily onrecombinant major surface protein 5 (MSP5m) because it has 91% identity with MSP5 from(MSP5c). We developed a displacement, double-antigen, sandwich ELISA (ddasELISA) to detect antibodies againstorFor ddasELISA validation, we analyzed serum samples positive for antibodies againstspp. from cattle naturally infected with( = 300) or vaccinated with( = 255). Species-specific nested PCR (nPCR) assays were used to confirm infection. The optical density (OD) values obtained from antibodies directed at unique epitopes of(OD) or(OD) were used in the formula OD/OD. If the derived ratio was >0.38, the serum sample was considered positive for antibodies against, with 98.9% sensitivity and 98.0% specificity. In a field evaluation, we analyzed 702spp. antibody-positive serum samples from 34 herds by ddasELISA and nPCR; 571 were classified by ddasELISA as-infected or-vaccinated, with 84% agreement (κ = 0.70) between ddasELISA and nPCR. Our results indicate that ddasELISA could be used as a cost-effective alternative to molecular techniques to confirm infection within countries in which prevention is based on vaccination with.