A total of 93 Bos taurus cattle was used in pen trials to compare vaccine stocks of Anaplasma centrale
from South Africa and Australia (which stock came from South Africa in 1934) in protecting against
three virulent field isolates from clinical Anaplasma marginale infections. In addition, field observations
were made on the use of a vaccine, prepared from the Australian stock, in over 9553 cattle of
mixed age and breeds on 16 co-operator farms and at one communal dip.
The results of the pen trials indicated that the two vaccine stocks were comparable and that neither
provided adequate protection against two of the three isolates of A. marginale. The field observations
indicated that the vaccine was highly infective and produced mild reactions in most recipient cattle,
and that users were generally satisfied with the vaccine.
These somewhat conflicting results are discussed in the context of observations in Australia and future
vaccination against anaplasmosis in Zimbabwe.