Anaplasma Phagocytophilum & Ehrlichia Chaffeensis

Anaplasma phagocytophilum and Ehrlichia chaffeensis are closely related tick-borne bacteria responsible for anaplasmosis and ehrlichiosis, respectively, both characterized as gram-negative and obligate intracellular pathogens. Notably, morulae-containing leukocytes seen on Wright-Giemsa stained peripheral blood smears are a distinctive diagnostic feature. Transmission to humans occurs through ticks, specifically via the black-legged tick (Ixodes spp.) for anaplasmosis and the lone star tick (Amblyomma americanum) for ehrlichiosis. The white-footed mouse serves as the reservoir host for Anaplasma phagocytophilum, while white-tailed deer host both Anaplasma phagocytophilum and Ehrlichia chaffeensis. Symptoms include flu-like illness, gastrointestinal disturbances, and marked laboratory abnormalities, including pancytopenia. Doxycycline is the preferred treatment for both infections.