Diagnosis of Babesia equi infection: an update on the methods available.

Abstract

Abstract Equine babesiosis, a tick-transmitted haemoprotozoan disease caused by Babesia equi , is globally distributed and poses a serious threat in international movement of horses. The earlier conventional sero-tests available were not sufficient for sensitive and specific diagnosis of the latently infected equids. Hence, in the last decade, new improved diagnostic methods were designed for accurate and rapid diagnosis. Demonstration of parasites in the blood collected from a carrier animal by blood smear examination or by in vitro cultivation technique is an absolute and reliable method of confirmation. These techniques are not very sensitive and, recently, geographically conserved genes in B. equi genome ( ema -1 and ema -2) were exploited using PCR (and nested PCR) and DNA probes. These techniques proved to be an efficient tool in specific diagnosis, but are limited to well-equipped laboratories. Many different serodiagnostic tests have been described, such as complement fixation test (CFT), indirect fluorescent antibody test (IFAT) and enzyme-linked immunosorbent assay (ELISA). A remarkable improvement in ELISA has been made and problems associated with native antigen were overcome by production of recombinant antigen. Competitive inhibition ELISA (CI-ELISA; a specific monoclonal-antibody-based assay) has proved to be highly sensitive and specific and has recently been prescribed by Office International des Epizooties (OIE) as a test for international trade. Latex agglutination test (LAT) and immunochromatographic test (ICT) are the new standardized tests based on specific recombinant antigen and much quicker than the other available diagnostic tests: further validation may, however, be required.