Observations on the use of Anaplasma centrale for immunization of cattle against anaplasmosis in Zimbabwe

Abstract

The efficacy of vaccine containing A. centrale against 3 Zimbabwean isolates of A. marginale was evaluated between November 1994 and June 1996. 93 cattle were used in 3 pen trials and 9553 cattle from 16 farms in a field trial. A. centrale stocks used for vaccination of cattle in pen trials were imported from South Africa and from Australia. The vaccine used in the field trial was of Australian origin. The results of pen trials indicated that 2 vaccine stocks were comparable and that neither provided adequate protection against challenge with 2 of 3 A. marginale isolates. The field observations indicated that the vaccine had high antigenicity and produced mild reactions in post-vaccination period. The users were generally satisfied with the cost and efficacy of the vaccine. However, 3 unconfirmed cases of death caused by anaplasmosis were reported on 1 farm 12 months after last vaccination. It is suggested that the use of A. centrale vaccine is justifiable until more effective alternative becomes available.