Introduction
Cat scratch fever, also known as cat scratch disease (CSD), is an infectious disease that can be transmitted from cats to humans. It is caused by a type of bacteria called Bartonella henselae that cats can carry in their mouths, claws, or fleas.
There are some common myths and misconceptions about cat scratch fever. Many people believe it is just a benign illness or that it cannot cause serious complications. However, while cat scratch fever often resolves on its own, it can sometimes lead to more severe symptoms. There is also a misconception that it is easily transmitted just by a cat scratch when usually a bite or deep puncture wound is required for transmission.
Symptoms
The most common symptoms of cat scratch fever are a rash or swollen lymph nodes near the site of the scratch or bite (Cleveland Clinic). Within 3-10 days of the initial scratch or bite, a red bump will typically form where the cat scratched or bit the person. This bump can then develop into a pustule or blister. As the infection spreads through the lymph nodes, symptoms may include:
- Localized swelling, redness, and pain at the site of the scratch or bite
- Swollen or tender lymph nodes, often in the neck, armpit, or groin
- Fever
- Fatigue
- Headache
- Poor appetite
In rare cases, cat scratch fever can lead to more serious complications like encephalitis, neuroretinitis, arthritis, or damage to the liver or spleen (Johns Hopkins Medicine). However, most people recover fully within a few months.
Causes
Cat scratch fever is caused by a bacterium called Bartonella henselae. This bacteria lives in the bloodstream of cats, especially kittens and stray cats. According to the CDC, up to 30% of cats carry B. henselae in their bloodstream, although most cats with this infection show no symptoms. The bacteria is spread to humans through scratches, bites, or contact with cat saliva.
When a cat harboring B. henselae scratches or bites a person and breaks the skin, the bacteria can enter the wound and infect the person. Cat scratches are the most common cause, but bites and exposure to saliva can also transmit the bacteria. Kittens under the age of 1 are more likely to spread B. henselae than adult cats. Stray cats that live outdoors and hunt rodents are also more likely carriers.
Diagnosis
Cat scratch disease is diagnosed through a combination of patient history, physical examination, blood tests, and medical imaging. Doctors will inquire about any recent scratches, bites, or exposure to cats. The most definitive diagnostic test is a blood test checking for antibodies to Bartonella henselae, the bacteria that causes cat scratch disease.
According to the CDC, there are several types of blood tests that can be used to diagnose cat scratch disease 1:
- Enzyme immunoassay (EIA) to look for antibodies to B. henselae.
- Indirect fluorescent antibody (IFA) staining to detect antibodies.
- Polymerase chain reaction (PCR) and culture to identify the bacteria.
These laboratory tests can confirm the diagnosis within a few days if antibodies or bacterial DNA is detected. Doctors may also order imaging tests like CT scans or ultrasounds to look for enlarged lymph nodes or other abnormalities.
Treatment
Cat scratch fever is typically self-limited and resolves without treatment. Antibiotics are sometimes used in severe cases of cat scratch fever. According to the Cleveland Clinic, the antibiotic azithromycin may be prescribed to try to get rid of the Bartonella bacteria that causes cat scratch fever. However, WebMD notes that most healthy people recover from cat scratch fever on their own within a few weeks or months.
According to a study published in American Family Physician, if an antibiotic is chosen to treat cat scratch disease, azithromycin appears to be effective at reducing the duration of symptoms. However, antibiotics are not routinely recommended and are typically reserved for patients with severe, prolonged symptoms or serious complications.
In most cases, cat scratch fever resolves on its own without medication as the immune system fights off the infection. Treatment focuses on relieving symptoms with measures such as getting rest, staying hydrated, and taking over-the-counter medication like ibuprofen or naproxen for pain and inflammation.
Prevention
There are several ways to help prevent cat scratch disease and avoid getting infected:
Avoid rough play with cats. Cats have sharp claws and teeth that can easily break skin. Play gently and use toys when interacting with cats to reduce scratches and bites. Supervise young children around cats.
Clean wounds right away. If you do get a cat scratch or bite, wash the area immediately with soap and warm water. Use an antiseptic and apply antibiotic ointment if needed. Cleaning wounds helps remove bacteria and prevents infection.
