Serologic comparisons of 4 Anaplasma isolates as measured by the complement-fixation test

Anaplasma marginale isolated from Virginia (VAM), from North Texas (NTAM), from Florida (FAM), and Anaplasma ovis from Idaho were used in these trials. Complement-fixation antigens from each of the 4 isolates were used to compare complement-fixing antibody titers of 10 cattle infected with VAM, 17 with FAM, and 6 with NTAM. Strong cross-reactions occurred with all antigens and sera. The homologous system generally showed higher average antibody titers. The serum antibody titers occuring with the A. ovis antigen were significantly lower than those seen with A. marginale antigens. Serum antibody titer differences as measured by FAM and NTAM antigens on sera from VAM, NTAM and FAM failed to reach significance. Serum antibody titer comparisons using VAM antigen were significantly different from those occurring with FAM and NTAM in most instances.