Cat-Scratch Disease

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What is cat-scratch disease, and how do people get it?

Cat-scratch disease is an infection caused by a type of bacteria (germs) carried in cat saliva. This bacteria is called Bartonella henselae and can be passed from a cat to a human. Doctors and researchers believe that cats may get the bacteria from fleas.

Cat-scratch disease is not a severe illness in people who are healthy. But it can be a problem in people who have weak immune systems. These include people who are receiving chemotherapy for cancer, those who have diabetes or those who have acquired immunodeficiency syndrome (AIDS).

Cat-scratch disease is also called cat-scratch fever.


What are the symptoms of cat-scratch disease?

A sore or blister may develop where a cat has bitten or scratched you. It may take 3 to 10 days for the sore or blister to appear after the bite or scratch. The sore or blister may take a long time to heal.

An infection of the lymph nodes (also called lymph glands) also develops, most often in the glands that are near the place where you got the cat scratch or cat bite. For example, if the infection is from a cat scratch on your arm, the glands in your armpit may become tender and swollen. The lymph nodes may swell to an inch or more in size. You may also run a low-grade fever (up to 102°F).

Should I call my doctor if I am bitten or scratched by a cat?

Call your family doctor if you notice any of the following problems:

  • A cat scratch or bite that does not heal in the usual length of time.
  • An area of redness around a cat scratch or bite that continues to get bigger for more than 2 days after the injury.
  • Fever that lasts for several days after a cat scratch or bite.
  • Painful and swollen lymph nodes for more than 2 or 3 weeks.
  • Bone or joint pain, abdominal pain (without fever, vomiting or diarrhea) or an unusual degree of tiredness for more than 2 or 3 weeks.

Causes & Risk Factors

What causes cat-scratch disease?

You can get cat-scratch disease from a cat bite or scratch. You can get the infection after a cat scratches you if the cat's paws have the bacteria on them. (A cat can get the bacteria on its paws when it licks itself.)

With a cat bite, the cat can pass the bacteria to you in its saliva. You can also get the bacteria in your eyes if you pet a cat that has the bacteria on its fur and then rub your eyes. Many people who get cat-scratch disease do not remember being scratched or bitten by a cat.

Diagnosis & Tests

How is cat-scratch disease diagnosed?

If you remember that you were bitten or scratched by a cat, your doctor will probably be able to diagnose the illness based on the fact that you were bitten or scratched and then developed painful, swollen lymph nodes. When the diagnosis is not clear, a blood test may help your doctor make the diagnosis.


Can cat-scratch disease be prevented?

Avoiding cats is the simplest way to prevent the disease, but it is not usually necessary to get rid of your cat. Try to avoid any situation where you might be bitten or scratched by a cat. Do not tease or provoke a cat. Most scratches and bites come from cats that are provoked. Washing your hands carefully after handling your cat is another way to prevent the infection. Getting rid of fleas on your cat may also keep you and your family members from catching the infection.

Cats only seem to be able to transmit this infection for a few weeks. Young cats seem to be more likely to carry the bacteria than older cats. Households with kittens have higher rates of infection. If the kittens have fleas, the infection rate is even higher.


How is cat-scratch disease treated?

In most people, cat-scratch disease clears up without treatment. Often, taking an over-the-counter pain reliever such as aspirin, ibuprofen (some brands: Motrin, Advil) and naproxen (one brand: Aleve) and applying heat compresses to the affected area can help relieve pain and discomfort.

However, antibiotics (medicines that kill bacteria) may be needed when infected lymph nodes stay painful and swollen for more than 2 to 3 months. Antibiotics may also help if you have a fever for a long time or if the infection is in your bones, liver or another organ.

If a lymph node is very large or painful, your doctor may drain it to help relieve the pain. The lymph node is drained by putting a needle through normal skin off to the side of the node and moving the needle to the swollen node. The needle is then inserted into the node and the fluid in the node is drained out.

Should cats be treated?

Cats typically don't require treatment. The bacteria usually don't cause cats to get sick. They merely carry the bacteria that cause cat-scratch disease in people. If you are worried that your cat may be experiencing symptoms from the Bartonella henselae bacteria, contact your vet.


Questions to Ask Your Doctor

  • What is the right treatment for me?
  • My cat scratched me. Should I call my doctor?
  • Is there any way to know whether my cat carries the Bartonella henselae bacteria?
  • My child has diabetes. Should I get rid of my cat?
  • How should I treat the scratch?