Cat scratch disease is a bacterial infection that typically causes swelling of the lymph nodes. It usually results from the scratch, lick, or bite of a cat — more than 90% of people with the illness have had some kind of contact with cats, often with kittens.
Bartonella henselae is the bacterium that causes cat scratch disease, and it's found in all parts of the world. Cat scratch disease occurs more often in the fall and winter. In the United States, about 22,000 cases are diagnosed annually, most of them in people under the age of 21. This may be because children are more likely to play with cats and be bitten or scratched.
Fleas spread the bacteria between cats, although currently there is no evidence that fleas can transmit the disease to humans. Once a cat is infected, the bacteria live in the animal's saliva. Bartonella henselae does not make a cat sick, and 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, and cats less than 1 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, then 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 may become warm and red, and occasionally the lymph nodes drain pus.
In most children and adolescents, swollen lymph nodes are the main symptom of the disease, and the illness often is mild. About one third of people with cat scratch disease have other general symptoms. These include fever (usually less than 101° Fahrenheit or 38.3° Celsius), fatigue, loss of appetite, headache, rash, sore throat, and an overall ill feeling.
Atypical cases of cat scratch disease do occur, but they are much less common. In such cases, a person may have infections of the liver, spleen, bones, joints, or lungs, or a lingering high fever without any other symptoms. Some people get an eye infection known as 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.
Contagiousness
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 broken skin or an eye. Sometimes multiple cases of the illness occur in the same family, but these likely result from contact with the same infected animal.
Having one episode of cat scratch disease usually makes people immune for the rest of their lives.
Prevention
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 go a long way toward limiting your child's chances of contracting the disease.
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 in your family has caught cat scratch disease from your family pet, you don't need to worry that the animal will have to be put to sleep. Talk with your veterinarian about the problem.
Incubation
It typically takes 3 to 10 days for a blister or small bump to appear at the site of a scratch or bite. Lymph node swelling usually begins about 1 to 4 weeks later.
Duration
The inoculation lesion where the bacteria entered the body usually takes days to heal. The swollen lymph nodes typically disappear within 2 to 4 months, although they occasionally last much longer.
Professional Treatment
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, a 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:
- skin tests, 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 at all. 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 can be used to treat the disease. If your doctor has prescribed antibiotics, give the medication to your child on schedule for as many days as the doctor has advised.
Home Treatment
A child who has cat scratch disease does not need to be isolated from other family members. Bed rest is not necessary, but it may help if your child tires easily. If your child feels like playing, encourage quiet play while being careful to avoid injuring swollen lymph nodes. To ease the soreness of these nodes, try warm, moist compresses or give your child nonprescription medicines like acetaminophen or ibuprofen.
When to Call the Doctor
Call your doctor whenever your child has swollen or painful lymph nodes in any area of the body, or if your child is ever bitten by an animal. You should call if your child has been bitten or scratched by a cat and the wound does not seem to be healing, an area of redness around the wound keeps expanding for several days, or your 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, has lots of pain in a lymph node, seems very sick, or develops any new symptoms.