Cat scratch fever, also called cat scratch disease (CSD), is a bacterial infection. The disease gets its name because people contract it from cats infected with Bartonella henselae bacteria, one of the most common bacteria in the world.
You can get cat scratch fever from a bite or scratch from 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.
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.
Cats can carry Bartonella but they don’t generally get sick from the bacteria, so you can’t always tell if they are carriers. It’s believed that cats contract Bartonella henselae from infected fleas, but there’s no evidence that humans can contract the bacteria directly from fleas. According to the Centers for Disease Control and Prevention, 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’s carrying the bacteria, but cats tend to carry the bacteria only for a short time. Treatment isn’t usually recommended.
Common symptoms of cat scratch fever include:
- a bump or blister at the bite or scratch site
- swollen lymph nodes near the bite or scratch site
- a low-grade fever
Less common symptoms of cat scratch fever include:
- loss of appetite
- weight loss
- sore throat
If your doctor believes you may have cat scratch fever, they will perform a physical examination to see if you have an enlarged spleen (an organ above your stomach). Cat scratch fever is difficult to diagnose from the symptoms alone. Doctors can make an accurate diagnosis by performing an indirect fluorescent antibody (IFA) blood test to see if the Bartonella henselae bacteria are present in your body. In this test, antibodies that are labeled with dye will attach to existing antibodies of Bartonella (sometimes called anti-antibodies) and “light up” during the test.
There are a number of possible complications from cat scratch fever.
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 due to 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 necessary to remove infected tissues from the eye.
Cat scratch fever usually isn’t serious and generally doesn’t require treatment. Antibiotics treat serious cases of cat scratch fever and people who have weakened immune systems from conditions such as HIV or AIDS.
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.
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.