Serologic diagnosis of
anaplasmosis is currently done by the
complement-fixation, ELISA, and card agglutination tests. These tests have utilized A. marginale harvested from bovine erythrocytes as
antigen which is often contaminated with erythrocyte stroma. We are currently testing A. marginale propagated in a Ixodes scapularis cell line as
antigen for serologic tests. In this study, we report the use of the cell culture-derived A. marginale as
antigen for development of a rapid, semi-automated
latex agglutination test. Diluted serum and
latex (
polystyrene microspheres), sensitized with cell culture-derived A. marginale
proteins, were dispensed into 96-well microtiter plates. An initial reading of light transmission was recorded by a computer-interfaced scanning autoreader. After 30 minutes, the plates were mixed and read a second time, recording the delta % light transmittance. The sensitized
latex microspheres (
latex) agglutinated in the presence of A. marginale
antibodies, thus producing an increase in light transmittance. In preliminary tests, 724/977 of the sera were positive for A. marginale
antibodies with an apparent agreement of 83.3% when compared with the
complement-fixation test. Sensitization and sera dilution
buffers were shown to have a marked effect on the sensitivity and specificity of this assay. Results will be presented on the optimization of
buffers and the testing of sera from experimentally and field-infected cattle.