Rickettsia typhi, Bartonella henselae, and related zoonotic agents in fleas from domestic cats (Felis catus) from the Rio Grande Valley, Texas
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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 polymerase chain reaction (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 83.23% (95% CI 76.69–88.56)—higher in male versus female cats—yielding 721 fleas, predominantly C. felis with two Echidnophaga gallinacea and one 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; 95% CI 13.72–27.59) and Rickettsia typhi in 6 flea pools (4.29%; 95% CI 1.59–9.09). Bartonella henselae was identified in 59 flea pools (42.14% of all pools; 95% CI 33.85–50.77) and blood from 37 cats (22.16%; 95% CI 16.11–29.22); Bartonella clarridgeiae was detected in 3 flea pools (2.14% of all pools; 95% CI 0.44–6.13) and blood from 1 cat (0.6%; 95% CI 0.01–3.29). A total of 30 cats had simultaneously Bartonella- positive fleas and blood. Rickettsia infection was positively associated with flea burden. Coinfections of Rickettsia and Bartonella in fleas occurred more commonly than expected by chance.
Conclusions
The infection of fleas from cats in south Texas with R. typhi and multiple Bartonella species, in addition to Bartonella infections in the host cats, suggest that public health surveillance for these emergent zoonoses should include a focus on vectors and potential feline reservoirs.
