Babesiosis is a malaria-like illness caused by a protozoan parasite and transmitted by a tick bite. Most human cases of babesiosis have occurred during the summer months in the northeastern United States, Maryland, Virginia, Georgia, Wisconsin, Minnesota, California, and Washington. Symptoms of babesiosis typically begin approximately 1 week after a tick bite and include malaise, anorexia, and fatigue followed several days later by fever, drenching sweats, myalgia, and headache. The clinical spectrum ranges from a mild self-limited illness to a serious disease with hemolytic anemia, renal failure, and hypotension primarily in patients of advanced age or in those with underlying chronic disease. Babesiosis can be diagnosed by examining Wright-stained or Giemsa-stained peripheral blood smears. The parasites invade erythrocytes and appear as small intraerythrocytic ring forms resembling the causative organism of malaria, Plasmodium falciparum. An indirect immunofluorescence test titer of greater than or equal to 1:64 is considered positive for babesiosis, although most patients with acute illness have titers of greater than or equal to 1:1024. The recommended treatment for this illness consists of a 7-day course of oral quinine plus clindamycin (by the intravenous or oral route). 
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