Bartonellosis is a cat disease that can be passed to people (something known as a zoonosis). The culprit? A bacterium called bartonella — and the cat is its intended host.
Bartonella is so perfectly adapted to living in feline red blood cells that it doesn’t make the cat ill. Infection is passed from cat to cat by flea bites, and people can acquire infection when scratched by a cat whose claws are contaminated with bartonella (or if bitten by the cat).
Bartonellosis in people, often referred to as “cat scratch disease,” is not usually serious unless the person is immunosuppressed, such as the very young or old, those on chemotherapy or people with HIV. Their immune systems are not able to keep the bacteria in check; the bacteria multiply, causing fever and inflammation.
Bartonella likes warm, humid environments — a recent study showed 40% of the cats tested in California were positive for bartonella. The same study suggested that human bartonellosis is a rising problem.
Bartonella is so well adapted to living in the cat that it rarely causes symptoms in this host. Although large numbers of cats may be infected, few show signs of ill health, and in those rare occasions when this happens, the main sign is a short-lived fever.
If a human accidentally becomes infected, usually the signs are mild and self-limiting. These include a fever and enlarged lymph nodes, which settle down after 1–2 weeks.
However, immunosuppressed people are not so well equipped to fight off infection, and the signs can be more severe. Unchecked, bartonella causes inflammation in the tissues it visits, so the patient may suffer from an inflamed heart, brain or eyes.
“Cat scratch disease” is caused by bartonella, a parasite of the red blood cells. It’s passed from one cat to another when a flea feeds and then hops onto another cat for its next meal.
Cats with fleas are usually itchy, and when one scratches, she may draw blood infected with bartonella. If this cat then scratches a person, he may become accidentally infected.
It is not possible for a person to catch bartonellosis from the bite of a flea that has fed on an infected cat.
There are no typical changes on a routine blood panel that can identify a cat as infected with bartonella. Even though bartonella parasitizes red blood cells, it may not show up on a blood smear because special stains are required.
The gold standard for confirming bartonellosis in cats is culture of the organism from the patient’s blood. However, infection waxes and wanes, and so, bartonella may not be present when a sample is taken, which means a false-negative result is possible, even in an infected cat.
Testing is simpler in people because a PCR test or serology of a blood sample can prove the presence of bartonella.
Because bartonellosis rarely causes illness in cats, whether it is worth treating infected animals or not is debatable. If treatment is necessary, then a number of antibiotics, including those from the oxytetracycline and flouroquinolone families, are highly effective.
Controlling cat-to-cat spread is a matter of maintaining good parasite control with a product effective at killing adult fleas.
People can minimize the risk of infection by avoiding rough play with cats where they are likely to get scratched. If a person does get bitten or scratched, then wash the wound immediately with soap and plenty of flowing water.
- “Bartonella henselae an emerging important zoonosis.” AM Wolf. Consultations in Feline Medicine. Publisher: WB Saunders.
- “Cat scratch disease: An update.” Groves, Hoskins & Harrington. Comp Cont Ed Prac Vet, 15: 441–448.
- “Prevalence of Bartonella henselae antibodies in serum of cats with and without clinical sings of central nervous system disease.” Pearce, Radecki, Brewer & Lappin. J Fel Med & Surg. *: 315–320.
This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Oct. 2, 2015.