anaplasmosis ănˌəplăzmōˈsĭs [key], infectious blood disease in cattle, sheep, and goats, caused by a rickettsia of the genus Anaplasma. The organism parasitizes red blood cells, causing their destruction and producing emaciation, anemia, jaundice, and, occasionally, death. The disease is present in the warmer regions of the world and is most prevalent in the United States in the Gulf states, lower Plains, and California. Wild ruminants such as deer and antelope may be asymptomatic carriers. Transmission of the disease occurs mainly by the spread of infected blood through insect vectors, especially ticks and biting flies. It can also be transmitted in herds as they undergo any sort of large-scale procedure, such as dehorning.

The incubation period varies from three to four weeks. Infected animals first show a fever, which may rise to 107℉ (62℃) in severe cases, and then jaundice and anemia set in. Pregnant cows will frequently abort. Treatment of anaplasmosis consists of antibiotic therapy and blood transfusions, administration of fluids, and rest. Protecting well animals through the routine use of insecticides or insect repellents (to control insects that carry the rickettsia) or by vaccination limits the incidence of the disease.

Human granulocytic anaplasmosis, which was called human granulocytic ehrlichiosis when it was first identified (the causative agent, A. phagocytophilum, was classified at the time in Ehrlichia, another rickettsia genus), continues to be generically considered an ehrlichiosis.

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