Clinical Pathology: General Principles, Hematology & Coagulation

• Babesia microti is a parasite transmitted to humans through bites of the Ixodes species of ticks. These ticks are the same vector for Lyme disease and ehrlichiosis. The intermediate hosts are deer and rodents.

• Babesia sporozoites are transferred while the tick is feeding. They invade erythrocytes and multiply. Babesia can also be transfusion-transmitted from a blood donor with a subclinical infection.

• Clinical symptoms can be mild and unnoticed, or they can be more severe, with fever, chills, and severe hemolytic anemia. Very young, elderly, and immunocompromised patients are more susceptible to severe infection.

• Peripheral blood smear shows intraerythrocytic rings forms. These forms can be mistaken for malaria. The appearance of Maltese crosses is essentially diagnostic for Babesia.

• Often, the clinical history is helpful in distinguishing malaria from Babesia. Malaria will be found in patients traveling to endemic malarial regions (e.g., sub-Saharan Africa, Asia), whereas patients with Babesia will more likely have a travel history to Long Island, New York, or Connecticut.

• The hemolytic anemia can be treated with antibiotics. If the parasitemia is very high and the patient has severe disease, red cell exchange can be performed.