About Bartonella

Key points

  • Bartonella bacteria are spread to humans by fleas, body lice, sand flies, or contact with flea-infested animals.
  • There is no evidence that ticks spread Bartonella infection to people.
  • Cat scratch disease is the most common form of bartonellosis in the United States.


Several species of Bartonella bacteria cause disease in people. Infection with any one of these bacteria is referred to broadly as bartonellosis, although some forms of infection also have common names (for example, cat scratch disease).

For more information:

Image of a flea
B. henselae is transmitted by the scratch of domestic or feral cats. Cats can have fleas that carry the bacteria.
Image of a human body louse
B. quintana is transmitted by the human body louse.
Image of a sand fly
B. bacilliformis is transmitted by bites from infected sand flies.

There is no evidence that Bartonella species can be transmitted to people by ticks. Transmission studies with ticks have only used mice and artificial feeding systems which do not demonstrate that a tick can spread bacteria to people or that the bacteria can survive in a tick for any length of time.