Cat scratch disease is an illness that affects people, cats, dogs, and other wildlife. This syndrome was first identified in the 1950’s. People often experience fever, low energy, skin papules, and lymph node enlargement with the potential for much more advanced illness. In the United States the incidence is about 9.3 cases per 100,000 people annually-Jackson et all 1993. It is transmitted to humans from infected cat scratches and bites. A causative agent, Rochalimaea henselae was not identified until 1992; and the following year it was reclassified as Bartonella henselae a gram-negative bacteria. Since then, additional types of Bartonella that cause infections in people have also been identified.
Not every cat scratch or bite is a problem. The wounds must become infected by debris from fleas in order for Cat Scratch Disease to be spread. Any open wound or sore can become infected if a person is in contact with excrement from infected fleas. Children, the elderly, or anyone with a weaker immune system are more susceptible.
The Bartonella bacterium has been identified in cats almost worldwide (multiple countries within Europe, Asia, New Zealand, and the Americas). Bartonella is present in both symptomatic and non-symptomatic felines, with anywhere from 20-40% of healthy cats being carriers. The prevalence is much higher in areas that are warm and humid because these environments are conducive to flea proliferation.
Kittens and flea-infested cats are more likely to carry the bacteria. Felines are more likely to be exposed to Bartonella if they live in multi-cat households, they spend time outside, and/or there is poor flea control. Cats become infected from fleabites or consuming flea debris. Ticks can be carriers; but it is uncertain if they spread illness to cats as well.
Cats themselves can become mildly to quite ill, and multiple systems can be affected. Unexplained fevers are common, with or without enlarged lymph nodes. At the mouth there can be gum inflammation and ulceration. Bartonella can cause congestion and inflammation of the respiratory tract, as well as inflammation and potential ulceration of the eyes. It can also affect the intestinal tract triggering digestive upset with vomiting and diarrhea. Skin and heart maladies are also possible.
It is very difficult to identify Bartonella as the cause of disease, even in cats with significant symptoms. Many different types of tests exist; but no one test is definitive. According to Michael Lappin, a feline infectious disease veterinarian at The UC Davis School of Veterinary Medicine, running a culture of blood or tissues is the gold standard technique for proving infection. It is very challenging however to run this test due to very specialized laboratory requirements, and it takes a very long time to get results. A PCR assay test, which is used to amplify DNA from blood, fluid or other tissue is much faster. But identifying the DNA from Bartonella doesn’t prove that the cat was clinically ill from the infection. Serological testing looks for antibodies to Bartonella using immunofluroescent antibody assay (IFA), enzyme linked immunosorbent assay (Elisa), or Western Blot immunoassay. Positive results here only prove exposure at some time, but not necessarily current infection. False positive and false negative test results can occur, and an ill cat cannot be differentiated from an asymptomatic cat based on antibody testing. It is also no longer thought to be sensitive enough to monitor response to treatment.
Dr. Lappin makes a diagnosis of Bartonella in a cat based on many combined factors. First the cat has symptoms associated with the disease. Other causes have been excluded. There has been a positive test result. And the feline has responded to treatment. There is also great controversy over what treatment to use, and for how long. Generally therapy involves one or more antibiotics for at least 4-6 weeks. Routine testing of asymptomatic cats is not recommended, and routine treatment of asymptomatic felines is not recommended.
The American Association of Feline Practitioners (AAFP) has guidelines to help cat owners protect themselves, with additional care for anyone with a weaker immune system. Flea control should be initiated and maintained year-round. If a family member is immunocompromised, and they want to own a cat, it is best to choose a cat that is over a year and that doesn’t have fleas. Trim cat nails routinely to help prevent Bartonella at the nail tips. Avoid cat scratches and bites. Clean any cat-associated wounds promptly and thoroughly with soap and water. Do not let felines lick any open wounds on a person’s body. Be cautious about adding stray cats or shelter cats to a household without first starting flea control. Keep cats indoors to minimize hunting and exposure to fleas. Treat cat illnesses promptly, and handle any sick cat with extra care to avoid being scratched or bitten. Discuss testing and treatment for Bartonella with your veterinarian.
The main reason I wanted to write this article is to increase awareness about Cat Scratch Fever because it is a concern for people and animals. And to emphasize that fleas do pose a significant health risk to animals and people. There are many illnesses that they can transmit to dogs, cats, and us