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Cat scratch fever can happen when a person receives a bite, scratch, or lick from a cat that is infected with the bacteria Bartonella henselae.

The infection does not usually cause severe complications, but it can lead to problems for people with a weak immune system. Knowing how to spot cat scratch fever can ensure a person receives swift treatment.

Cats can transmit several types of infections to humans. Some of these diseases can be severe. Carrying out routine care for a cat often reduces the risk of many of these diseases.

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A small bump or blister may appear 3–14 days after a scratch.

A person can get cat scratch fever after a scratch or bite from an infected cat. The Bartonella henselae (B. henselae) bacteria live in a cat's saliva. They can pass to a person through an open area of skin.

Cat scratch fever is more common in the fall and winter when people are inside and playing with their cats. Children are more likely than adults to have it, and playing roughly with a cat increases the chances of getting scratched.

Cat scratch fever does not usually cause symptoms in the first few days or weeks after exposure when the bacteria are multiplying in the body.

About 3 to 14 days after the infection first occurred, a person may see a small bump or blister on the contact area, most commonly on the:

  • arms
  • hands
  • scalp
  • head

Doctors call this an inoculation lesion. This lesion may not occur in some cases, or an individual may not notice it on their body.

A few weeks later, the lymph nodes near the lesion may become swollen or tender.

Lymph nodes are responsible for filtering bacteria and other particles and for creating immune system cells. They usually feel like small, spongy, round or oval bumps.

If a person has had a bite or scratch on the arm, the lymph nodes under the arm or near the elbow may be especially tender.

Sometimes, the lymph nodes swell as much as 2 inches across. They may be warm to the touch, fluid-filled, or red. They may remain swollen for 2–3 weeks.

For most people, swollen lymph nodes are the only symptom. However, other symptoms that might occur include:

A person should see a doctor if they have a scratch that continues to get larger after 2 days.

Cat scratch fever does not usually cause severe symptoms, but some people may develop a high temperature that does not improve with time. Some people can also experience infections in the bones, joints, liver, lungs, or spleen.

According to the Centers for Disease Control and Prevention (CDC), the most severe symptoms usually occur in children aged 5 years and under.

Cat scratch fever does not usually need emergency care, but sometimes it does. A person should contact their doctor immediately if they experience the following symptoms:

  • a cat bite or scratch that is not healing or is getting worse
  • the red area around a bite or scratch is enlarging
  • a high fever that lasts more than 2 days after the bite or scratch
  • severe pain

Cat scratch fever can be difficult to diagnose because a number of other conditions have the same symptoms. The physician will ask about the individual's medical history and whether they have had any interactions with a cat.

The doctor will then examine the scratched area and look for any swollen lymph nodes.

This is usually sufficient for a diagnosis, but sometimes they may suggest further tests to make sure the person does not have another condition.

The doctor might take some blood and send it to the lab to find out what kind of bacteria are present. One blood test can test specifically for cat scratch fever.

Most cases of cat scratch fever are mild, and a doctor will not always prescribe treatment. If symptoms are moderate to severe, they may prescribe an antibiotic.

At-home treatments for the condition include bed rest if needed, and an over-the-counter pain reliever if the lymph nodes are painful or especially tender.

Children can mostly continue with their usual activities, but they should avoid hitting or interfering with the affected lymph nodes.

If a person has had cat scratch fever once, they are unlikely to have it again.

Cats can transmit cat scratch fever to people, but people do not usually pass it to each other. If one family member is affected, others should practice caution around a family cat, as the cat could infect them also.

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Regular vacuuming can keep the risk of fleas down.

An episode of cat scratch fever does not mean a family should necessarily get rid of their pet. However, to prevent cat scratch fever, people should:

  • only adopt a cat that is more than 1 year old if a family member has poor immunity, as kittens are most likely to have the disease
  • avoid rough play around a cat or kitten
  • never allow a cat to lick wounds or open areas of skin
  • avoid petting stray or feral cats
  • wash hands and any other affected areas after playing with a cat

Fleas pass the infection from one cat to another.

To prevent a flea infestation:

  • vacuum the home frequently
  • use flea prevention, such as medication, to protect the cat from flea bites
  • contact a pest control company if a lot of fleas appear in a home

The CDC estimate that around 40 percent of cats carry the B. henselae bacteria at some point in their lives. Most of the time, they do not show signs of illness.

Symptoms

Cats get the infection when they scratch and bite at fleas that infect them or fight with cats that are carriers.

If a cat has fleas or visible scratches, a person may wish to practice caution when handling their cat. Once a cat has the cat scratch fever infection, it can carry the bacteria for several months. During this time, it can pass on the infection.

Cats with the bacteria often have no symptoms, but they may have a fever that lasts for 48–72 hours.

In rare cases, cat scratch disease can cause severe symptoms in cats.

These include:

  • fever
  • vomiting
  • low appetite
  • lethargy
  • swollen lymph nodes
  • red eyes
  • inflammation in the mouth

The infection can remain for several months in the cat, and symptoms may reappear at times of stress, for example, after trauma or surgery or alongside another illness.

Diagnosis and treatment

A vet can inspect a cat for fleas and make recommendations about flea prevention and avoiding scratches and bites.

A test is available for the bacteria, but doctors do not usually recommend it for cats that have no symptoms. The bacteria are widespread, and the test can be unreliable.

Cats do not usually need antibiotics unless they have noticeable symptoms.

Prevention in cats

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Children should avoid playing roughly with cats do reduce the risk of getting scratched.

Taking steps to reduce fleas in a cat can reduce the likelihood of cat scratch fever. People can care for their cats by doing the following:

  • applying or administering a vet-approved flea treatment regularly
  • keeping a cat indoors to avoid contact with stray or infected animals
  • keeping a cat's nails trimmed and neat
  • scheduling and maintaining regular checkups with a vet

There is currently no vaccine against cat scratch fever bacteria.

Products to protect a cat from fleas are available for purchase online.

Other conditions cats can spread

Apart from cat scratch fever, a cat can carry other diseases.

These include:

Campylobacteriosis: Bacteria cause an intestinal infection.

Cryptosporidiosis: A parasite causes diarrhea and abdominal cramping.

Plague: Although rare in America, this can occur if a person takes their cat to another country.

Rabies: Cats should have regular vaccinations to prevent rabies infection.

Ringworm: Kittens are especially likely to carry this fungal infection. It causes bald patches on the skin.

Tapeworm: Most common in children, this infection occurs when a person ingests a flea from a cat that has tapeworm larvae.

Toxocara infection: This condition does not always cause symptoms, but it can give rise to severe complications, such as blindness.

Toxoplasmosis: It is crucial to avoid this during pregnancy. Complications include growth and eye problems in the unborn child and pregnancy loss.