Introduction
Cats frequently use their claws and teeth to play or defend themselves. While most cat scratches are harmless, there is a small risk of developing an infection or illness from a cat scratch. One potential illness is called cat scratch disease (CSD), which is caused by a bacterial infection. CSD can occur when a person is scratched, bitten, or licked by a cat carrying the bacteria Bartonella henselae. Most people experience mild symptoms and recover on their own, but CSD can become serious in immunocompromised individuals. Beyond CSD, other potential concerns from a cat scratch include bacterial infections of the skin and soft tissue. However, the risk of illness remains relatively low, and healthy individuals usually heal from a routine cat scratch with proper first aid and wound care.
What is Cat Scratch Disease?
Cat scratch disease is caused by a type of bacteria called Bartonella henselae. This bacteria is typically found in the saliva of kittens and cats. Cat scratch disease occurs when the bacteria enters the human body, usually through a scratch, bite, or cut from a cat (“Cat Scratch Disease: Symptoms, Causes, and Treatment,” 2022).
The disease is transmitted when the claws or teeth of a cat break the skin. It can also be spread if saliva from a cat’s mouth, nose, or eyes contacts broken skin or mucous membranes on a human. Bartonella henselae bacteria enter the skin through these cuts or scratches and infect the body (YouTube, n.d.).
Most cases of cat scratch disease occur in children under the age of 12. Young children are at higher risk because they are more likely to play rough with cats and suffer bites or scratches. They also may lack good hygiene practices that can prevent infection after interacting with cats (“Cat Scratch Disease: Symptoms, Causes, and Treatment,” 2022).
Common Symptoms
The most common symptoms of cat scratch disease include:[1]
- A red bump at the scratch site. This usually appears 3-10 days after the scratch and can last a few weeks. The bump may drain pus.
- Fever, which may come and go. Fevers from cat scratch disease are usually mild.
- Swollen lymph nodes near the scratch. This is usually the first sign and occurs 1-3 weeks after the scratch. The lymph nodes may become tender and swollen.
- Fatigue. Many people with cat scratch disease feel tired or worn down.
Other less common symptoms include headache, poor appetite, and weight loss. In rare cases, more severe complications can occur if the infection spreads to other areas like the eyes, liver, or spleen.
Diagnosis and Testing
Cat scratch disease is primarily diagnosed based on the patient’s symptoms and exposure history. However, the following tests may help confirm the diagnosis:
The doctor will likely perform a physical exam of the lymph nodes near the scratch or bite to feel for swelling or tenderness. Lymph nodes that are infected often become swollen and painful.
The doctor may order a blood test to look for antibodies to Bartonella henselae. According to the University of Rochester Medical Center, finding these antibodies is a reliable way to diagnose cat scratch disease, but it may take some time for antibody levels to rise high enough to be detected.
If antibody levels are unclear, the doctor may recommend getting a biopsy of the swollen lymph node. A small sample can be analyzed to look for evidence of bacterial infection. According to a 2019 study, polymerase chain reaction (PCR) analysis of the lymph node sample can also be used to detect the presence of Bartonella henselae DNA.
Specialized antibody testing like the Bartonella henselae IFA IgG/IgM test from ARUP Laboratories may also assist in diagnosis by distinguishing between IgM antibodies (indicating a recent infection) and IgG antibodies (indicating past exposure).
Treatment
Most cases of cat scratch disease will resolve on their own without the need for treatment. According to the Centers for Disease Control and Prevention (CDC), symptoms usually go away in 2-4 months even without antibiotics. However, treatment may be recommended in severe cases or if the infection spreads to other parts of the body.
For severe cat scratch disease, antibiotics may be prescribed to fight the bacterial infection. Commonly prescribed antibiotics include azithromycin, ciprofloxacin, rifampin, gentamicin, and trimethoprim-sulfamethoxazole. Taking antibiotics can help shorten the duration of symptoms from about 3 months to as little as 2-3 weeks (Eleftheriotis, 2022).
In rare cases, the lymph nodes may become very swollen and painful due to the infection. If antibiotics are not effective at reducing the swelling, surgical removal of the affected lymph nodes may be necessary. This is usually only required in about 1% of cat scratch disease cases (My Pet and I).
