Ron Hines DVM PhD 4/24/06

In the last thirteen years veterinarians have begun to recognize that a group of gram negative bacteria called Bartonella are a common cause of a variety of disease in cats. All diseases caused by this organism involve chronic inflammation of tissues called lymphocytic plasmacytic granulomatous inflammation. For years, veterinarians have been faced with eye disease in cats the cause of which remained unknown. Within the last few years, Dr. William Hardy has found that Bartonella are responsible for many of these perplexing cases. Unfortunately this organism is very hard to isolate and grow in the laboratory.

Bartonella organisms are known to cause cat scratch fever in humans and cats (see my article on Bartonellosis http://www.2ndchance.info/catscratch.htm. Dogs can also become infected. Cats with this disease can harbor the organism for years without signs of sickness. Fleas and ticks spread the organism from cat to cat. Fleas and ticks also have the potential to transmit the organism from pets to their owners. Some sources estimate that a one in five cats is a carrier of Bartonella. In addition to cats, five to ten percent of pet owners who contract cat scratch fever from their pets develop eye inflammation. This inflammation takes many forms. All portions of the eye can be affected by the organism. One or both eyes can be affected and even the eyelids may be involved. When the anterior portion of the eye is inflamed the condition is called uveitis. When the cornea is inflamed the condition is called keratitis and when the membranes that surround the eye are affected it is called conjunctivitis. When any of these syndromes occur we identify the cause in less than half the cases. Until recently, we assumed that many of the cases of uveitis were due to toxoplasmosis. We made this assumption based on antibody levels to toxoplasma in the pet or human involved. However, the presence of antibody to toxoplasma does not necessarily mean that the eye problem is related, and we now think that many of these cases are probably due to Bartonella.

The antibody test we use to detect Bartonella infection is called the Western Blot. Using this test, it appears that about twenty percent of cats in the United States carry Bartonella. In another study, of cats showing eye inflammation, 67.5% were positive for Bartonella using this test.

Recent studies have shown that several antibiotics are successful in eliminating Bartonella infection. The least expensive of these antibiotics, doxycycline, (5mg pound given orally every 12 hours of 6 weeks) eliminated the infection. When using doxycycline capsules or tablets it is important to wash the pills down the cat’s throat with liquids to prevent ulceration and inflammation of the esophagus. Another antibiotic, azithromycin (Zithromax) is also effective at 5mg/pound body weight given once a day for 21 days. Azithromycin is currently the drug of choice because it will kill mycoplasma which may also be present. Rifampin (Rifampicin, Rifadin, Rimactane), an antibiotic often used to treat human tuberculosis is effective at 5mg/pound once a day for 21 days. While on one of these medications, it is wise to administer corticosteroid and atropine-containing’; eye drops to the cat to inhibit scaring and pathological changes in the structure of the eye. Non-medicated eye drops help correct dry eye, which occasionally occurs, with azithromycin administration. When treatment is successful, antibody, as measured by the Western Blot test, will begin decreasing in six month.

Journal of the American Animal Hospital Association Jan/Feb pp 6-12 2004

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