What causes babesiosis?

Updated: Apr 01, 2021
  • Author: Rachel E Strength, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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Answer

Babesia parasites from rodents (primarily the white-footed deer mouse but also the field mouse, vole, rat, and chipmunk) are transmitted to humans through tick bites in endemic areas. As such, babesiosis is more prevalent during the periods of high tick activity, such as spring and summer.  Restocking of deer populations and curtailment of hunting has increased deer herds in certain areas. The proximity of deer, mouse, and tick creates the conditions for human infection. 

Several reported cases of infection via blood transfusions from donors who lived in or traveled to an endemic area have been documented. [12, 13]  The incubation period in transfusion-associated disease appears to be 6-9 weeks. The rate of acquiring B. microti from a unit of packed RBCs has been estimated to be 1 in 600-1800 in endemic areas. 

Case reports of transplacental or perinatal transmission have also been documented. [3]


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