babesiosis

Babesiosis is a malaria-like infectious disease caused by protozoan parasites of the genus Babesia, which invade red blood cells. In humans, the most important species are Babesia microti in the United States and parts of Europe, with other species such as B. divergens, B. duncani, and B. venatorum reported in various regions. The clinical presentation ranges from asymptomatic infection to fever, hemolytic anemia, and organ dysfunction.

Transmission occurs mainly through bites of Ixodes ticks, the same ticks that transmit Lyme disease and anaplasmosis. Ticks acquire Babesia by feeding on infected wildlife reservoirs (commonly small mammals such as Peromyscus or voles; deer serve as hosts for ticks). Humans acquire infection when an infected tick feeds on them. Co-infection with other tickborne pathogens is possible. Babesia infections are most common in the northeastern and upper midwestern United States, as well as parts of Europe and Asia.

Symptoms typically appear one to four weeks after a tick bite and may include fever, sweats, fatigue, myalgia, headache, and hemolytic anemia. Severe disease can occur in asplenic individuals, the elderly, or immunocompromised patients, potentially leading to jaundice, renal impairment, or respiratory failure.

Diagnosis is by identification of intraerythrocytic parasites on blood smear (often showing small ring-form parasites or the characteristic Maltese cross) or by molecular methods (PCR). Serology and parasite burden measurements may aid in diagnosis and monitoring.

Treatment for mild to moderate disease is usually atovaquone with azithromycin for about 7–10 days; severe disease is treated with clindamycin and quinine, with exchange transfusion considered for high parasitemia. There is no vaccine. Prevention focuses on tick avoidance, prompt bug checks, and protective measures in endemic areas, given the possibility of co-infection with other tickborne pathogens.