Consider not having a cat if immunocompromised. People with weakened immune systems, such as those with HIV/AIDS, cancer patients undergoing chemotherapy, or organ transplant recipients, are at higher risk for developing complications from cat scratch disease. They should take extra precautions or consider not having a cat.
According to the CDC, other ways to help prevent cat scratch disease include keeping cats indoors and getting cats routinely tested and vaccinated for diseases they can transmit to humans.
Who is at risk?
Anyone exposed to cat scratches or bites can potentially develop cat scratch fever, also known as cat scratch disease (CSD). However, some groups are at higher risk than others. According to the CDC, CSD is most common in children under the age of 15, with around two-thirds of infections occurring in this age group. Younger children tend to play with kittens more often and may receive more scratches or bites as a result. Those with weakened immune systems, such as people with HIV/AIDS, cancer patients undergoing chemotherapy, or organ transplant recipients on immunosuppressant medications, are also at increased risk for CSD. Their weakened immune systems make it harder to fight off the Bartonella henselae bacteria that cause cat scratch fever.
According to the Cleveland Clinic, around 90% of CSD cases are the direct result of a cat scratch or bite. Exposure can also occur if a person has an open cut or wound that comes into contact with areas where a cat lives. Cat fleas can carry the bacteria, so flea bites represent another possible route of transmission.
Overall, CSD is quite common. The CDC estimates around 12,000 hospitalizations and 500 deaths attributed to CSD infections occur in the United States each year. So while cat scratches or bites are usually harmless, it’s important to monitor for any signs of infection, especially for higher risk groups like children and immunocompromised individuals.
Sources:
https://www.cdc.gov/bartonella/bartonella-henselae/faq.html
https://my.clevelandclinic.org/health/diseases/23537-cat-scratch-fever
Complications
While cat scratch fever rarely leads to serious illness, there are some potential complications to be aware of. These include encephalitis, neuroretinitis, and osteomyelitis (Mount Sinai).
Encephalitis is an inflammation of the brain that can occur in approximately 2% of cat scratch fever cases. Neuroretinitis involves inflammation of the optic nerve and retina. Osteomyelitis is an infection of the bone. While concerning, these complications are quite rare. Most people who contract cat scratch fever make a full recovery within a few weeks or months without complications.
Overall, cat scratch fever is generally a mild illness. With proper treatment, serious complications are unlikely. However, it’s important to monitor symptoms and follow up with a doctor if the condition persists or worsens. Prompt treatment can help prevent rare complications from developing.
Myths vs Facts
There are some common myths surrounding cat scratch fever. Here are some myths compared with the facts:
Myth: Cat scratch fever is a made up illness
Fact: Cat scratch fever, also known as cat scratch disease (CSD), is a real diagnosed condition caused by the Bartonella henselae bacteria. It was first described in medical literature in 1950. While rare, it causes symptoms like fever, headache, fatigue, and swollen lymph nodes in people infected by cat scratches, bites, or exposure to fleas from an infected cat.1
Myth: Cats must be gotten rid of if they scratch or bite
Fact: Unless the cat is clearly ill, it is usually safe to keep a cat that has scratched or bitten someone. Proper care of scratch wounds and avoiding contact with an infected cat while ill can prevent transmission. Cats can be treated for fleas and monitored for signs of infection to reduce risk. Removing a well-loved pet may be an extreme measure in most cases of CSD.
Conclusion
In summary, cat scratch fever, also known as cat scratch disease, is a real but rare bacterial illness that can occur after a cat scratch or bite. The infection is caused by the bacteria Bartonella henselae, which cats can carry in their mouths and under their claws.
While the name may sound alarming, cat scratch fever is generally a mild, self-limiting illness marked by fever, headache, fatigue, and swollen lymph nodes near the scratch or bite. Serious complications are very uncommon. Most people recover within 2-4 weeks without treatment.
To help prevent cat scratch disease, proper cat handling and care are important. Gentle play, avoiding scratches, and keeping cats indoors can reduce the risk of transmission. Cats should also be routinely checked by a vet and have their nails trimmed. If a scratch or bite does occur, promptly washing the wound with soap and water is recommended.
So while cat scratch fever is a real condition, it is not a common or serious threat for most cat owners. With proper precautions and care, people can enjoy their feline companions without excess concern over this disease.
