Anaplasmosis control and diagnosis in South Africa

Anaplasmosis is widespread in South Africa with more than 99% of the total cattle population at risk. Five tick species have been experimentally shown to be capable of transmitting Anaplasma in South Africa. Mechanical transmission through blood contaminated instruments and biting flies also occurs. Vaccination against Anaplasma marginale by administration of an Anaplasma centrale live-blood vaccine has been practiced in this country since 1912. Although generally a mild pathogen, Anaplasma centrale can cause severe clinical reactions following vaccination and also does not afford complete protection against all A. marginale isolates. Anaplasmosis vaccine is routinely available in a deep-frozen form and approximately 220,000 doses of vaccine are sold per annum. Microscopic examination of stained thin blood smears is still the most reliable and cost effective method of confirming a clinical diagnosis of anaplasmosis. Several diagnostic tests, such as the complement fixation tests, card agglutination test, and enzyme-linked immunosorbent assay (ELISA) have been developed to identify carrier cattle. A competitive inhibition ELISA test, based on antibody binding to a recombinant MSP-5 protein conserved among Anaplasma species, is routinely used at this laboratory.