For Veterinarians

Domestic pets are susceptible to infection with various species of Bartonella and can play a role in human infection. Bartonella henselae bacteremia has been documented in 30-40% of domestic and adopted shelter cats. Kittens showing evidence of infection were more likely to have a high bacterial load compared to young adult cats. Rates of seropositivity for Bartonella henselae vary by region, with 6% of cats showing evidence of exposure in Illinois compared to 33% in Florida. Cats may also harbor Bartonella clarridgeiae and (rarely) other Bartonella species. Cats become infected with Bartonella henselae from the bites of infected fleas or contact with infected blood; cats involved in cat fights or who have received blood transfusions are more at risk for infection.

Dogs may carry Bartonella vinsonii subsp. berkhoffii, Bartonella henselae, and other Bartonella species.  Bartonella infection is more likely to cause clinical symptoms in dogs compared to cats. Low seroprevalence in worldwide dog populations suggests that dogs are probably not a natural reservoir for B. vinsonii berkhoffii. It is not yet known whether dogs can transmit infection to humans. In addition to dogs and cats, numerous domestic and wild animals, including bovine, canine, human, and rodent species can serve as reservoir hosts for various Bartonella species.

Clinical Presentation

Cats

Naturally infected cats are primarily asymptomatic, subclinical carriers of Bartonella henselae. B. henselae infections in cats, also known as feline bartonellosis, may occasionally cause a self-limiting, transient, febrile illness that lasts for approximately 48-72 hours. Clinical symptoms of more serious infection, although rare, include fever, vomiting, lethargy, red eyes, swollen lymph nodes, and/or decreased appetite. Bacteremia can persist for months with clinical signs appearing when the cat is under stress (surgery or trauma) or concurrent with another disease.

Dogs

Dogs present with a wide range of clinical and pathologic abnormalities, including: fever, endocarditis and myocarditis, granulomatous lymphadenitis, cardiac arrhythmias, granulomatous rhinitis, and epistaxis. In both humans and dogs, Bartonella-associated endocarditis usually involves the aortic valve and is characterized by massive vegetative lesions.

Diagnostic testing

Bartonella infections in symptomatic pets should be confirmed by culturing the organism from blood or tissues such as lymph node or heart valve (in cases of endocarditis) or by amplifying Bartonella-specific DNA sequences from tissues using PCR. Serology using immunofluorescence antibodies (IFA) is the most sensitive diagnostic tool for diagnosing Bartonella exposure, but it is not useful as a means of predicting animals that may pose a public health risk to their owners, or identifying animals that require treatment.

Treatment

Doxycycline, amoxicillin, enrofloxacin, and rifampin given for a long duration (4-6 weeks) may be effective in reducing the level of bacteremia in the infected cat or dog. The ability of any antibiotic or antibiotic combination to completely clear B. henselae from the blood stream has not been established. Given the duration of treatment necessary to clear the bacteremia and the concern for development of antimicrobial resistance, treatment is recommended only for pets that have clinical symptoms.

Prevention and control

• Dogs should be placed on an effective oral or topical flea prevention product such as fipronil, methoprene, Imidocloprid, or permethrin to protect them from fleas and tick infestations.
• Permethrin should never be used on cats. Other oral or topical flea prevention products are safe when used as directed.
• An indoor lifestyle for cats is preferable in the prevention of Bartonella transmission, as this environment will reduce the risk of flea infestation and contact time with other stray cats.
• Discourage immunocompromised individuals from playing with or owning young cats.
• Advise against rough play with cats, particularly kittens and free-roaming feral cats, to prevent scratches. This is especially important for people who have weakened immune systems. All cat scratches should be washed promptly with soap and water.
• There are currently no vaccines available for cats or dogs against Bartonella spp.