Anaplasmosis, 2014

Anaplasmosis, caused by Anaplasma phagocytophilum, is a rickettsial disease transmitted to humans by bites from Ixodes scapularis (the blacklegged tick or deer tick). Although anaplasmosis was initially referred to as human granulocytic ehrlichiosis, anaplasmosis and ehrlichiosis (due to Ehrlichia chaffeensis) are distinct diseases caused by different rickettsial species, and only anaplasmosis is endemic in Minnesota. In Minnesota, the same tick vector also transmits the etiologic agents of Lyme disease, babesiosis, ehrlichiosis (due to Ehrlichia muris-like), and a strain of Powassan virus. A. phagocytophilum can also be transmitted by blood transfusion.

In 2014, 448 confirmed or probable cases of anaplasmosis (8.3 cases per 100,000 population) were reported (Figure 1), down from the 627 cases reported in 2013. Despite occasional decreases in reported cases, the overall trend is an increase in yearly case totals. Two hundred ninety-two (65%) cases reported in 2014 were male. The median age of cases was 59 years (range, 3 to 87 years), 20 years older than the median age of Lyme disease cases. As is typical, most cases had illness onsets during the summer months, with 58% reporting illness onsets in June and July. In 2014, 124 (28%) cases were hospitalized at some point for their infection, with a median duration of 4 days (range, 2 to 17 days).

• For up to date information see>> Anaplasmosis
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2014