Bartonella-Related Eye Disease In Cats – Bartonellosis

Ron Hines DVM PhD

Other Forms Of Bartonella Disease

Other Reasons For Cloudy Pupils In Older Cats

Over the last fifteen years veterinarians have begun to recognize that a group of gram negative bacteria called Bartonella might be involved in a wide variety of diseases of cats. Bartonella are usually transferred from one cat to another by fleas (and rarely by ticks, scratches or bites). This particular bartonella, Bartonella henselae, is very well adapted to living in cats. So in most cats it appears to cause no health issues at all. But in some cats it associated with low grade chronic inflammation of tissues and organs in various locations in the cat’s body. Veterinarians suspect that cats with a strong, healthy immune system overcome these bacteria or keep the organism’s numbers low. While cats facing other concurrent health issues or stress have difficulty in doing so. For years veterinarians were faced with unexplainable eye inflammations in cats. (read here) Not too long ago, veterinarians realized that Bartonella might be at the root of some of these perplexing cases of uveitis and retinitis in cats, dogs and humans. (read here)

Sometimes the only signs we see in bartonella-infected cats are deep inflammations of the eye. Unfortunately bartonella are very hard to isolate and identify in the laboratory. Even when the organisms are successfully identified, so many apparently-normal cats carry bartonella that your veterinarian can never be 100% sure that they are the root cause of your cat’s eye problem. The most widely known disease caused by bartonella is cat scratch fever. Dogs can also become infected when bitten by a bartonella-carrying flea. Some sources estimate that one in five cats carry bartonella. That could be an exaggeration. Veterinarians really do not know. It is actually your cat’s lifestyle and the care you give it govern its risk of bartonella exposure. 

In addition to cats, 5-10 percent of people who contract cat scratch fever are said to develop eye inflammations. That inflammation can take many forms. I already mentioned the most serious cases, uveitis and retinitis, but any portion of the eye can be involved. When the cornea is inflamed the condition is called keratitis. When the membranes that surround the eye are affected it is called conjunctivitis.  It can be one eye or both eyes. When any of these syndromes occur in cats, veterinarians can identify the cause in less than half of the cases.

Until recently, veterinarians assumed that many of the cases of uveitis were due to toxoplasmosis. Cats are the natural hosts of the toxoplasmosis organism and many free roaming cats have a history of exposure to toxoplasmosis due to consuming infected rodents and birds. We made that assumption based on antibody levels against toxoplasma in the cat’s blood. However the presence of antibody against toxoplasma does not necessarily mean that your cat’s eye problem is related to its toxoplasmosis exposure. The vast majority of cats that are exposed to toxoplasma never develop eye problems. Veterinarians now believe that some of those cases were probably due to bartonella. In one study of cats showing various forms of eye inflammation, 67.5% were positive for bartonella based on blood culture, blood PCR test, or blood serology. Again, results are highly dependent on the lifestyle of the group of cats you sample. 

Is There A Treatment?


Studies have shown that several antibiotics are successful in eliminating bartonella infections. Azithromycin (Zithromax®) is effective. Currently azithromycin is probably the veterinary drug of choice because it also kills mycoplasma which are another common cause of eye inflammation in cats.

The least expensive, and also one of the most effective antibiotic effective against bartonella is doxycycline. When giving doxycycline capsules or tablets your cat, it is very important that you immediately wash the pills down the cat’s throat with pleasant tasting liquids or soup to prevent ulceration and inflammation of their esophagus. These capsules and tablets have a reputation for get stuck in the cat’s esophagus causing damage. You can also have the drug compounded in pleasantly flavored liquid form. 

Rifampicin, (Rifampin® etc.), an antibiotic often used to treat human tuberculosis. It is also effective in treating bartonella when it affects the eyes of humans. It is usually administered in combination with other antibiotics. I have no experience giving it to cats. 

While your cat is being treated, corticosteroid and/or atropine-containing eye drops are often given to inhibit scaring and pathological changes to the structures of your cat’s eye. Non-medicated eye drops also help correct the dry eye which occasionally occurs when azithromycin antibiotic is given. When the treatment is successful, your cat’s blood antibody levels to bartonella should begin to decrease in about 3-5 month. PCR tests for the organism’s presence should decrease even sooner.

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