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June 01, 2021

Bartonellosis: A zoonosis hidden in plain sight

The disease is one of many that veterinarians can and do get from animals
Published on May 12, 2021

Dr. Hilary Lucero always had seasonal allergies, but now it seemed like her hay fever had gone haywire.

It was spring 2018, and Dr. Lucero, a small animal veterinarian in Arizona, had symptoms of skin flushing, shortness of breath, heart racing, and eyelid swelling. After seeing multiple doctors, she suspected the underlying cause might be Bartonella infection. She was tested and had detectable titers of antibodies against two Bartonella species.

Dr. Lucero improved with treatment but got worse midway through and needed a few rounds of intravenous antimicrobials. She later suspected that she might also have been infected with Babesia, a tick-borne parasite, and tested positive. With additional treatment, she now feels almost completely recovered.

After her experience, Dr. Lucero wants veterinarians to be aware of the hidden and emerging zoonotic diseases that they can contract at and outside of work, along with the more obvious but often overlooked zoonoses.

Kitten with claws extended


Veterinarians can and do contract many zoonoses from their animal patients, including bartonellosis—particularly cat scratch fever caused by B henselae, carried by cats and cat fleas.

A study published in 2014 in the journal Vector-Borne and Zoonotic Diseases found DNA from at least one Bartonella species in 28% of 114 veterinarians and veterinary technicians. Because only a single blood sample was taken from each participant, the true prevalence could have been higher given the relapsing nature of Bartonella bacteremias. The species could be determined for 27 personnel, with B henselae in 15, B vinsonii subsp berkhoffii in seven, B koehlerae in six, and a B volans–like sequence in one.

Among Bartonella-positive subjects, 70% described headaches, compared with 40% of Bartonella-negative subjects. About 68% of Bartonella-positive subjects reported irritability, compared with 43% of Bartonella-negative subjects.

The No. 1 thing in fleas that could make you sick as a veterinarian or the owner is actually Bartonella. We think about it as cat scratch fever, but it actually gets on their claws from the flea dirt.

Dr. Michael Lappin, professor of infectious disease, Colorado State University College of Veterinary Medicine & Biomedical Sciences.

Bartonella and beyond

“A healthy pet without parasites is a minimal danger to human health,” according to Dr. Michael Lappin, a professor of infectious disease at the Colorado State University College of Veterinary Medicine & Biomedical Sciences.

The statement was on a slide for his presentation, “Hot Topics in Zoonoses,” during the joint virtual congress of the World Small Animal Veterinary Association and Federation of European Companion Animal Veterinary Associations in late March.

“The No. 1 thing in fleas that could make you sick as a veterinarian or the owner is actually Bartonella,” Dr. Lappin said. “We think about it as cat scratch fever, but it actually gets on their claws from the flea dirt,” or frass.

Dr. Lappin pointed to guidelines from the Companion Animal Parasite Council as a resource for controlling cat fleas, Ctenocephalides felis, and other pet parasites. Dr. Lappin, who is chair of the WSAVA One Health Committee, said WSAVA Companion Animal Zoonosis Guidelines are forthcoming in 2021.

Dr. Lappin also chaired the panel for the 2019 AAFP Feline Zoonoses Guidelines from the American Association of Feline Practitioners. According to the guidelines: “It is known that Bartonella species (particularly Bartonella henselae), the cause of cat scratch disease, peliosis hepatis, bacillary angiomatosis, bacterial endocarditis and a number of other human inflammatory syndromes such as polyarthritis, are present in the oral cavity, on the skin and on the claws of cats with Ctenocephalides felis infestations. Veterinary healthcare providers may be at greater risk of development of Bartonella species–associated syndromes from exposure to cats or infected C felis.”

Also according to the guidelines, “Currently, no drugs can consistently eliminate the Bartonella species carrier state from healthy cats and antibiotics like azithromycin can rapidly select for resistant strains.” The guidelines continue, “However, in some circumstances the veterinarian and physician may choose to test cats in contact with immunosuppressed people in a family or those with clinical manifestations of bartonellosis.”

The AAFP guidelines also address a range of other feline zoonoses. The National Association of State Public Health Veterinarians offers the Compendium of Veterinary Standard Precautions for Zoonotic Disease Prevention in Veterinary Personnel to cover the broad spectrum of zoonoses faced by veterinary clinic staff members.

There are more than 50 zoonotic diseases of importance in the United States, according to the 2015 edition of the compendium. The compendium lists some of the documented zoonotic infections in veterinary personnel as bartonellosis, cryptosporidiosis, dermatophytosis, leptospirosis, methicillin-resistant Staphylococcus aureus infection, plague, psittacosis, Q fever, salmonellosis, and sporotrichosis.

Alongside the compendium, the NASPHV offers the Model Infection Control Plan for Veterinary Practices. In 2018, the American Animal Hospital Association came out with the first AAHA Infection Control, Prevention, and Biosecurity Guidelines.

Dr. Breitschwerdt in the lab
Dr. Ed Breitschwerdt, a professor of internal medicine and Bartonella researcher at North Carolina State University College of Veterinary Medicine, works with students and researchers at the Intracellular Pathogens Research Laboratory. He co-founded Galaxy Diagnostics to offer Bartonella testing for humans and animals, with the tests for cats and dogs also available through a partnership with Idexx Laboratories. (Courtesy of Idexx)

Canaries in the coal mine

Dr. Ed Breitschwerdt, a professor of internal medicine at North Carolina State University College of Veterinary Medicine, devotes much of his research to Bartonella species and bartonellosis in animals and humans. He was an author of the paper on Bartonella in veterinary personnel—“Detection of Bartonella species in the blood of veterinarians and veterinary technicians: A newly recognized occupational hazard?”—which looked at attendees of the North American Veterinary Conference.

