Anaplasmosis

• Cause: Anaplasma phagocytophilum (granulocytic anaplasmosis), Anaplasma platys (thrombocytotropic anaplasmosis).First Described: First reports of A. phagocytophilum came from sheep in 1951 (Scotland). Canine infection was first reported in the United States (California) in 1982 and in domestic cats in 1999. Anaplasma platys was first reported in the United States in dogs (Florida) in 1978 and in cats in Brazil in 2010. • Affected Hosts: Anaplasma phagocytophilum causes disease in dogs, cats, humans, ruminants (European strains), horses, and camelids. Anaplasma platys causes thrombocytopenia in dogs and cats. • Geographic Distribution: In the United States, A. phagocytophilum is most prevalent in the upper midwestern, northeastern, and western states. Infection also occurs throughout continental Europe and the United Kingdom, Asia, and Russia. The organism has been detected in dogs from Africa and South America. Anaplasma platys occurs throughout the Americas, Europe, Asia, Australia, the Middle East, and Africa. • Mode of Transmission: Tick vectors, primarily Ixodes ricinus-persulcatus complex ticks transmit A. phagocytophilum. Rhipicephalus sanguineus is suspected to be the major vector of A. platys, though this remains unconfirmed. • Major Clinical Signs: The major clinical signs of A. phagocytophilum infection are fever, lethargy, inappetence, and lameness due to polyarthritis. Vomiting, diarrhea, cough, and neck pain may occur. Infection by A. platys is usually associated with no signs, but fever and lethargy are possible. • Differential Diagnoses: Major differential diagnoses include other tick-borne diseases (such as ehrlichioses, rickettsioses, Lyme borreliosis, and babesiosis), bartonellosis, leptospirosis, primary immune-mediated disease, and lymphoma. • Human Health Significance: Anaplasma phagocytophilum causes human granulocytic anaplasmosis. Dogs act as sentinels for human infection and may carry unfed ticks to humans on their coats.