Six weeks after being bitten by a deer tick, a pregnant 31-year-old woman began to have fever, chills, fatigue, and neck pain. During the fifth day of fever, she became jaundiced and was hospitalized. On physical examination, she was 37 weeks pregnant, febrile (temperature, 39.4°C [103°F]), and slightly jaundiced. There was no rash. Laboratory studies showed a hematocrit of 29 percent, a white-cell count of 5400 per cubic millimeter, a platelet count of 96,000 per cubic millimeter, and total bilirubin concentration of 5.4 mg per deciliter. Babesia microti were present in 2 percent of her erythrocytes (Figure 1FIGURE 1
Blood Smear Showing Intraerythrocytic Babesia microti (Arrows) (Wright's Stain, ×1000).
). B. microti DNA was detected in her blood by polymerase-chain-reaction (PCR) assay. She was treated with oral clindamycin (600 mg three times daily) and quinine (650 mg three times daily). The quinine caused nausea, which resolved with ranitidine. On the third day of hospitalization, she was afebrile and was discharged with instructions to complete seven days of therapy at home. Two weeks later, she gave birth to a normal 2.7-kg (6-lb) girl. The infant's blood was smear-negative, PCR-negative, and IgM antibody–negative for B. microti.1 Both the mother and the infant have remained well for two months.
The most common symptoms of babesiosis include fever, chills, fatigue, sweats, and headache. Babesial infection may be asymptomatic or mildly symptomatic or may cause severe illness. Malaria, another protozoal infection, is more severe during pregnancy than it is otherwise.2 Pregnancy may have predisposed our patient to increased severity of disease. There has been one previous case report of babesiosis during pregnancy.3 Vertically transmitted babesiosis has been reported once.4 In that case, the infant's illness resolved with clindamycin and quinine. The mother did not have symptoms and was not treated.
We chose to treat our patient with clindamycin and quinine because both cross the placenta and because quinine has been used to treat malaria in pregnancy. Although high-dose quinine can cause abortion in the first trimester, quinine at a standard dose has not been reported to have an oxytocic effect late in pregnancy.2 Another treatment option for babesiosis is azithromycin and atovaquone,5 but azithromycin does not cross the placenta and would be ineffective against established fetal infection. Our case documents the successful use of the combination of clindamycin and quinine for the treatment of babesiosis in a woman during the third trimester of pregnancy.