Epidemiology of bovine anaplasmosis in beef calves in northern Queensland.

Natural infection of calves with Anaplasma marginale was studied in two endemic areas of tropical north Queensland. Infection, assessed by a micro-complement fixation test, occurred throughout the year but was most frequent just after the summer wet season. Infection was clinically inapparent. Calves vaccinated with A. centrale did not show improved growth rate when compared with non-vaccinated calves. The complement fixation test was shown to be most effective in the detection of recent infections.