Which blood donors are at risk for babesiosis?
Humans usually acquire babesiosis through the bite of a tick that has fed on an infected mouse. Rodents are reservoirs for B. microti. Babesia are parasites of many mammals and are major pathogens of cattle. Deer are important hosts for the ticks. They nourish and transport the ticks, spreading them from place to place, but do not appear to be infected. Most cases of babesiosis in the U.S. occur in the Northeast, particularly eastern Long Island, Shelter Island and Fire Island in New York; Cape Cod, Nantucket and Martha’s Vineyard in Massachusetts; and in mainland Connecticut. Cases have also been reported from the Midwest and Northwest. Some cases from the Northwest may be due to a different species of babesia. Serologic surveys in endemic areas have shown fairly high prevalence rates, ranging from 3.7% to 6.9%, and suggest that many infections are sub-clinical and/or patients do not seek treatment.
