Cat Scratch Disease: Bartonella Infection in Cats and Dogs
Cat scratch disease (bartonellosis) is a bacterial infection spread by fleas that can affect cats, dogs, and their owners. Learn how it spreads and how to prevent it.
Cat scratch disease (CSD), also called bartonellosis, is a bacterial infection caused by Bartonella henselae. The bacteria circulate among cats — especially kittens — and are spread between cats by fleas. Most infected cats show no signs at all and act as healthy carriers. The condition matters most as a zoonotic disease: people can develop cat scratch disease after a scratch or bite from an infected cat. Good flea control is the single most effective way to break the cycle.
Key Points
- Cat scratch disease is caused by the bacterium Bartonella henselae
- Fleas spread the bacteria between cats — the flea is the key link
- Most infected cats appear completely healthy
- Kittens and flea-infested cats are most likely to carry it
- People can develop swollen lymph nodes and fever after a scratch or bite
- Strict flea control is the most effective prevention
How It Spreads
Bartonella henselae lives in the bloodstream of infected cats. Fleas feed on an infected cat, then pass the bacteria to other cats through their droppings (flea dirt), which contaminate scratches and wounds during grooming. Cats spread the infection to people when bacteria-laden flea dirt on their claws or in their saliva enters a person's skin through a scratch or bite. The bacteria are not spread directly from person to person.
Signs in Cats
The large majority of infected cats show no symptoms and remain healthy carriers for months. When signs do occur — more often in kittens or cats with weakened immune systems — they can include mild fever, lethargy, swollen lymph nodes, and occasionally inflammation of the eyes, gums, or heart. Because most cats appear normal, infection usually goes unnoticed unless a person in the household develops cat scratch disease.
Risk to People
In people, cat scratch disease typically begins with a small bump or blister at the scratch site, followed by swollen, tender lymph nodes near the wound and a low-grade fever, headache, and fatigue. It is usually mild and self-limiting in healthy adults and children, but it can be more serious in people with weakened immune systems, sometimes affecting the eyes, liver, or heart. Anyone with these signs after a cat scratch should see their doctor.
Diagnosis and Treatment
In cats, diagnosis can be confirmed with blood tests (PCR or culture), though testing healthy cats is not routinely recommended. Most infected cats do not require treatment. When treatment is warranted — for sick cats or to reduce risk to an immunocompromised owner — a course of antibiotics such as doxycycline may be prescribed, alongside aggressive flea control. In people, antibiotics are used for moderate to severe cases.
Prevention
Year-round flea control on all cats in the household is the foundation of prevention — no fleas means almost no transmission. Keep cats' nails trimmed, avoid rough play that leads to scratches and bites, and wash any scratch or bite promptly with soap and water. Adopt cats from environments with good flea management, and keep cats indoors to reduce flea exposure. People with weakened immune systems should be especially careful and may wish to avoid kittens.
When to See a Vet Immediately
- You or a family member develops swollen lymph nodes or fever after a cat scratch or bite
- Your cat has a heavy flea infestation
- An immunocompromised person lives with your cat and you want to assess risk
- Your cat shows swollen lymph nodes, persistent fever, or red, inflamed eyes
- You are adopting a new kitten and want a flea-control and wellness plan
How RVC Can Help
RVC can set up an effective, year-round flea-control program for every cat in your home — the key to preventing cat scratch disease — and advise households with immunocompromised members on reducing risk. If your cat is unwell or you have questions about bartonellosis, our team is available 24/7 to help.
This article is for educational purposes only and does not replace professional veterinary advice. If your pet is showing any symptoms, please contact Royal Veterinary Center immediately at +853 6677 6611.