Babesiosis, 2008

Babesiosis is a malaria-like illness caused by the protozoan Babesia microti or other Babesia species. 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. Babesia parasites can also be transmitted by blood transfusion.

In 2008, a record number of 29 babesiosis cases (0.6 per 100,000 population) were reported. This is a 21% increase from the previous record of 24 cases (0.5 per 100,000) in 2007. 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). Fifteen (52%) babesiosis case-patients reported in 2008 were male. The median age of case-patients was 55 years (range, 11 to 92 years). Onsets of illness were elevated from June through September and peaked in July (25% of cases). In 2008, 68% of case-patients were hospitalized for their infection for a median duration of 9 days (range, 1 to 24 days). One case-patient died from complications of babesiosis in 2008. Three babesiosis case-patients during 2008 likely acquired their infections from blood transfusions.

Babesiosis co-infections with Lyme disease or anaplasmosis can occur from the same tick bite, although the majority of babesiosis infections are asymptomatic. During 2008, two (7%) babesiosis case-patients were also confirmed cases of Lyme disease, and four (14%) were confirmed or probable cases of anaplasmosis.

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, 2008