Bartonella Infection: Cat Scratch Disease

Laurie Anne Walden, DVM

Photo by Bogdan Farca on Unsplash

Cat scratch disease in humans is caused by infection with Bartonella henselae bacteria, which are transmitted by cat fleas. This potentially serious infection is an important reason to use flea control products for all cats all year round.
 
Transmission
Bartonella species are spread by arthropods such as fleas, lice, and sand flies. People can be infected by several species of Bartonella. In the United States, B henselae is the most common cause of disease in humans.
 
Cat fleas shed B henselae in their feces. Cats that harbor fleas carry these bacteria on their claws, on their skin, and in their mouths. Humans are usually infected by cat scratches contaminated with flea feces. People can also be infected by being bitten or having an open wound licked by a cat carrying B henselae.
 
Dogs can also carry B henselae, but they typically have a lower bacterial load than cats. Whether dogs can transmit the infection to humans is not known.
 
Infection in Humans
In humans, B henselae infection can cause fever and swollen lymph nodes. More rarely, it causes inflammation of the heart valves, brain, bone, joints, eyes, or other organs. People with compromised immunity, such as those with HIV infection, are more likely than others to develop serious illness from B henselae infection.
 
Infection in Cats
Cats very commonly carry B henselae. Up to 40% of shelter cats in some geographic locations have B henselae in their bloodstream. Kittens tend to carry more bacteria than adult cats.
 
Cats carrying B henselae usually have no symptoms. Because these bacteria are well adapted to living in cats’ bodies, they very rarely make cats sick. However, some cats develop fever, vomiting, eye inflammation, or swollen lymph nodes.
 
Bartonella infection can be difficult to diagnose in cats. No antibiotic has been shown to completely eliminate the bacteria from carrier cats, and prolonged antibiotic treatment can cause the bacteria to develop antibiotic resistance. For these reasons, testing and treatment are recommended only for cats that have signs of illness caused by Bartonella infection.
 
Prevention
Because flea control prevents B henselae transmission among cats, the American Association of Feline Practitioners recommends that all cats receive flea prevention products year round.
 
The CDC recommends these steps to prevent B henselae infection in people:

• Avoid being scratched, bitten, or licked by cats, especially stray cats and kittens. The risk is highest for people with compromised immunity.
• Wash cat scratch wounds with soap and water.
• People with compromised immunity should wash their hands after handling cats.
• Use flea control products that your veterinarian recommends for your cat.
• Keep cats indoors to reduce the chance of flea exposure.
• People with compromised immunity can keep their cats and do not need to have healthy cats tested or treated for Bartonella.
• People with compromised immunity should avoid adopting cats younger than 1 year, stray cats, sick cats, and cats with fleas.

Sources

• Bartonella henselae infection or cat scratch disease (CSD). Centers for Disease Control and Prevention. Reviewed January 10, 2022. Accessed July 6, 2023. https://www.cdc.gov/bartonella/bartonella-henselae/index.html

• Lappin MR, Elston T, Evans L, et al. 2019 AAFP feline zoonoses guidelines. J Feline Med Surg. 2019;21(11):1008-1021. doi:10.1177/1098612X19880436

Image source: https://unsplash.com/photos/CEx86maLUSc

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