Cat Scratch Disease: Causes, Symptoms, Diagnosis, and Prevention
Get detailed insights into cat scratch disease—its causes, symptoms, diagnosis, complications, treatment, and prevention strategies.
Cat Scratch Disease
Cat scratch disease (CSD), also called cat scratch fever, is an infectious illness caused by the bacterium Bartonella henselae. The disease is usually transmitted to humans through the scratch or bite of an infected cat, or through exposure to its saliva or flea-infested fur. While most healthy people recover without complications, cat scratch disease can occasionally lead to more serious problems, especially in children and those with weakened immune systems.
What Is Cat Scratch Disease?
Cat scratch disease is a bacterial infection most commonly spread by cats. The illness typically results in swollen lymph nodes, mild fever, and skin changes at the site of injury. It primarily affects children and young adults, but anyone exposed to infected cats can get the disease.
- Causative agent: Bartonella henselae bacterium
- Primary transmission: Cat bites, scratches, or saliva, especially from kittens
- Other possible transmission: Fleas that carry the bacteria on cats
Causes of Cat Scratch Disease
The root cause of cat scratch disease is infection with Bartonella henselae. This bacterium is most often found in the saliva and on the claws of infected cats. Young cats, particularly kittens under the age of one, are more likely to harbor and transmit the organism due to higher rates of flea infestation and biting or scratching behavior.
- Cats become infected mainly through flea bites.
- Humans are infected when an infected cat scratches, bites, or licks an open wound or broken skin.
- It is possible, though uncommon, to contract the disease by contact with flea-infested cats or their environments.
How Is Cat Scratch Disease Spread?
Most infections occur after a scratch or bite that breaks the skin. The bacteria enter the body and trigger localized or systemic symptoms within one to three weeks. Less commonly, a person may develop the disease when cat saliva (containing the bacteria) comes into contact with open skin, the eyes, nose, or mouth.
- Direct transmission: From a cat’s scratch or bite penetrating the skin.
- Indirect transmission: From contaminated cat saliva contacting mucous membranes or broken skin.
- Flea vector: Flea dirt (feces) carrying the bacteria is groomed into a cat’s fur or claws, which may then infect humans.
Who Is at Risk?
While anyone exposed to infected cats is susceptible to cat scratch disease, certain groups are at increased risk of developing the illness or complications.
- Children younger than 15 years are most commonly affected due to more frequent and rambunctious interaction with cats.
- Immunocompromised individuals, including those with HIV/AIDS, organ transplants, or cancer, are more likely to develop severe or atypical forms.
- People who work with cats (such as veterinarians, animal shelter workers), and households with multiple cats or kittens.
- Households or environments with high rates of flea infestation.
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Symptoms of Cat Scratch Disease
Symptoms of CSD generally develop within 3–14 days after the scratch, bite, or other exposure. The initial manifestation is usually a small, raised bump or blister called a papule or pustule at the site of injury. This is typically followed by regional lymph node swelling (lymphadenopathy) near the affected area.
- Localized skin lesion: Small red bump, sore, or blister at the scratch or bite site.
- Swollen, tender lymph nodes: Most often near the entry site (e.g., armpits, neck, groin).
- Low-grade fever
- Fatigue, malaise, or general discomfort
- Headache
- Loss of appetite (anorexia)
- Body aches, joint pain
- Occasional body rash
Symptoms usually appear 1–3 weeks after the exposure, but in some cases, the delay can be as long as 6 weeks. The disease often resolves without treatment within 2–4 months, but swollen lymph nodes can persist longer.
Less Common and Severe Manifestations
- Severe lymph node swelling leading to rupturing or formation of draining fistulas
- Sore throat or weight loss (less frequent symptoms)
- Loss of appetite, nausea, abdominal pain (rare)
- Bacillary angiomatosis (seen in immunocompromised individuals): abnormal blood vessel growth in skin and organs
- In rare cases, infection may spread to the liver, spleen, bones, eyes (neuroretinitis), or even the heart (endocarditis).
How Is Cat Scratch Disease Diagnosed?
Diagnosis of cat scratch disease relies on a combination of patient history (contact with cats, especially kittens), clinical examination, and laboratory testing if needed.
- History: Recent scratch or bite, exposure to cats, typical symptom development.
- Physical examination: Swollen lymph nodes, local skin lesion, fever, enlarged spleen (rare).
- Laboratory tests (in select cases):
- Blood test for antibodies to Bartonella henselae (immunofluorescence assay, IFA)
- Cultures or PCR tests on blood or lymph node fluid (rarely needed)
- Lymph node biopsy to rule out other causes (done if diagnosis is unclear)
Imaging such as ultrasound or CT may be performed if deep lymph nodes or organ involvement is suspected.
Complications of Cat Scratch Disease
Although cat scratch disease is usually mild, complications can develop, especially in people with weakened immune systems or children. Most healthy individuals recover completely, but rare complications demand prompt medical attention.
- Suppurative lymphadenitis: Lymph nodes become pus-filled and may rupture.
- Bacillary angiomatosis: Abnormal blood vessel growth, sometimes involving skin or internal organs (especially in HIV/AIDS patients).
- Parinaud’s oculoglandular syndrome: Swelling and redness of the eyes along with adjacent lymph node swelling.
