Protozoan Diseases - BABESIOSIS

(Piroplasmosis)

AGENT:

Babesiosis in humans is a rare intraerythrocytic infection caused by Babesia divergens and B. microti.

RESERVOIR AND INCIDENCE

Natural hosts for B. microti are various wild and domestic animals, particularly the white-footed mouse and white-tailed deer. With extensions of the deer's habitat, the range of human infection appears to be increasing. In the USA, the parasite has been found in coastal and island areas of the northeast and mid-Atlantic states as well as Wisconsin, Minnesota, and California. B. divergens occurs in Europe.

TRANSMISSION:

Humans are infected as a result of Ixodes tick bites, but transmission from blood transfusion has also been reported. Splenectomized, elderly, or immunosuppressed persons are the most likely to have severe manifestations.

DISEASE IN ANIMALS:

Many animals show only mild fever and recover spontaneously. Deaths, which occur commonly in cattle, are due to either anemic anoxia or pulmonary thrombosis. Other lesions stem from the hemolysis and include enlarged spleen, liver, and hemoglobinuric nephrosis.

DISEASE IN HUMANS:

B. microti infection lasts a few weeks to a month; the illness is characterized by irregular fever, chills, headache, diaphoresis, myalgia, and fatigue but is without malaria-like periodicity of symptoms. Most patients have a moderate hemolytic anemia, and some have hepatosplenomegaly. The disease is self-limited and most patents recover without sequelae. Infection with B. divergens has only been reported in splenectomized patients and progresses rapidly with high fever, severe hemolytic anemia, jaundice, hemoglobinuria, and renal failure; death usually follows.

DIAGNOSIS:

ID of the intraerythrocytic parasite on Giemsa-stained blood smears or serology.

TREATMENT:

B. divergens: blood transfusions, renal dialysis, pentamidine plus trimethoprim-sulfa.
B. microti: Treat symptomatically since most case are self-limiting. In splenectomized patients, quinine plus clindamycin and transfusions.

PREVENTION/CONTROL:

Control rodents and ticks. Vaccinate livestock.