Anaplasmosis, 2003

Human anaplasmosis (HA) is the new nomenclature for the disease formerly known as human granulocytic ehrlichiosis. HA (caused by the rickettsia Anaplasma phagocytophilum) is transmitted to humans by Ixodes scapularis (deer tick or black-legged tick), the same tick that transmits Lyme disease.

Similar to Lyme disease, HA case numbers also dropped during 2003, from a record high of 149 cases in 2002 (3.0 per 100,000 population) to 78 cases (1.6 per 100,000). Fifty-five (71%) case-patients reported in 2003 were male. The median age of case patients was 61 years (range, 3 to 91 years). The peak in onsets of illness occurred in June and July (43 cases [55%]). Co-infections with Lyme disease and HA can occur from the same tick bite; during 2003, five HA case-patients (6%) also had objective evidence of Lyme disease. The risk for HA is highest in the same east-central Minnesota counties where the risk of Lyme disease is greatest, including Aitkin, Crow Wing, Cass, Pine, and Morrison Counties.

For additional information on HA, see “Lyme Disease and Anaplasmosis in Minnesota, 2003” in the March/April 2004 issue (vol. 32, no. 2) of the Disease Control Newsletter.

• For up to date information see>> Anaplasmosis
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2003