Bartonella spp. Isolated From Wild and Domestic Ruminants in North America

Chao-chin Chang, Bruno B. Chomel, Rickie W. Kasten, School of Veterinary Medicine, University of California, Davis, California, USA; Remy Heller, Institut de Bactériologie, Université Louis Pasteur, Strasbourg, France; Katherine M. Kocan, College of Veterinary Medicine, Oklahoma State University, Stillwater, Oklahoma, USA; Hiroshi Ueno, School of Veterinary Medicine, Rakuno-Gakuen University, Ebetsu, Hokkaido, Japan; Kazuhiro Yamamoto, School of Veterinary Medicine, University of California, Davis, California, USA; Vernon C. Bleich, Becky M. Pierce, Ben J. Gonzales, Pamela K. Swift, California Department of Fish and Game, Bishop, Rancho Cordova, California, USA; Walter M. Boyce, Spencer S. Jang, School of Veterinary Medicine, University of California, Davis, California, USA; Henri-Jean Boulouis, Ecole Nationale Vétérinaire d'Alfort, 94704 Maison-Alfort, France Yves Piémont, Institut de Bactériologie, Université Louis Pasteur, Strasbourg, France

Disclosures

Emerging Infectious Diseases. 2000;6(3) 

In This Article

Conclusion

This is the first published report of isolation of Bartonella spp. from free-ranging wild ruminants and domestic ruminants in North America. Our results suggest that deer, elk, and domestic cattle are possible reservoirs of Bartonella spp. Selected bighorn sheep populations from California and New Mexico appeared to be free of Bartonella. The first report of infection of cattle with a Bartonella organism was made in 1934 by Donatien and Lestoquard, who proposed the name B. bovis or Haemobartonella bovis[21]. In 1942, Lotze and Yiengst also described Bartonella-like structures in American cattle[22]; however, their identifications of Bartonella-like structures were based only on the morphologic aspects of these organisms in red blood cells also infected with Theileria or Anaplasma, two well-known tickborne infections.

Partial sequencing analysis of the citrate synthase gene of the ruminant strains showed that they were all closely related to each other and to a feline strain, B. weissii. Further studies by DNA-DNA hybridization may determine if these strains are specific to ruminants but closely related to B. weissii, or if they are in fact B. weissii. If the ruminant strains are identical to B. weissii, the high prevalence (89%) of Bartonella bacteremia observed in beef cattle may indicate that ruminants are the main reservoirs of B. weissii, which is not commonly isolated from cats.

The prevalence of Bartonella bacteremia was high in beef cattle and mule deer, possibly related to exposure to potential vectors. Since fleas are rarely observed on cattle and tick infestation is common in both cattle and deer, ticks are a possible source of infection for ruminants[17]. Furthermore, Bartonella DNA has recently been demonstrated in a high percentage of ticks infesting roe deer in Europe[23,24]. The herd of beef cattle from the Sierra Nevada foothills, where tick infestation is common, has permanent access to open pastures. In contrast, the dairy cattle herd from the Central Valley has litle or no access to pastures and tick infestations are not commonly observed (R. BonDurant, pers. comm.). Therefore, geographic differences in the prevalence of Bartonella infection in California cattle herds warrant further investigation for possible tick transmission of Bartonella spp. among these animals.

PCR/RFLP analysis of the citrate synthase gene has been widely used for identification of Bartonella organisms to the species level[25,26,27]. We identified one PCR/RFLP profile for all the cattle isolates, but several profiles for deer and elk. This diversity by geographic location is of epidemiologic interest and warrants further investigation. Only one elk from southwestern Oregon had a strain with a similar PCR/RFLP profile to that of domestic cattle, suggesting that wild ruminants could be infected with Bartonella species that are not commonly shared with cattle.

Our findings also suggest that transmission of Bartonella may occur among cattle and wildlife, especially mule deer, which are more abundant in the western USA than elk and are more likely to be sympatric with cattle. Collection and analysis of ticks on wild animals and cattle and from the environment will be necessary to determine if ticks can be infected with Bartonella species. Whether Bartonella isolated from these ruminants are human pathogens are still unclear. The recent report of a cattle rancher who was infected with a new B. vinsonii subspecies[28] warrants further investigation to establish if these Bartonella species could be zoonotic and whether humans could potentially be infected by tick bites during work or recreation.

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