Prevention
There are a few key ways to help prevent cat scratch disease in humans:
Keep cats indoors and free of fleas. Fleas are a common carrier of the Bartonella bacteria that causes cat scratch disease. Keeping cats indoors reduces their exposure to fleas, and regularly using flea control medication can eliminate fleas on indoor cats. For more on flea prevention, see this article.
Wash hands after handling cats. Thoroughly washing hands with soap and water after petting cats, cleaning the litter box, or being scratched or bitten can remove any Bartonella bacteria and prevent transmission. Scrub hands for at least 20 seconds.
Clean and disinfect cat scratches. Immediately washing cat scratches or bites with soap and water can help flush out bacteria. Be sure to disinfect the wound afterwards with an antiseptic. Keeping the wound clean while it heals can prevent infection.
Other Potential Illnesses
While cat scratch disease is the most common illness that can result from a cat scratch, there are some other potential illnesses to be aware of:
Rabies is a viral infection that affects the central nervous system of mammals, including cats. Rabies is transmitted through saliva, so if an infected cat scratches or bites a human, rabies can potentially be transmitted. However, rabies is relatively rare in domestic cats that live indoors. Symptoms include fever, headaches, anxiety, confusion, and hydrophobia. Rabies has a very high fatality rate if left untreated. https://www.cdc.gov/rabies/exposure/animals/cats.html
Cat scratch fever, also known as cat scratch disease, is caused by the Bartonella henselae bacteria. Symptoms include swollen lymph nodes, fever, headaches, and fatigue. It can be identified through blood tests and lymph node biopsies. Cat scratch fever usually resolves on its own, but antibiotics are sometimes prescribed for severe cases. https://www.cdc.gov/bartonella/bartonella-henselae/faq.html
Ringworm is a fungal skin infection that cats can transmit through scratches. It causes ring-shaped rashes on the skin that can be very itchy. Ringworm is treated with topical antifungal medications. https://www.cdc.gov/healthypets/diseases/ringworm.html
Pasteurellosis is a bacterial infection caused by Pasteurella multocida bacteria that cats may harbor in their mouths. If a cat bite or deep scratch breaks the skin, it can cause swelling, pain, and redness at the wound site. Pasteurellosis is treated with antibiotics. Severe infections may require hospitalization. https://www.cdc.gov/pasteurella/healthcare/infections.html
When to See a Doctor
If you develop concerning symptoms from a cat scratch, it’s important to see your doctor. Contact your doctor right away if you experience any of the following:
- Fever lasting over a week (1)
- Severe swelling at the scratch site
- Respiratory symptoms like cough or difficulty breathing
A fever lasting more than a week could indicate an infection that your body is having trouble fighting off on its own. Significant swelling around the scratch can also suggest an infection or abscess that needs medical treatment (2). Respiratory symptoms may arise if the infection spreads to the lungs.
Seeing your doctor promptly if any of these concerning symptoms develop allows for earlier diagnosis and treatment if needed. Your doctor can run tests to check for cat scratch disease or other infections and provide appropriate care. With treatment, you’re more likely to recover fully and avoid complications.
- https://medium.com/illumination/cat-scratch-disease-1d2cb24093ad
- https://biosidmartin.com/what-is-the-life-cycle-of-bartonella/
Conclusion
In summary, while most cat scratches do not lead to illness, it is still important to monitor for any concerning symptoms following a cat scratch. Cat scratch disease, caused by the bacteria Bartonella henselae, can occur in a small percentage of cat scratches. Symptoms usually appear 3-10 days after the scratch and include swollen lymph nodes near the scratch site, fever, headache, fatigue, and loss of appetite. In rare cases, more severe symptoms can develop. Diagnosis involves looking at symptoms and medical history, and may include blood tests, cultures, or biopsy of lymph nodes. Treatment involves antibiotics for severe cases. Most mild cases resolve on their own within a few months. To help prevent cat scratch disease, promptly clean any cat scratches with soap and water, trim cats’ nails, and avoid rough play. Seek medical attention for any severe symptoms or lymph node swelling after a scratch. While the vast majority of cat scratches do not lead to illness, it is wise to be aware of potential symptoms so proper treatment can be obtained if needed.
References
The Cats Protection (Advocacy Group), The Humane Society (Non-Profit Organization), The American Veterinary Medical Association (Professional Association), The Centers for Disease Control and Prevention (Government Agency), WebMD (Medical Reference Site)