The full spectrum of canine disease caused by Bartonella species has yet to be elucidated. Infective endocarditis is the best-characterized disease associated with canine bartonellosis.14,20,81,82 The manifestations of infective endocarditis caused by Bartonella species do not appear to be different from those caused by other bacteria. The most common presenting complaints include
lameness and dyspnea, presumably due to immune-mediated polyarthritis and congestive heart failure, respectively. Physical
examination findings in dogs with endocarditis caused by bartonellosis typically include heart murmur, fever, and dyspnea,
with many dogs presenting in congestive heart failure.20
In the cases reported in the literature, the most common hematologic abnormalities include mild thrombocytopenia, leukocytosis,
and anemia. Common serum chemistry profile abnormalities include mild hypoalbuminemia, mild to moderately increased liver
enzyme activity, and azotemia.20 Unfortunately, most cases reported have not clearly defined whether or not the azotemia was of renal or prerenal origin.
Proteinuria was the most common abnormal finding on urinalysis.
Many other conditions and abnormalities have been associated with bartonellosis in dogs, but a cause-and-effect relationship
has not been clearly established.83 Some of these findings include granulomatous lymphadenitis, granulomatous rhinitis, granulomatous hepatitis, and peliosis
hepatis.19,80,84,85 A recent study in dogs that had anti-Bartonella species antibodies reported thrombocytopenia and neutrophilic leukocytosis in 50% of the dogs.83 Further studies are needed to fully elucidate the clinical manifestations associated with bartonellosis in dogs.
Serology, PCR testing, and culture are the three most widely available tests for canine bartonellosis. Serology is only commercially
available for B. vinsonii and B. henselae and is performed by using an IFA-based test or a Western blot test. Both tests appear to be sensitive for detecting exposure
to Bartonella species, but the presence of antibodies against Bartonella species antigens may not always correlate with current infection. The PCR test detects a specific fragment of Bartonella species DNA and is indicative of current infection, but false negative results may occur when bacteria are present in low
numbers. Culture is highly specific, but the sensitivity is poor because of the low numbers of circulating bacteria and their
fastidious nature, which makes them difficult to grow. Because both the true prevalence of bartonellosis in the canine population
and the full spectrum of disease caused by these organisms are unknown, interpret positive test results with caution in regard
to whether bartonellosis is the cause of any underlying disease.
Treatment and prevention
The best treatment for canine bartonellosis has yet to be established, as no formal studies have been performed to determine
the efficacy of antibiotic treatments against Bartonella species in dogs. Because of experience with treating bartonellosis in other species, dogs have been treated with a variety
of antibiotics, including amoxicillin trihydrate-clavulanate potassium, azithromycin, doxycycline, and enrofloxacin.83 In many of the cases reported, the clinical signs resolved after antibiotic treatment, but whether this is because the bartonellosis
resolved is difficult to determine because of concurrent treatments and diseases. Many clinicians are recommending treatment
with azithromycin (5 to 10 mg/kg orally once a day for five days, followed by 5 to 10 mg/kg orally every other day for six
Since the natural route of transmission for Bartonella species in dogs is unknown, the best method of prevention is unknown. In one study, tick exposure and outdoor environments
were associated with bartonellosis, as was concurrent seroreactivity against several tick-borne diseases such as ehrlichiosis
and babesiosis.15 These factors implicate tick transmission for bartonellosis, so acaricides and daily tick removal are recommended.
Bartonella species are recognized as potential zoonotic pathogens, so proper client education is important when bartonellosis is diagnosed
in a dog. A few cases of human bartonellosis have occurred in which the only animal contact was with a dog.86,87 The possible modes of transmission between dogs and people are unknown, but avoiding bites and scratches and providing appropriate
flea and tick control to dogs should be recommended.
Adam Birkenheuer, DVM, PhD, DACVIM (internal medicine)
Department of Clinical Sciences
North Carolina State University
College of Veterinary Medicine
Raleigh, NC 27607