White-tailed deer (Odocoileus virginianus) develop spirochetemia following experimental infection with Borrelia lonestari.

Borrelia lonestari is considered a putative agent of southern tick-associated rash illness (STARI) and is known to occur naturally only in lone star ticks (Amblyomma americanum) and white-tailed deer (Odocoileus virginianus). We used a low passage isolate of B. lonestari (LS-1) to inoculate white-tailed deer, C3H mice, Holstein cattle, and beagles. Animals were monitored via examination of Giemsa and acridine orange stained blood smears, polymerase chain reaction (PCR), indirect fluorescent antibody (IFA) test, and/or culture isolation. Spirochetes were visualized in blood smears of both deer on days post-inoculation (DPI) 6, 8, 12 and one deer on DPI 15. Whole blood collected from deer tested PCR positive starting on DPI 4 and remained positive as long as DPI 28. Both deer developed antibody titers of >64, with a maximum IFA titer of 1024. The organism was reisolated from the blood of both deer on DPI 6 and one deer on DPI 12. All isolation attempts from mice, calves, or dogs were negative, although one of seven mice was transiently PCR positive. Mice and dogs developed an IFA titer > or =64, while calves lacked a detectable antibody response. These preliminary experimental infection trials show that white-tailed deer are susceptible to infection with B. lonestari and develop a spirochetemia following needle-inoculation, while C3H mice, calves, and dogs do not. Results suggest that deer may serve as a vertebrate reservoir host. Tick transmission studies are needed to confirm that this organism can be maintained in a natural cycle involving deer and A. americanum.