Cat scratch fever–also called cat scratch disease, or CSD–is a bacterial infection. The disease gets its name because people contract it from cats that are infected with Bartonella henselae bacteria, one of the most common bacteria in the world. According to the Michigan Department of Agriculture & Rural Development, about 24,000 people get cat scratch fever in the United States each year.
You can get cat scratch fever from being bitten or scratched by an infected cat. You can also get the disease if saliva from an infected cat gets into an open wound on your body or touches the whites of your eyes.
Cats can carry Bartonella, but they do not generally get sick from the bacteria, so you cannot always tell if they are carriers. It is believed that cats contract Bartonella henselae from infected fleas, but there is no evidence that humans can contract the bacteria directly from fleas. Up to 40 percent of cats carry the bacteria at some time in their lives, most commonly when they are kittens. Your veterinarian can test your cat to see if it is carrying the bacteria, but cats tend to carry the bacteria only for a short time and treatment is usually not recommended.
Common symptoms of cat scratch fever include:
- a bump or blister where you were bitten or scratched
- swollen lymph nodes near where you were bitten or scratched
- a low-grade fever
Less common symptoms of cat scratch fever include:
- loss of appetite
- weight loss
- sore throat
Anyone who owns a cat or interacts with a cat is at risk for contracting cat scratch fever. You have an increased risk of becoming seriously ill from cat scratch fever if you have a weakened immune system.
If your doctor believes you may have cat scratch fever, he or she will perform a physical examination to see if your spleen (an organ above your stomach) is enlarged. Cat scratch fever is difficult to diagnose by the symptoms alone. An accurate diagnosis can be made by performing a Bartonella henselae IFA blood test to see if the bacteria are present in your body.
Cat scratch fever is usually not serious and generally does not require treatment. Antibiotics are used to treat serious cases of cat scratch fever and to treat people who have weakened immune systems from conditions such as HIV/AIDS.
Most people get better without treatment, and those who do need treatment generally get better with antibiotics. In some cases, people develop serious complications from the bacteria. These complications are more likely to occur in people who have compromised immune systems.
Possible complications from cat scratch fever include:
Encephalopathy is a brain disease that can occur when the bacteria responsible for cat scratch fever spread to the brain. In some cases, encephalopathy results in permanent brain damage or death.
Neuroretinitis is an inflammation of the optic nerve and retina in the eye that causes blurred vision. The inflammation can occur when the bacteria responsible for cat scratch fever travels to the eye, causing impaired vision. Vision usually returns to normal after the infection is gone.
Osteomyelitis is a bacterial infection in the bones, which can result in bone damage. In some cases, the bone damage is so severe that amputation is necessary.
Parinaud’s syndrome is an eye infection that produces symptoms similar to pink eye. Cat scratch fever is one of the most common causes of the syndrome. Parinaud’s syndrome can be caused by Bartonella henselae entering the eye directly, or by the bacteria traveling through the bloodstream to the eye. The syndrome usually responds well to antibiotic treatment. In rare cases, surgery is needed to remove infected tissues from the eye.
You can prevent cat scratch fever by avoiding contact with cats. If you have a cat, you can reduce your risk of getting cat scratch fever by avoiding rough play that could lead to you being scratched or bitten. Washing your hands after playing with your cat may also help prevent the disease. Keep your cat indoors and administer anti-flea medication to reduce the risk of your cat contracting Bartonella henselae.