Babesiose

Babesiose, also called babesiosis, is a zoonotic disease caused by intraerythrocytic protozoa of the genus Babesia. In humans, the most common species are Babesia microti in North America and Babesia divergens in Europe. The parasites infect red blood cells and are transmitted primarily by Ixodes ticks, which acquire the parasite from reservoir hosts such as small mammals and, in some regions, deer. Humans and animals can serve as incidental hosts when bitten by an infected tick.

Clinical features: Most infections in healthy individuals are mild or asymptomatic. When symptoms occur, they resemble malaria and may include fever, chills, sweats, fatigue, myalgia, and anemia. Severe or fatal disease can occur in older adults, asplenic individuals, or immunocompromised patients, and can involve hemolytic anemia, jaundice, acute kidney injury, and respiratory distress. Transmission can also occur via blood transfusion or, rarely, from mother to fetus.

Diagnosis: Suspected babesiosis is supported by visualization of intraerythrocytic ring forms or Maltese cross tetrads on a Giemsa-stained blood smear. Nucleic acid testing (PCR) and serology (antibody tests) aid confirmation, particularly in low-parasitemia cases or chronic infections.

Treatment: Uncomplicated cases may be treated with a combination such as atovaquone and azithromycin; severe disease or immunocompromised patients often require clindamycin plus quinine.

In very sick patients, exchange transfusion may be used.

Prevention and epidemiology: Prevention focuses on avoiding tick bites (protective clothing, tick repellents, prompt removal of ticks) and reducing tick exposure in endemic areas. Blood donor screening helps prevent transfusion-associated babesiosis in some regions. Babesia species circulate in many parts of the world, with human cases concentrated in North America and parts of Europe; animal babesiosis affects cattle and other livestock.