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Anaplasmosis

Viral and Parasitic Diseases, USDA, APHIS, Federal Building, Hyattsville, MD 20782

ABSTRACT

Excerpt: The organism is Anaplasma marginale which is probably a rickettsia though some still consider it a protozoa. Anaplasma marginale behaves like a protozoa, so for many years it was considered as such. However, it is much smaller than protozoa and, as the name implies, is without cytoplasm. Morphologically, it more closely resembles rickettsia.

The disease is not contagious because the organism is not mobile or invasive and must be placed in the blood stream of susceptible animals. This is unusual as most diseases we deal with are contagious and are passed directly from animal to animal. This is accomplished usually by shedding of the causative virus or bacteria in the feces, urine, or nasal or other secretions.

East of the Rocky Mountains transmission is mainly by horseflies though large populations of mosquitos can transmit the disease. Also, deer flies and other biting and blood sucking insects may transmit the disease. The American Dog Tick (Dermacentor variabilis) can transmit the disease but is not an important vector.