Comparison of three methods of immunization against bovine anaplasmosis: an examination of postvaccinal effects

Normandy calves ranging in age from 7 to 11 months were immunized against bovine anaplasmosis, using a diluted virulent Anaplasma marginale stabilate of Colombian origin, diluted bovine blood containing an apparently mild strain of A marginale isolated in Colombia, or an attenuated A marginale vaccine of ovine origin from the United States. Calves given the stabilate generally showed a moderate degree of parasitemia and reduction in packed cell volume (PCV). Calves given the apparently mild Colombian isolate of A marginale developed a moderate parasitemia, a reduction in PCV, and in some instances, required treatment to moderate the premunization procedure. Calves given the attenuated vaccine showed minimal evidence of parasitemia and PCV reduction. Most of the immunized calves became seropositive in the complement-fixation test for anaplasmosis and all calves sampled showed evidence of a cell-mediated response, using the leukocyte migration-inhibition test.