Babesia odocoilei was found to infect two previously unknown host species, desert bighorn sheep (Ovis canadensis nelsoni) and musk oxen (Ovibos moschatus), both of which are members of the family Bovidae. Previously, B. odocoilei has been reported in only Cervidae hosts. New geographic regions where B. odocoilei infections have not been reported previously include Pennsylvania and New York, where fatal babesiosis has occurred in reindeer (Rangifer tarandus tarandus); New Hampshire, where elk (Cervus elaphus canadensis) have been affected; and California, home of the infected desert bighorn sheep. Infection with B. odocoilei in these hosts was confirmed by parasite small subunit ribosomal RNA gene sequence analysis. A serosurvey for B. odocoilei antibody activity in New Hampshire showed prevalence rates of 100% at two elk farms and 12% at another farm. Control of potential vector ticks, Ixodes scapularis, especially when translocating livestock, is imperative to prevent outbreaks of babesiosis in managed herds of potential host species.

Piroplasms isolated from a farmed reindeer and elk in Wisconsin were determined to be Babesia odocoilei, based on morphology and ribosomal RNA (rRNA) analysis. Different clinical manifestations were observed in the two host species. The reindeer was parasitemic and exhibited acute babesiosis resulting in death, while the elk showed no parasites in blood smears and no overt clinical signs of babesiosis. B. odocoilei was, however, readily cultured from elk erythrocytes. Small subunit rRNA gene sequences from the two isolates were identical to that previously reported for B. odocoilei. Internal transcribed spacers 1 and 2 and 5.8S rRNA sequence analysis showed an overall identity range of 94.3-98.1% to corresponding sequences from three previously reported B. odocoilei isolates, but the Wisconsin reindeer B. odocoilei shared only 87.3% identity with a previously reported Babesia sp. isolated from a reindeer in California (RD61).