When dogs develop clinical abnormalities, such as fever, joint inflammation or a particular kidney diseases, veterinarians will often consider vector-borne diseases transmitted by blood-feeding ectoparasites like ticks, fleas, mosquitoes and sand flies.

Bartonella are bacteria transmitted by fleas, ticks, sandflies and other insects. They are small, obligate intracellular organisms that adhere and invade erythrocytes and endothelial cells of mammalian hosts, causing long lasting long-lasting presence of bacteria in the blood (bacteremia). The organisms are highly adaptive which enables them to persist within the cells of their mammalian hosts for extended periods. Over 30 species and subspecies of Bartonella have been identified. Many cause infections in animals, 15 are known to infect humans, with 9 of these capable of infecting dogs as well (B. clarridgeiae, B. elizabethae, B. henselae, B. koehlerae, B. quintana, B. rochalimae, B. v. berkhoffii, B. volans and B. washoensis).

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Bartonella infections produce a wide range of pathological signs, ranging from lymphadenitis, trench fever, cat scratch disease, fever of unknown origin to severe endocarditis. Worldwide, cat scratch disease (CSD) is the most commonly recognized zoonotic disease caused by Bartonella species. B. henselae and B. quintana cause severe systemic diseases in immunocompromised patients, such as bacillary angiomatosis and bacillary peliosis. Infections from Bartonella may look atypical and mimic a malignancy clinically as well as radiologically. They may masquerade as a lymphoma or squamous cell carcinoma. Finally, it has also been demonstrated that Bartonella stimulate cell growth and may lead to tumor formation. In addition to the association of Bartonella with malignancy, this bacterium has also been associated with rejection in transplant recipients.

In general, people with extensive arthropod exposure and animal contact had high infection rates (24–41%) of Bartonella species. Cats are the main reservoir for Bartonella henselae, B. clarridgeiae, and B. koehlerae and Bartonella bacteremia can be found in up to 50% of the domestic and feral cat populations in regions where fleas are common. Cats also can be coinfected with more than one Bartonella species. Domestic dogs are more likely to be accidental hosts, at least in nontropical regions.

Dogs infected with Bartonella species can develop lameness, endocarditis, granulomatous lymphadenitis, granulomatous rhinitis and peliosis hepatis (blood-filled cavities throughout the liver), lesions that have also been reported in association with human infection. Endocarditis associated with B. vinsonii occurs in large-breed dogs with a potential predisposition for aortic valve involvement. In addition to endocarditis, areas of severe myocardial inflammation can be found in dogs with B. vinsonii endocarditis. Potentially, myocarditis without endocarditis can result in cardiac arrhythmias, syncope, or sudden death. The complicating factor is that dogs may be infected at the same time with Ehrlichia, Babesia, and Bartonella species by Ixodes ricinus ticks that can simultaneously contain B. burgdorferi, Ehrlichia and Bartonella species. Recently, infection with a Bartonella species has been implicated in several cases of nosebleed in dogs.

The treatment needs to be long in duration (6 weeks to 3 months) and more than one antibiotic is needed. For long term therapy doxycycline and enrofloxacin in dogs and doxycycline and pradofloxacin in cats are used, until other antibiotics or antibiotic combinations are proven to be effective. A combination of two antibiotics with different modes of action, one achieving high blood concentrations and the other achieving high intracellular concentrations is needed to eradicate Bartonella infections.


  1. Candidatus Bartonella merieuxii, a Potential New Zoonotic Bartonella Species in Canids from Iraq
  2. Bartonella Infection in Animals: Carriership, Reservoir Potential, Pathogenicity, and Zoonotic Potential for Human Infection
  3. Concomitant cat scratch disease and squamous cell carcinoma in a cardiac transplant
  4. Treatment of Canine and Feline Bartonellosis. Ed Breitschwerdt DVM, Professor of Medicine and Infectious Diseases

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