Babesia microti and Borrelia bissettii transmission by Ixodes spinipalpis ticks among prairie voles, Microtus ochrogaster, in Colorado

An endemic transmission cycle of Babesia microti was discovered in Colorado in the foothills of the Rocky Mountains. B. microti were found by PCR in 4 of 25 Ixodes spinipalpis tick pools tested (a 3.2 % minimum infection rate ) and in 87 % (13 of 15) of Microtus ochrogaster (the prairie vole) spleen and blood samples. Using naturally infected I. spinipalpis collected from w ild-caught M. ochrogaster as vectors, B. microti and Borrelia bissettii wer e successfully transmitted to laboratory-born M. ochrogaster. Neither I. sp inipalpis, nor M. ochrogaster (the prairie vole) have been previously repor ted as a vector or a reservoir host of B. microti. Unlike the east coast of the United States where Peromyscus leucopus is an important reservoir for B. microti, evidence for Peromyscus spp. (neither P. maniculatus nor P. dif ficilis) as B. microti reservoirs was not found in this study.