Rickettsia typhi, Bartonella henselae and related zoonotic agents in fleas from domestic cats (Felis catus) from the Rio Grande Valley, Texas

Background Flea-borne rickettsiosis and bartonellosis are emerging diseases in humans and animals. There is increasing concern for the emergence of Rickettsia typhi (agent of murine typhus or flea-borne typhus) in humans of southern USA, for which cats are key reservoirs and cat fleas ( Ctenocephalides felis ) serve as the vector. Similarly, multiple species of Bartonella have cats as natural hosts and fleas as vectors, leading to varied disease outcomes in humans, including cat scratch disease and neurobartonellosis. Methods To investigate the ecology of Rickettsia and Bartonella pathogens, we studied 167 predominantly stray cats ( Felis catus ) from the Rio Grande Valley in south Texas. Fleas were collected, identified morphologically and confirmed molecularly. DNA from fleas was tested for Rickettsia and Bartonella using PCR and Sanger sequencing of multiple gene targets. Additionally, DNA from blood of all cats and tissues from a subset of cats were assayed for infections. Results Flea infestation prevalence of cats was 83% - higher in male vs. female cats - yielding 721 fleas, predominantly C. felis with 2 Echidnophaga gallinacea and 1 Pulex sp . Flea burden was a significant predictor of Rickettsia infection in fleas. Candidatus Rickettsia senegalensis was identified in 28 flea pools (20% of all pools) and Rickettsia typhi in 6 flea pools (4%). Bartonella henselae was identified in 59 flea pools (42% of all pools) and blood from 37 cats (22.2%); Bartonella clarridgeiae was detected in 3 flea pools (2% of pools) and blood from 1 cat (0.7%). Thirty cats had simultaneously Bartonella- positive fleas and blood. Rickettsia infection was positively associated with flea burden. Co-infections of Rickettsia and Bartonella in fleas occurred more commonly than expected by chance. Conclusions Cats and their fleas support robust transmission of R. typhi , B. henselae and related agents in south Texas with implications for veterinary and public health.