The Emergence of Clinically Relevant Babesiosis in Southwestern Wisconsin.

OBJECTIVE To determine the frequency and characteristics of babesiosis cases, and to assess the impact of the introduction of a tick-borne infection diagnostic panel on babesiosis diagnosis in the region surrounding La Crosse, Wisconsin, where babesiosis in non-travelers was previously rare. METHODS In the spring of 2013, we conducted a point-in-time survey of Ixodes scopuloris ticks for the presence of Babesia microti. We also conducted a retrospective study of all babesiosis cases diagnosed in our health system between January 1, 2004, and November 1, 2013. Finally, we compared the number of babesiosis cases diagnosed during the study period before and after the June 1, 2012, introduction of a tick-borne infection diagnostic panel in our organization. RESULTS Babesia microti was present in 5% of ticks surveyed in our region. Twenty-two cases. of babesiosis were diagnosed in our organization during the study period-19 since 2010. The tick-borne infection diagnostic panel was used widely by clinicians, with an attendant increase in babesiosis diagnoses. CONCLUSION Babesiosis should be considered endemic in southwestern Wisconsin, and testing should be considered for patients with compatible clinical and laboratory features.