- Encephalopathy: Brain inflammation causing seizures, confusion, or even coma (very rare).
- Osteomyelitis: Bone infection.
- Hepatosplenic involvement: Infection of the liver and spleen, presenting as abdominal pain, fever, or weight loss.
- Endocarditis: Infection of the heart valves in those with previous heart disease (extremely rare).
Treatment for Cat Scratch Disease
Most people with cat scratch disease recover fully without specific medical treatment. Symptoms like fever, pain, and lymph node swelling generally improve over time.
- Supportive care: Rest, fluids, and pain relief with acetaminophen or ibuprofen.
- Warm compresses: Apply to swollen lymph nodes to soothe discomfort.
- Antibiotics: Required in severe cases, immunocompromised individuals, or with complications (commonly prescribed drugs include azithromycin or doxycycline).
- Surgical intervention: Rarely needed, only if lymph nodes become extremely swollen or filled with pus that does not resolve.
For immunocompromised patients, longer and more aggressive antibiotic therapy is recommended under close medical supervision.
Treatment of Cats
- Most infected cats remain healthy and do not require treatment unless they exhibit symptoms.
- When treatment is necessary, veterinarians may prescribe antibiotics for 4–6 weeks.
- Controlling fleas on cats (topical or oral flea prevention) is crucial to prevent reinfection and decrease spread.
Prognosis and Recovery
With prompt recognition and appropriate management, the outlook for cat scratch disease is excellent. Most people recover fully within several weeks to a few months. Long-term problems are very uncommon but can arise in those who develop severe complications or who have significant immune suppression.
How Can Cat Scratch Disease be Prevented?
There are several strategies to reduce the risk of cat scratch disease, particularly for children, immunocompromised individuals, and households with kittens.
- Avoid rough play with cats, especially kittens, that could lead to bites or scratches.
- Wash scratches and bites thoroughly with soap and running water immediately.
- Do not allow cats to lick open wounds, sores, or the face.
- Control fleas on cats using veterinarian-approved flea treatments.
- Keep cats indoors as much as possible to limit their exposure to fleas.
- Regularly wash hands after handling cats, especially before touching your face, eyes, or mouth.
- Immunocompromised persons should avoid petting stray cats or kittens.
| Risk Factor | How to Reduce Risk |
|---|---|
| Contact with kittens (under age 1) | Supervise children, gentle interaction, teach safe handling |
| Immunocompromised persons | Avoid young/stray cats, prioritize flea control, prompt wound care |
| Environments with fleas | Use effective flea preventives, keep cats indoors |
| Cats with unknown health | Avoid handling stray or feral cats |
Frequently Asked Questions (FAQs) About Cat Scratch Disease
What is the bacterium that causes cat scratch disease?
The disease is caused by Bartonella henselae, a gram-negative bacterium commonly found in the saliva, claws, and fur of infected cats.
How serious is cat scratch disease?
In most cases, cat scratch disease is mild and self-limited, but it can cause serious illness in people with weakened immune systems, young children, and in rare cases may lead to complications involving organs.
How soon after exposure do symptoms appear?
Symptoms usually appear 3–14 days after a scratch or bite, but sometimes onset may be delayed up to 6 weeks.
Can my cat be treated or tested for this infection?
Most cats carrying Bartonella henselae show no symptoms and do not need treatment. Veterinarians may recommend flea control as the best prevention. Testing is not commonly performed for healthy cats.
What should I do if scratched or bitten by a cat?
- Immediately wash the area with soap and water.
- Monitor for signs of infection, such as swelling, tenderness, or a blister.
- Consult a healthcare provider if the wound worsens, you experience flu-like symptoms, or swollen lymph nodes or rash develops.
Should I get rid of my cat?
No. With proper hygiene, wound care, and veterinary flea management, the risk of transmission is low. Immunocompromised individuals might take extra precautions, but there is generally no need to remove a healthy household pet.
Is cat scratch disease contagious between people?
No. The infection cannot be transmitted directly from person to person. It is only spread through exposure to infected cats or fleas.
Summary
Cat scratch disease is a preventable and typically mild condition for most healthy individuals. By understanding the ways it spreads, recognizing early symptoms, and following prevention guidelines, you can greatly lower the risk for yourself and your family. Regular veterinary care and flea control for pets, prompt wound care, and cautious play—especially with kittens—are key measures to enjoy a safe and rewarding relationship with cats while minimizing health concerns.
References
- https://www.webmd.com/skin-problems-and-treatments/cat-scratch-fever
- https://www.stlouischildrens.org/conditions-treatments/cat-scratch-disease
- https://www.ncbi.nlm.nih.gov/books/NBK482139/
- https://medlineplus.gov/ency/article/001614.htm
- https://www.petmd.com/cat/conditions/infectious-parasitic/cat-scratch-fever-cats-what-it-and-how-it-treated
- https://my.clevelandclinic.org/health/diseases/23537-cat-scratch-fever
- https://www.aafp.org/pubs/afp/issues/2011/0115/p152.html
- https://www.cdc.gov/bartonella/about/about-bartonella-henselae.html
- https://www.sahealth.sa.gov.au/wps/wcm/connect/public+content/sa+health+internet/conditions/infectious+diseases/cat+scratch+disease/cat-scratch+disease+-+including+symptoms+treatment+and+prevention
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