Babesiosis is caused by hemoprotozoan parasites of the genus Babesia.  While more than 100 species have been reported, only a few have been identified as causing human infections.  Babesia microti and Babesia divergens have been identified in most human cases, but variants (considered different species) have been recently identified.  Little is known about the occurrence of Babesia species in malaria-endemic areas where Babesia can easily be misdiagnosed as Plasmodium.

Symptoms

Most infections are probably asymptomatic, as indicated by serologic surveys.  Manifestations of disease include fever, chills, sweating, myalgias, fatigue, hepatosplenomegaly, and hemolytic anemia.  Symptoms typically occur after an incubation period of 1 to 4 weeks, and can last several weeks.  The disease is more severe in patients who are immunosuppressed, splenectomized, and/or elderly.  Infections caused by B. divergens tend to be more severe (frequently fatal if not appropriately treated) than those due to B. microti, where clinical recovery usually occurs.

Treatment

Treatment with clindamycin plus quinine or atovaquone plus azithromycin.

References:

Herwaldt BL, Persing DH, Précigout EA, et al. A fatal case of babesiosis in Missouri: Identification of another piroplasm that infect humans. Ann Intern Med 1996;124:643-65.

Pershing DH, Herwaldt BL, Glaser C, et al. Infection with a Babesia-like organism in northern California. N Engl J Med 1995;332:298-303.