Detection of Zoonotic Bartonella Pathogens in Rabbit Fleas, Colorado, USA

Shingo Sato; R. Jory Brinkerhoff; Erin Hollis; Shunta Funada; Avery B. Shannon; Soichi Maruyama

Disclosures

Emerging Infectious Diseases. 2020;26(4):778-781. 

In This Article

Conclusions

We detected DNA of 3 zoonotic Bartonella species among the 105 rabbit fleas we tested for this study; overall Bartonella prevalence in fleas was 21.9% (23/105), which is comparable to previous prevalence estimates from rabbit fleas in Europe.[7,9] This study had several noteworthy findings: B. alsatica DNA was detected in North America, and carnivore-associated Bartonella species occurred in rabbit fleas. These findings highlight the complexity of pathogen–vector–host associations and demonstrate why vector ecology is necessary for elucidating the evolution and enzootic transmission of vectorborne pathogens. Since B. alsatica was described in 1999,[2] its DNA has been detected not only in European rabbits (Oryctolagus cuniculus) in Spain[8] but also in rabbit fleas (Spilopsyllus cuniculi and Xenopsylla cunicularis) collected in France[7] and Spain[9] and has been associated with human disease in France.[3–6] In 2019, detection of B. alsatica DNA was reported in cat fleas (Ctenocephalides felis) infesting cats and dogs in the United Kingdom.[12]

A recent study reported ftsZ and nuoG sequences with ≈95% similarity to B. alsatica from the spleens of spiny rats (Thrichomys fosteri) in Brazil,[13] the only previous published report of B. alsatica in the Americas. The B. alsatica sequences in our study were more similar to the B. alsatica type strain than were the putative B. alsatica sequences detected in Brazil. However, the B. alsatica sequences in our study were not identical to the type strain, suggesting that divergent B. alsatica strains may be circulating in the Americas. Further sampling of lagomorphs and their ectoparasites throughout North and South America is necessary to determine the geographic extent of B. alsatica, as well as its genotypic variation and evolutionary history.

We can conclude that both C. inaequalis and E. glacialis fleas are able to acquire Bartonella DNA and that blood-feeding is a likely mode of Bartonella acquisition, based on the observation that multiple fleas from the same host tested positive for Bartonella DNA. The detection of carnivore-associated Bartonella species in rabbit fleas was unexpected; typical reservoirs for B. rochalimae and B. v. subsp. berkhoffii are wild carnivores such as coyotes, foxes, raccoons, and skunks. However, B. rochalimae or B. rochalimae–like bacteria were found in the blood of brown rats (Rattus norvegicus) captured in Taiwan and in California, USA.[14] Thus, B. rochalimae might have the potential to infect rodents as well as carnivores. Both rabbit flea species sampled in this study have been recovered from wild carnivore species in our study system and thus could serve as bridge vectors between carnivores and rabbits.[10] In Europe, rabbit fleas have also been collected from carnivores,[15] suggesting potential lagomorph–carnivore B. alsatica transmission in other systems as well.

Yersinia pestis, another fleaborne zoonotic agent that periodically causes epizootic events in our system,[10] may spill over into amplifying hosts from putative reservoirs (mammalian, flea, or both) or from environmental sources. Flea and Bartonella (Table 2) exchange between lagomorphs and carnivores suggests that Y. pestis could also jump among these groups of mammals. Moreover, desert cottontails co-occur with black-tailed prairie dogs (Cynomys ludovicianus), a species associated with epizootic Y. pestis emergence, and flea exchange between desert cottontails and prairie dogs has been described.[10] Given our findings, it is apparent that desert cottontail rabbits are associated with multiple zoonotic Bartonella species, including B. alsatica, which had not been previously recorded in North America, and that wild lagomorphs may contribute to the maintenance and transmission of several vectorborne zoonoses.

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