Rickettsia typhi Is Still Present in Southeastern Georgia, USA

Background: Rickettsia typhi is the causative agent of murine typhus, a zoonotic disease that is sustained in nature primarily through the rat to rat flea transmission cycle. Southeastern Georgia was historically associated with outbreaks of this disease; however, its current occurrence in Georgia is unknown. Rickettsia felis, another human pathogen, is primarily associated with cat fleas and can often be found on cats, dogs, and opossums. The purpose of this study was to characterize rickettsial bacteria that are associated with fleas infesting companion and wild animals in Southeastern Georgia.

Methods: Fleas were collected from companion cats, dogs, and from opossums and a cotton rat that were trapped in woodland nonhuman inhabited areas in Bulloch, Fulton and Warren Counties, Georgia in 2011-2014. The fleas were identified to species and the DNA was extracted using Qiagen DNeasy kit according to the manufacturer’s directions. Flea DNA were individually tested using TaqMan assays specific for R. typhi and R. felis.

Results: Only Ctenocephalides felis were collected from cats. Dogs were infested with C. felis and Pulex simulans (n=2). Opossums were mainly infested with Polygenis gwyni (n=68) while only a few C. felis (7) and Orchopeas howardi (3), were found. R. typhi DNA was detected in 4% of P. gwyni and 12% of C. felis tested, R. felis DNA was detected in 76.61% of C. felis and 14% of P. gwyni tested.

Summary and Conclusions: We demonstrated that R. typhi is still present in the area and that there is a prevalent circulation of R. felis in C. felis in Georgia. This is the first report of this agent in P. gwyni. Since R. typhi is still present it may be associated with other reservoir hosts, outside of its classic urban ratrat flea cycle. Our data suggests that companion animals may become infested when coming in contact with sylvatic animals and vice versa.