First record of locally acquired human babesiosis in Canada caused by Babesia duncani: a case report

OBJECTIVES: The aim of this clinical assessment was to ascertain whether a 70-year-old Canadian patient, who had no history of out-of-country travel, had contracted a Babesia infection. METHODS: The adult human male developed constitutional symptoms, which included sweats, chills, and immobilizing fatigue, and was screened for human babesiosis. Subsequent testing included a complete Babesia panel that consisted of B. microti immunoflourescent antibody IgM and IgG, B. duncani immunofluorescent antibody IgM and IgG, Babesia PCR, and Babesia fluorescent in situ hybridization (FISH) test. RESULTS: Both the IgM serology and the molecular FISH RNA probe were positive for B. duncani; all tests for B. microti were negative. Based on clinical symptoms and laboratory tests, the patient was diagnosed with human babesiosis. Interestingly, the patient’s wife also was confirmed positive using serological and molecular testing. CONCLUSIONS: This is the first report of a locally acquired case of human babesiosis in Canada caused by Babesia duncani. The geographical distribution of B. duncani in North America is much greater than previously anticipated, especially north of the Canada-United States border. Since the patient was bitten by a blacklegged tick, Ixodes scapularis, a carrier of multiple zoonotic pathogens, the author suggests that this tick species is a vector of B. duncani. Health-care providers must be aware that B. duncani is present in Canada, and poses a public health risk.