Babesia is a malaria-like parasite, also called a “piroplasm,” that infects red blood cells. Scientists believe Babesia microti is the most common piroplasm infecting humans, but they have identified over twenty piroplasms carried by ticks. In addition to transmission by a tick, babesia can be transmitted from mother to unborn child or through a contaminated blood transfusion. Currently, most blood banks do not screen donated blood for babesia.
Symptoms of babesiosis are similar to those of Lyme disease but babesiosis more often starts with a high fever and chills. As the infection progresses, patients may develop fatigue, headache, drenching sweats, muscle aches, chest pain, hip pain and shortness of breath. Complications include very low blood pressure, liver problems, severe hemolytic anemia, and kidney failure.
Babesiosis has been reported in North and South America, Europe, and southern and eastern Asia. In the United States, the primary agent of human babesiosis is Babesia microti. Cases of babesiosis caused by B. microti occur in southern New England and the northern Midwest. Additional cases of babesiosis caused by other species of Babesia occur primarily in the western U.S.; cases from Missouri and Kentucky have also been reported. In Australia, babesiosis of types B. duncani and B. microti has recently been found in symptomatic patients along the eastern coastline of the continent.
Diagnosis and Treatment
Commercial tests currently detect only two strains of Babesia and there are likely many strains yet to be discovered. The PCR (polymerase chain reaction) test can detect babesia DNA in the blood. The FISH (Fluorescent In-Situ Hybridization) assay can detect the ribosomal RNA of Babesia in thin blood smears. The lab can also test the patient’s blood for antibodies to Babesia. It may be necessary to run several different tests, and negative results should not be used to rule out treatment.