Anaplasmosis is caused by the organism Anaplasma marginale (Figure 1). It is transmitted by the cattle tick and is thought to be transferred mainly by direct movement of male ticks from carrier animals to other animals when they are in close contact. The course of the disease is more gradual than that associated with babesiosis, and the animals may be quite anaemic and jaundiced by the time clinical illness is noted.
The main clinical signs are pale and/or yellow mucous membranes (anaemia and/or jaundice); note that the urine does not turn red with anaplasmosis but may appear as a dark brown colour. Other clinical signs of anaplasmosis may include fever, loss of appetite, lethargy and depression, weakness and loss of condition.
As with babesiosis, many of these clinical signs are non-specific and can be associated with other conditions, so it is important to confirm the diagnosis by examination of blood smears under a microscope.