Epidemiologic features of human babesiosis in Wisconsin, 1996-2005.

OBJECTIVE To characterize epidemiologic, clinical, and laboratory features of babesiosis occurring in Wisconsin residents. DESIGN Conduct a review of all cases of babesiosis reported to the Wisconsin Division of Public Health with onsets during 1996-2005. For case patients with onsets during 2004, pertinent medical records were reviewed and patient interviews were performed. INTERVENTIONS Increase awareness of the occurrence and recent trends and facilitate prompt, appropriate diagnosis and treatment of babesiosis. Increase awareness among clinicians of the Infectious Diseases Society of America guidelines for the management of babesiosis, Lyme disease, and human granulocytic anaplasmosis. MAIN OUTCOME MEASURES The study represents an analysis of data received through passive surveillance of a disease that is officially reportable to the Wisconsin Division of Public Health. Other than the description of the occurrence of babesiosis among Wisconsin residents, there were no planned outcome measures. RESULTS Of the 32 cases of babesiosis reported to the DPH during the study interval, 23 (72%) occurred during 2004 and 2005. The majority of cases occurred in northwestern and west-central Wisconsin. At least 6 patients were co-infected with other tick-borne pathogens. Anemia, thrombocytopenia, and elevation of liver transaminase levels were the most notable laboratory abnormalities among case patients. CONCLUSIONS The apparent increased incidence in babesiosis among Wisconsin residents should impact clinicians' workups for acute febrile illness with known tick exposure, especially in northwest and west central Wisconsin. Babesiosis should now also be considered in patients diagnosed with Lyme disease who have marked constitutional symptoms, especially those with anemia or thrombocytopenia.