Anaplasmosis, 2019

Anaplasmosis is a rickettsial disease caused by the disease agent Anaplasma phagocytophilum, which is transmitted by bites from Ixodes scapularis, the blacklegged tick. Although the organism that causes anaplasmosis was previously known by other names and thought to be a part of the genus Ehrlichia, anaplasmosis and ehrlichiosis (due to E. chaffeensis) are distinct diseases caused by different rickettsial species. The same tick vector also transmits the etiologic agents of Lyme disease, babesiosis, ehrlichiosis (due to E. muris), and Powassan virus. In rare circumstances, A. phagocytophilum may be transmitted by blood transfusion.

In 2019, 407 confirmed or probable cases of anaplasmosis (7.2 cases per 100,000) were reported, down from the 496 cases reported in 2018. Despite some annual fluctuations, including a decrease in cases the past 2 years, yearly case totals over time continue to trend upward, with a median of 620 cases reported per year since 2010 (Figure 1). In 2019, 245 (60%) confirmed or probable cases reported were male. The median age was 62 years (range, 0 to 92), 14 years older than the median age of confirmed Lyme disease cases, but close to the median age of confirmed or probable babesiosis cases (67). As is typical, most cases had illness onsets during the summer months, with 69% of cases reporting illness onsets in June, July, or August. In 2019, 133 (33%) cases were hospitalized for their anaplasmosis infection, with a median duration of 4 admission days (range, 2 to 374 days). Thirty-three (8%) cases reported complications (e.g., organ failure) due to anaplasmosis infection.

• Find up to date information at>> Anaplasmosis
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2019