Bartonellosis: An emerging disease?

Editor's Note: In a continuing series of articles, DVM Newsmagazine has teamed up with the American College of Veterinary Internal Medicine, (ACVIM) to bring you the latest in research abstracts on a variety of topics. Every month, an ACVIM diplomate will summarize, in abstract form, the latest research in specialty fields. These articles are coordinated with the help of Dr. Ron Lyman, Ft. Pierce, Fla.

Bartonellosis may be a very important infectious disease just on thehorizon in veterinary medicine. Its place in human medicine is becomingmore firmly established on a daily basis. Will veterinary medicine soonfollow?

The Bartonella genus consists of facultative, intracellular, gram-negative,argyrophilic bacteria. These organisms tend to adhere to red blood cellsand endothelial cells. These tendencies may contribute to the organism'sability to invade nearly every organ of the body. In people, a multitudeof clinical syndromes have now been associated with this bacteria (see Table1). The organism has been found in North America, Europe, Asia, Australia,South America and the Middle East.

Most commonly we think of cat scratch disease, which is seen in immunocompetentindividuals almost invariably associated with a feline encounter. Therehave been cases where cats have not been involved. It appears that the catflea is involved in the spread of the bacteria. The organism has been foundin the flea and flea feces. Few cases of humans bitten by fleas have beendocumented. In all likelihood, cats transmit the bacteria to people by depositingflea feces into human skin via a scratch or bite. People have developedthe disease living with cats that have been declawed. The possibility offlea excrement in the environment entering an injury to a person's skindoes exist. Recently, a Bartonella species was isolated from Ixodes scapularisticks found on a cat living with a Bartonella infected woman in New Jerseyand the dog flea in Japan. The significant prevalence of Bartonella seropositivityalong with positive titers to E. canis and B. canis make the spread by othertick species likely.

The table of disease found in man contains many that are found in bothdogs and cats. Could Bartonella cause some of these in our patients? Bartonellavinsonii was first isolated from a dog with endocarditis in 1993. At leasteight other dogs with culture negative endocarditis and high antibody titersto B. vinsonii have been found. The organism was implicated as a cause ofpyogranulomatous lymphadenitis in a dog. A large number of confirmed casesis lacking. However, it appears that this organism can cause myocarditisand resultant arrhythmias. In cases of endocarditis - lameness, bone painand fevers may occur. Recent serologic evidence points to the likelihoodof this organism contributing to the development of hemolytic anemias, non-regenerativeanemias, cutaneous vasculitis resulting in dermatological lesions, polyarthritis,anterior uveitis and meningoencephalitis. Possible laboratory abnormalitiesmay include neutrophilic leucocytosis, thrombocytopenia and anemia. Eosinophiliaand monocytosis have been found. Isolation of the organism is extremelydifficult. PCR and serology are the useful diagnostic tools. There appearsto be a strong association of infection with Bartonella and tickborne diseasesin the dog. A seroprevalence study involving close to 2,000 sick dogs fromthe southeastern United States showed 3.6 percent of the dogs were positivefor B. vinsonii. Risk factors included heavy tick and flea exposure andliving in a rural environment. However, in serum samples infected with E.canis or B. canis, 36 percent and 52 percent were reactive to B. vinsonii,respectively.

Currently, many cats around the country are being tested for Bartonellaspecies. Prevalence rates in healthy cats vary from 7 percent in Minnesotato 17 percent in New Jersey, to 28 percent in Virginia. Controlled definitivestudies have not been established. However, a possible association of Bartonellaand a host of disease processes are becoming evident. Apparent Bartonellaassociated diseases including gingivitis, stomatitis, oral ulcers, conjunctivitis,sinusitis, fever, lymphadenopathy, uveitis and chorioretinitis. In somepopulations, almost 60 percent of affected animals are strongly positivefor Bartonella. Cats with myocarditis, inflammatory bowel disease and neurologicabnormalities are testing positive. Risk factors are environment (shelteror stray), multicat household, fleas, living with a Bartonella positivecat or a person with cat scratch disease.

Therapeutic options include azithromycin, tetracycline and enrofloxacin.Antibody titers decline slowly and it may be six months before significantfalls are detected.

It may very well be that we are on the cutting edge of finding the causativeagent of some of our "idiopathic" diseases. Our job is to investigatethe possibility of Bartonella as a culprit.

Transdermal medications

Several talks were given regarding the use of transdermal medications.Unfortunately, the scientific data supporting the use of delivering medicationin this form is miserably deficient. Currently, there are at least fourstudies under way investigating diltiazem, odansetron, amitryptyline, busperoneand EMLA. There is no available data from these studies. The take home messageis the use of these formulations should be limited to drugs that have ameasurable therapeutic endpoint. This could be heart rate, blood pressure,digoxin level or thyroid level for example. Factors that must be consideredare:

1. Is there a large margin of safety?

2. What is the shelf life?

3. Is the same vehicle used every time?

4. What is the appropriate dose?

5. Can you risk a therapeutic failure?

Until more data is available, practitioners need to proceed with cautionwhen recommending medications administered by the transdermal route.

Table 1

Newly described human disease:

* Inflammatory bowel disease

* Mononucleosis-like syndrome

* Pulmonary infiltrates

* Meningoencephalitis

* Arthralgia

* Juvenile arthritis

* Cutaneous rash-Henoch-Scheniein purpura

* Cutaneous granuloma annulare

* Disciform keratitis

Previously described human diseases:

* Cat scratch disease

* Bacillary angiomatosis

* Bacillary peiosis

* Febrile bacteremia

* Lymphadenopathy

* Endocarditis

* Vegetative valvular disease

* Uveitis

* Neurological disorders

* Anemia

* Neuroretinitis

* Osteomyelitis