Transmission of Rickettsia parkeri by the gulf coast tick, Amblyomma maculatum Koch

Amblyomma maculatum is the primary vector for Rickettsia parkeri, a Spotted Fever Group (SFG) rickettsia recently determined to be a human pathogen. Cotton rats and bobwhite quail are known hosts for immature stages of this tick. Their exact role in the ecology of R. parkeri, however, is unknown. To study feeding success we placed immature ticks directly onto individual animals of three potential host species: Carolina anoles, cotton rats, and Bobwhite quail (n=10 of each species). No ticks fed on anoles. Larvae that fed on rats and quail did not statistically differ in number of days to engorge. Nymphs took significantly longer to engorge on rats than on quail. Engorged larvae were not statistically different in weight, while nymphs that engorged on rats were significantly heavier. Engorged larvae and nymphs did not significantly differ in their molt success between hosts. To study transmission of R. parkeri to feeding ticks, we inoculated cotton rats and quail with cultured R. parkeri (Portsmouth). Four days post injection (dpi), nymphs were placed on animals (n=50 or 65). Ticks were allowed to feed for twelve days, after which engorged ticks were allowed to molt. At the adult stage, ticks were cleaned and split in half: one half was put in Vero culture and the other was DNA extracted and PCR tested. No culture was determined to have isolated R. parkeri. The ticks are currently being DNA extracted and PCR tested. Information from these studies is important in understanding the natural cycle of Rickettsia parkeri.