anaplasmose

Anaplasmose, or anaplasmosis, is a tick-borne infection caused by bacteria of the genus Anaplasma. The human pathogen is Anaplasma phagocytophilum, an intracellular bacterium that infects neutrophils. Other Anaplasma species affect animals, most notably Anaplasma marginale in cattle and Anaplasma ovis in small ruminants. Transmission occurs through bites of ixodid ticks, especially Ixodes species (for example Ixodes scapularis in North America and Ixodes ricinus in Europe). Reservoirs include wild mammals and domestic animals.

In humans, onset typically occurs 5 to 14 days after a tick bite. Illness is usually febrile with fever, headache, myalgia and malaise; nausea and cough may occur. Laboratory findings often include leukopenia and thrombocytopenia with mild liver enzyme elevations. Severe disease can occur in older adults or those with underlying conditions.

Diagnosis relies on serology or molecular detection of Anaplasma DNA in blood by PCR during acute illness. Morulae may be seen in neutrophils on blood smear in some cases. Treatment is most often doxycycline, started empirically when the diagnosis is suspected.

Prevention emphasizes avoiding tick exposure and prompt tick removal, use of repellents and protective clothing, and landscape management to reduce tick habitats. Most people recover with appropriate antibiotic therapy. In animals, infection can cause bovine anemia and economic losses, highlighting the veterinary importance of tick control.