Babesiosis, 2007

Babesiosis is a malaria-like illness caused by the protozoan Babesia microti. This parasite is transmitted to humans by bites from Ixodes scapularis (the blacklegged tick or deer tick), the same vector that transmits the agents of Lyme disease and Anaplasmosis (HA). B. microti can also be transmitted by blood transfusion.

In 2007, a record number of 24 babesiosis cases (0.5 per 100,000 population) were reported. This is a 22% increase from the previous record of 18 cases (0.4 per 100,000) in 2006. The frequency of babesiosis cases since 2006 is notably higher than the median number of cases reported annually from 1996 to 2005 (median, 2 cases; range, 0 to 10). Nineteen (79%) babesiosis case-patients reported in 2007 were male. The median age of case-patients was 63.5 years (range, 17 to 101 years). The peak in onsets of illness occurred in July and August (14 cases [61%]). In 2007, 74% of case-patients were hospitalized for their infection, for a median duration of 6 days (range, 2 to 15 days). One case-patient died from complications of babesiosis in 2007.

Babesiosis co-infections with Lyme disease or HA can occur from the same tick bite, although the majority of babesiosis infections are asymptomatic. During 2007, four (17%) babesiosis case-patients also had objective evidence of Lyme disease, and three (13%) had objective evidence of HA.

The risk for babesiosis is highest in many of the same Minnesota counties where the risk of Lyme disease and HA is greatest, especially in east-central and north-central Minnesota and western Wisconsin.

• For up to date information see>> Babesiosis (Babesia microti)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2007