Development of an ELISA system for detection of anti-Anaplasma marginale antibodies in cattle in Brazil

An ELISA test was developed for detecting antibodies against Anaplasma marg inale in bovine sera. Four antigenic preparations were produced from infect ed red blood cells. Some aliquots of this preparation were stored at -70 de grees C with 30% DMSO in phosphate-buffered saline (PBS) and others were ly sed with 0.9 % NH4Cl and stored at - 20 degrees C. Typical anaplasmal struc tures were seen by electron microscopy in the antigenic preparations contai ning the erythrocytes that had been stored with DMSO. The performance of th e ELISA test was evaluated by testing 298 positive serum samples collected from immunized cattle, 39 negative serum samples collected from cattle impo rted from areas free of A. marginale and 50 samples collected from cattle n aturally infected in the field. The test gave a specificity of 94.87 % and a sensitivity of 100 %.