Bartonellosis: An emerging and potentially hidden epidemic? - Veterinary Medicine
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Bartonellosis: An emerging and potentially hidden epidemic?
Bartonella species, their animal hosts, potential vectors, and sequelae of infection are being identified at a snowballing rate. A new diagnostic test may help DVMs and MDs come together to better understand these infections in their patients.



In my opinion, physicians and veterinarians need to come together regarding bartonellosis, because it appears to be an important and under-recognized zoonosis. Depending on their immune competence, people with bartonellosis exhibit tremendous differences in disease expression. And with regard to immunocompetence, we have to consider not only people with severe immunosuppressive illnesses such as infection with HIV, but also pregnant women, children, geriatric people, transplant recipients, and patients treated with immunosuppressive drugs. Furthermore, diagnostic test sensitivity for documenting infection with this genus of bacteria is extremely poor, and based upon recent experience in our laboratory, patient response to treatment is frequently incomplete.

Endocarditis can be induced by a spectrum of Bartonella species in dogs and human patients and is the best example of documented disease causation for this genus. Historically, Bartonella species have been a cause of culture-negative endocarditis in people and dogs because the diagnostic methods that microbiology laboratories used were not adequate to isolate these bacteria. Now, by using specialized techniques, a spectrum of Bartonella species are being identified in research and diagnostic laboratories in different parts of the world—in heart valves or in blood cultures from people and dogs with endocarditis.12 And what's important for physicians and veterinarians to recognize is that some of these Bartonella species are found in cats, dogs, rats, ground squirrels, and rabbits. In 1992, two Bartonella species were known to exist, and in 2009, over 26 named or candidatus species exist.


Bartonella species are present in a multitude of animal species. One of the most recently identified Bartonella species, Bartonella australis, was found in kangaroos.13 Unexpectedly, 82% of beef cattle in North Carolina have Bartonella bovis in their blood.14 My laboratory can isolate a Bartonella species from one or two out of three feral cats in North Carolina,15 and other laboratories around the world have documented similar levels of bacteremia in flea-infested cats.

Another important point for physicians and veterinarians to consider is that many of their patients and clients have pocket pets, some of which tend to scratch and bite. Unfortunately, numerous Bartonella species have been identified in the blood of various rodent species. For example, the overall prevalence was 26% in the population of wild and captive animals brought to Japan to be sold as pocket pets.16 The human medical literature in the United States reveals case reports of previously healthy people with no evidence of louse exposure and a history of cat exposure who presented to their physicians for evaluation of lymphadenopathy or seizures and were found to be infected with Bartonella quintana.17 More recently, our laboratory isolated B. quintana from cats and from a woman who was bitten by one of those cats.17

Another reason why I think the One Medicine initiative (veterinarians and physicians working together to fight disease) is important: In reviewing the human literature, as it relates to B. quintana, it told me, as a veterinary internist, what I should be looking for in my canine patients if I suspect that this organism is causing disease. And vice versa: I would suggest that physicians review data and observations that veterinarians are generating in regard to this genus of bacteria, because clearly some of us now are much more concerned about the genus Bartonella than anyone is at the National Institutues of Health (NIH) or Centers for Disease Control and Prevention (CDC).


Bartonella species can induce a number of what I think are fairly well established pathologies in either dogs or people.18

The first dog we cultured Bartonella species from was a 3-year-old female Labrador retriever called Tumbleweed. Briefly, the dog had a history of a positive antinuclear antibody test result and had been receiving increasing doses of immunosuppressant drugs. Within a one-year time frame, Tumbleweed developed polyarthritis, seizures, vasculitis, epistaxis, and aortic and mitral valve endocarditis. We ultimately identified the first Bartonella species infection in a dog, and the novel organism was named Bartonella vinsonii subspecies berkhoffii.19

Cases similar to Tumbleweed's have occurred in people. For example, Duke University Medical Center and the Mayo Clinic have described patients who were treated with immunosuppressant drugs, based on finding antineutrophil cytoplasmic antibodies, and subsequently developed Bartonella species endocarditis.20,21

So we're seeing that what's occurring in people is also occurring in dogs—for example, about 80% of people and about 80% of dogs have endocarditis selectively involving the aortic valve. And based on the veterinary literature, physicians may want to put bartonellosis on their differential lists for children with unexplained epistaxis.19,22,23


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