A flu-like syndrome in most patients; Patients with impaired immunity may develop severe babesiosis complicated by respiratory failure, DIC, CHF, & renal failure; [Harrison, p. 767-71] 1/2 of children & 1/4 of adults have subclinical infections. [Cecil]
In untreated patients, the febrile illness lasts several days to a few months. Some patients have hemolytic anemia and thrombocytopenia. [CCDM, p. 61] Arthralgias, headache, nausea, hepatosplenomegaly, leukopenia, and thrombocytopenia are common findings. Less than 20% of patients have cough and dyspnea. Relative bradycardia has been reported. Severe cases are associated with prior splenectomy. Complications include acute renal failure, pulmonary edema, disseminated intravascular coagulation, shock, and respiratory failure. [ID, p. 2304] Babesiosis mimics malaria. The illness begins 1-4 weeks after a tick bite or 4-9 weeks after transfusion. Additional findings are diarrhea, sweating, and elevated liver transaminases. Antibodies become detectable about 1 week after onset of symptoms. [Guerrant, p. 676-81] The ticks are only 2 mm in diameter and not usually seen. [PPID, p. 3168] Renal failure from intravascular hemolysis may progress to hypotension, coma, and death. [Guerrant, p. 678] Severe cases resembling falciparum malaria (high fever, hemolytic anemia, jaundice, and renal failure) are seen in elderly patients and patients with splenectomy and AIDS. [Merck Manual, p. 1375]
Babesiosis is endemic on several USA east coast islands and in southern Connecticut. The vectors are nymphal Ixodes ticks, and the agents are protozoan parasites of red blood cells. Asymptomatic infections are common. Transmission has been reported by blood transfusion and, rarely, congenital/perinatal. On blood smear examination, the parasite may be confused with plasmodium falciparum. Reservoirs are rodents in the USA and cattle in Europe. [CCDM, p. 62-3] In Europe, babesiosis is a rare disease usually caused by B. divergens. Nearly all patients are asplenic. In the US, babesiosis is caused by B. microti, and asymptomatic cases are common. Patients at risk for severe disease are asplenic, elderly, infected with HIV, or immunosuppressed. [PPID, p. 3165-71]
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Blood smear (Wright or Giemsa stain); Serology; [CCDM, p. 61] Tetrads pathognomonic but rarely identified; Blood PCR most sensitive test; Serology; [ABX Guide] Giemsa stained thin smears; PCR and serology; [Harrison, p. 771]