Three emerging vector-borne diseases in dogs and cats in the United States - Veterinary Medicine
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Three emerging vector-borne diseases in dogs and cats in the United States
Canine babesiosis, feline cytauxzoonosis, and canine bartonellosis are being diagnosed more often. Make surethat these diseases are on your differential diagnoses list and that you're current on the treatment options.


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Clinical disease

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.

Diagnosis

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 weeks).

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


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