Cat Scratch Disease

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About Cat Scratch Disease

Cat scratch disease, a bacterial infection that causes swelling of the lymph nodes, usually is due to the scratch, lick, or bite of a cat — more than 90% of people who contract it had contact with cats or kittens.

Bartonella henselae, the bacterium that causes this disease, is found in all parts of the world. In the United States, about 22,000 cases are diagnosed annually, more often in the fall and winter and usually in kids, probably because they're more likely to play with cats and be bitten or scratched.

Fleas spread the bacteria between cats, although there's no evidence that fleas can transmit the disease to humans. The bacteria live in infected cats' saliva but don't make the animals sick; in fact, kittens or cats may carry the bacteria for months.

Experts believe that almost half of all cats have a Bartonella henselae infection at some time in their lives, with those younger than a year old are more likely to be infected.

Signs and Symptoms

Most people with cat scratch disease remember being around a cat, but often cannot recall receiving a scratch or a bite. A blister or a small bump develops several days after the scratch or bite and may be mistaken for a bug bite. This blister or bump is called an inoculation lesion (a wound at the site where the bacteria enter the body), and it is most commonly found on the arms and hands, head, or scalp. These lesions are generally not painful.

Usually within a couple of weeks of a scratch or bite, one or more lymph nodes close to the area of the inoculation lesion will swell and become tender. (Lymph nodes are round or oval-shaped organs of the immune system that are often called glands.) For example, if the inoculation lesion is on the arm, the lymph nodes in the elbow or armpit will swell.

These swollen lymph nodes appear most often in the underarm or neck areas, although if the inoculation lesion is on the leg, the nodes in the groin will be affected. They range in size from about ½ inch to 2 inches in diameter and may be surrounded by a larger area of swelling under the skin. The skin over these swollen lymph nodes can become warm and red, and occasionally the lymph nodes drain pus.

In most kids, swollen lymph nodes are the main symptom of the disease and the illness often is mild. If people have other general symptoms, they might include fever (usually less than 101ºF or 38.3ºC ), fatigue, loss of appetite, headache, rash, sore throat, and an overall ill feeling.

Atypical cases do occur, but are not common. In such cases, someone might have infections of the liver, spleen, bones, joints, or lungs, or a lingering high fever without other symptoms. Some get an eye infection (Parinaud oculoglandular syndrome), with symptoms including a small sore on the conjunctiva (the membrane lining the eye or inner eyelid), redness of the eye, and swollen lymph nodes in front of the ear. Others may develop inflammation of the brain or seizures, although this is rare. All of these complications of cat scratch disease usually resolve without any lasting illness.


Cat scratch disease is not contagious from person to person. The bacteria are spread by the scratch or bite of an infected animal, most often a kitten. They can also be transmitted if the animal's saliva comes in contact with an eye or through broken skin. Sometimes multiple cases occur in the same family, usually via contact with the same infected animal.

Having one episode of cat scratch disease usually makes people immune for the rest of their lives.


If you're concerned about cat scratch disease, you do not need to get rid of the family pet. The illness is relatively rare and usually mild, and a few steps can help limit your kids' chances of contracting it.

Teaching kids to avoid stray or unfamiliar cats can reduce their exposure to sources of the bacteria. To lower the risk of getting the disease from a family pet or familiar cat, kids should avoid rough play with any pets so they can avoid being scratched or bitten. Have your family members wash their hands after handling or playing with a cat.

If your child is scratched by a pet, wash the injured area thoroughly with soap and water. Keeping the house and your pet free of fleas will reduce the risk that your cat could become infected with the bacteria in the first place.

If you suspect that someone caught cat scratch disease from your family pet, don't worry that your cat will have to be euthanized (put to sleep). Talk with your veterinarian about how to handle the problem.

Incubation and Duration

It usually takes 3 to 10 days for a blister or small bump to appear at the site of a scratch or bite. Lymph node swelling begins about 1 to 4 weeks later.

The inoculation lesion where the bacteria entered the body usually takes 1-3 weeks to heal. The swollen lymph nodes disappear within 2 to 4 months, although occasionally last much longer.


Doctors usually diagnose cat scratch disease based on a child's history of exposure to a cat or kitten and a physical examination. During the exam, the doctor will look for signs of a cat scratch or bite and swollen lymph nodes. In some cases, doctors use laboratory tests to help make the diagnosis, including:

  • blood tests and cultures to rule out other causes of swollen lymph nodes
  • a blood test that is positive for cat scratch disease
  • a microscopic examination of a removed lymph node that shows signs of cat scratch disease

Most cases of cat scratch disease resolve without any treatment. Rarely, a swollen lymph node becomes so large and painful that the doctor may recommend removing fluid from the node with a needle and syringe.

Antibiotics sometimes are used to treat the disease. If your doctor has prescribed antibiotics, give them to your child on schedule and for as many days as prescribed.

Kids with cat scratch disease don't need to be isolated from other family members. Bed rest is not necessary, but can help if a child tires easily. If your child feels like playing, encourage quiet play while being careful to avoid injuring swollen lymph nodes. To ease sore nodes, try warm, moist compresses or give your child nonprescription medicines like acetaminophen or ibuprofen.

When to Call the Doctor

Call the doctor whenever your child has swollen or painful lymph nodes in any area of the body. And always call your doctor if a child is bitten by an animal, especially if:

  • the bite or scratch was from a cat and the wound does not seem to be healing
  • an area of redness around the wound keeps expanding for several days
  • the child develops a fever that lasts for a few days after receiving the scratch or bite

If your child has already been diagnosed with cat scratch disease, call the doctor if your child has a high fever, lots of pain in a lymph node, seems very sick, or develops new symptoms.

Reviewed by: Joel Klein, MD
Date reviewed: July 2012

Related Resources

OrganizationCenters for Disease Control and Prevention (CDC) The CDC (the national public health institute of the United States) promotes health and quality of life by preventing and controlling disease, injury, and disability.

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Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.

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