Healthy Living

What Is Cat Scratch Fever?


Cat scratch fever or cat scratch disease is a bacterial infection spread by cats. You can get the cat scratch fever from a scratch or bite of a cat that is infected with the bacterium called Bartonella henselae. Aside from the infected cat’s scratch, you can also acquire the infection if the cat’s saliva comes into contact with an open wound or your sclera (the white of the eye).

After approximately 14 days from the cat’s scratch or bite, a mild infection usually occurs at the site of the scratch or bite. The bitten or scratched area may become swollen with raised lesions and pus. This site is infected and is painful and warm to touch. An individual infected with the cat scratch disease may also develop fever, weakness, headaches, or loss of appetite. Later on, the individual’s lymph nodes, which are nearest to the site of bite or scratch usually become painful or swollen. 

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Make sure to properly wash cat scratches or bites using soap and water. Moreover, do not let your cat lick your wound. Seek immediate medical help if you experience symptoms of infection.

How does the infection occur?

Cats are infected with B. henselae from flea bites or droppings that get into their wounds. Cats usually pick up infected flea droppings between their teeth and under their claws. They get it through scratching or biting infected fleas. They can also get infected after fighting with other infected cats.

The infection spreads to humans when cats infected with B. henselae scratch or bite individuals deep enough to pierce their skin. Infected cats can also transmit the infection when they lick at open wounds of people. 


Cat scratch fever is caused by Bartonella henselae. At some point in time, approximately 40 percent of cats are carriers of the bacterium. However, most carrier cats do not display any signs or symptoms of the disease. Kittens are more prone to having the infection and to spread it to people. Kittens and young cats are also more likely to scratch or bite while they are playing and learning how to attack their prey. 

Although most cats do not display symptoms even if they are infected, severe cases can cause breathing difficulties and infections in their eyes, mouth, or bladder. Children are more prone to becoming infected with cat scratch fever than adults. 


Below are the symptoms that people may experience when they become infected with cat scratch fever:

1. Feline Symptoms

  • In most cases, cats do not show any clinical symptoms
  • A history of flea or tick infestation
  • Swollen glands
  • Fever
  • Loss of appetite
  • Lethargy
  • Reproductive difficulty in some cats

2. Human Symptoms

Most patients infected with cat scratch fever are younger than 21 years old. The following symptoms may be observed in humans:

  • Low-grade fever
  • Chills
  • General ill feeling
  • Fatigue or tiredness
  • Small red blisters or papule at the affected site
  • Swollen appearance of the affected skin area
  • Swollen lymph nodes at the closest site of scratch or bite 
  • Loss of appetite
  • Nausea
  • Myalgia or muscle pain
  • Abdominal cramps

One of the lesser known symptoms is weight loss due to loss of appetite or a sore throat.


For humans infected with cat scratch fever, specific testing might be required to identify as well as isolate the causative agent (B. henselae). Since most cats are asymptomatic, a diagnostic workup is not usually required.

However, in severe infections, a veterinarian will collect a blood sample from the cat for further examination. Most of the time, urinalysis, blood tests, and biochemistry panels are normal.

More specific tests are performed to confirm the diagnosis of cat scratch fever:

  • Blood Culture - The most reliable diagnostic test for cat scratch fever is culturing or growing the causative bacterium from a patient’s blood sample.  
  • Polymerase Chain Reaction (PCR) - This is a more advanced test when it comes to identifying bacterial DNA. It involves taking a tissue sample from the wound or lesions.  
  • Enzyme Immunoassay (EIA) - This test can be used to check your cat’s specific immune response to B. henselae. However, if antibodies are present, it does not necessarily mean that your cat is currently infected with the disease. It may signify that your cat became a carrier of the infection at some point in its life.

However, these tests may not always confirm a B. henselae infection since the bacterium is not always circulating in the bloodstream. Many other tests might be needed to confirm the presence of B. henselae.

Risk Factors

Immunosuppressed individuals such as patients undergoing chemotherapy and people with AIDS have an increased risk of having more severe symptoms of the disease. It is highly recommended for cat owners to get their cats tested for B. henselae.

When getting a cat, make sure that it gets tested before bringing it home and that the cat comes from a flea-free environment.


If cat scratch fever is not accurately diagnosed and promptly treated, then certain complications may arise, which include:

  • Neuroretinitis: It is basically an inflammation of the optic nerve as well as the retina in the eye that leads to blurry vision. The inflammation is known to occur when the bacterium responsible for cat scratch fever reaches the eye and causes a temporary impaired vision. An individual's vision would return back to normal once the infection goes away.
  • Encephalopathy: When the causative agent of cat scratch fever spreads to the brain, encephalopathy or brain disease can occur. Some encephalopathy cases may lead to permanent damage to the brain or death. 
  • Osteomyelitis: It is a bone infection resulting from an injury, surgery, or infection that may lead to bone damage. In certain cases, the damage caused to the bone becomes so severe that the doctor would suggest an amputation of the part that has been completely damaged.
  • Parinaud Oculoglandular Syndrome: It is an infection of the eye that has symptoms quite similar to pink eye. Cat scratch fever is known to be one of the most common causes of this particular syndrome. This syndrome can be due to a Bartonella infection that reaches the eye through the bloodstream. This particular syndrome is known to mostly respond well to antibiotic treatment. However, in certain rare cases, surgery would be required to remove the infected tissues of the eye.


Most cases of cat scratch fever are not life-threatening, except for immunosuppressed individuals. In certain cases, the doctor can prescribe an antibiotic when there is a severe infection and in people who have an impaired immune system due to certain medical conditions such as HIV/AIDS, lupus, or arthritis.


You can prevent cat scratch fever by avoiding direct contact with cats. If you already have a cat, try not to roughly play with it to avoid being scratched or bitten. Ensure to wash your hands thoroughly after playing or touching a cat to help prevent the disease. Also, make sure to keep your pet cat indoors and give anti-flea medications to reduce the risk of your cat to contract the bacterium.

  • Be careful when touching a stray cat: Since stray cats spend most of their time outdoors and in various locations, they have a greater chance of coming into contact with infected fleas.
  • Take care of your cat:  If you have cats at home, then it is essential to trim their nails on a regular basis and use certain products that would keep fleas at bay. Consult a vet to know which products should be used since not all over-the-counter products are safe for use.
  • If you have health problems, choose an older cat to adopt: If you want to adopt a cat but have certain health problems such as an impaired immune system, you can choose an older cat since young kittens are more prone to having cat scratch disease.
  • Maintain proper hygiene: Wash your hands properly with mild soap and water after playing with a cat. If you have been bitten or scratched by a cat, then thoroughly wash the site of bite or scratch with mild soap and water. The same would also apply when a cat licks any of your open wound or scab to avoid the spread of infection.


There is no known vaccine when it comes to the prevention of cat scratch fever. However, you can avoid the disease through effective flea control and preventive measures. Seek immediate medical help if you develop any symptoms of cat scratch fever.