Among the types of bartonellosis in humans, veterinarians and nonveterinarians alike most frequently develop cat scratch disease, which is definitively associated only with B henselae, Dr. Breitschwerdt said. Dog bite transmission of Bartonella has been reported in humans, but dogs don’t maintain a high level of bacteremia like cats do. Veterinarians also have been infected with Bartonella through needle sticks.

Dr. Breitschwerdt started out studying Bartonella in cats. In 1993, his laboratory was the first to document bartonellosis in a dog. His team went on to find Bartonella in horses, cattle, and even marine mammals.

When Dr. Breitschwerdt spoke about his work at veterinary conferences, he said, “I started having veterinarians come up to me and say: ‘Gee, I have the same problems as the dogs you’re describing. Could you test me?’”

The Bartonella organism is extremely difficult to culture for testing. Dr. Breitschwerdt’s team tried an insect-based growth medium, which worked, to his amazement. The test was validated in dogs, and then the team started using the technique to test veterinarians.

Veterinarians are the canaries in the coal mine by which physicians will ultimately understand human bartonellosis.

Dr. Ed Breitschwerdt, professor of internal medicine, North Carolina State University College of Veterinary Medicine

Dr. Breitschwerdt couldn’t get anyone at veterinary or human diagnostic companies to take on the approach. Therefore, although he had no desire to start a business, he incorporated Galaxy Diagnostics in 2008, along with co-founder Ricardo Maggi, PhD, a molecular biologist at North Carolina State. Amanda Elam, PhD, whose expertise is in entrepreneurship, later became the chief executive officer.

Ctenocephalides felis
Cat fleas, Ctenocephalides felis, from cats contain multiple pathogens, with Bartonella species and Rickettsia felis being the most common, according to the 2019 AAFP Feline Zoonoses Guidelines from the American Association of Feline Practitioners.

Galaxy Diagnostics launched animal testing in 2009 and human testing in 2011, Dr. Elam said, and has improved on testing techniques through the years. The company offers Bartonella tests for cats and dogs, with the tests also available through a partnership with Idexx Laboratories. On the human side, Galaxy Diagnostics expanded from Bartonella testing to testing for multiple flea- and tick-borne diseases.

Dr. Elam said, “When veterinarians go to the doctor with a suspected vector-borne infection, they actually know more than their doctor.” Veterinarians have told her that they have gone to multiple physicians who won’t test them. Dr. Elam thinks physicians should screen for vector-borne disease before proffering a diagnosis of autoimmune disease.

Dr. Breitschwerdt said, “Veterinarians are the canaries in the coal mine by which physicians will ultimately understand human bartonellosis.”

In terms of prevention, he said, veterinarians should realize that Bartonella can infect almost every cell, so veterinarians could become infected if they cut themselves while performing surgery on a liver or are exposed to pathological effusions or other body fluids.

Avoiding bites and scratches is a recognized method for preventing Bartonella infection but is not always possible. Dr. Breitschwerdt advises veterinarians to wash out any bite or scratch immediately and preferably record in a personal medical record that a bite or scratch has occurred so they don’t forget about it if they develop symptoms later.

Parting thoughts

Dr. Lucero, the small animal veterinarian with Bartonella and Babesia infections, said: “Preventing these infections is a better option than trying to treat them. A one-health approach to this is focusing on flea and tick prevention for animals and seeking care from knowledgeable providers when exposure does happen. Bartonella and Babesia can be a much bigger problem in healthier individuals than originally thought, and further research and investigation is needed. Like SARS-CoV-2, we are still in the process of figuring everything out.”

Bartonella species in cats and humans

The 2019 AAFP Feline Zoonoses Guidelines from the American Association of Feline Practitioners list Bartonella species among potential scratch-, bite-, or exudate-associated zoonotic agents of cats. The guidelines identify the following principal clinical syndromes from Bartonella infection in cats and humans:

  • Cats: subclinical infection, fever, hyperglobulinemia, uveitis, lymphadenopathy, and others.
  • Humans, immunocompetent: focal lymphadenopathy, fever, encephalopathy, osteomyelitis, polyarthritis, and headaches.
  • Humans, immunocompromised: bacillary angiomatosis, bacillary peliosis, and others.

The guidelines also list Bartonella species under flea-borne disease because B henselae, B koehlerae, and B clarridgeiae are transmitted among cats by cat fleas, Ctenocephalides felis.

“There are other Bartonella species with zoonotic implications,” according to the guidelines. “Cats generally develop a higher level of bacteremia than dogs and so are epidemiologically linked more frequently to human disease. The vectors are unknown for some Bartonella species.”

Resources

The Companion Animal Parasite Council’s General Guidelines for Dogs and Cats.

The 2019 AAFP Feline Zoonoses Guidelines from the American Association of Feline Practitioners.

The Compendium of Veterinary Standard Precautions for Zoonotic Disease Prevention in Veterinary Personnel from the National Association of State Public Health Veterinarians.

The AAHA Infection Control, Prevention, and Biosecurity Guidelines (PDF) from the American Animal Hospital Association.

Galaxy Diagnostics offers testing for Bartonella infection in animals and testing for Bartonella infection and other flea- and tick-borne diseases in humans. The company has a webinar available on “Understanding Bartonellosis: A One Health Perspective,” sponsored by the One Health Commission and North Carolina State University College of Veterinary Medicine.