Bartonella bacteria cause several diseases in humans. The three most common are cat scratch disease, caused by B. henselae; trench fever, caused by B. quintana; and Carrión's disease, caused by B. bacilliformis.
Prevention
Cat scratch disease (CSD), Bartonella henselae

• Avoid rough play with cats, particularly strays and kittens, to prevent scratches. This is especially important for immunocompromised individuals. Wash hands promptly after handling cats.
• Treat cats for fleas using fipronil and other spot-on treatments. Check with your veterinarian. Permethrin should not be used on cats.
• Use a flea collar or similar topical preventive on dogs (fipronil, methoprene, imidocloprid, or permethrin), especially if you have both cats and dogs in your household.
• Keep cats indoors and away from stray cats. 

Trench fever, Bartonella quintana

• Avoid exposure to human body lice. Body lice are typically associated with conditions of crowding and limited access to proper personal hygiene.

Carrión's disease, Bartonella bacilliformis

• Use repellents and protective clothing to avoid sand fly bites in areas where Carrión's disease is common (South America). If possible, limit outdoor activities at dawn and dusk, when sand flies are most active.

Symptoms
Cat scratch disease (CSD), Bartonella henselae

• Fever
• Enlarged, tender lymph nodes that develop 1–3 weeks after exposure
• A papule or pustule at the inoculation site

Rarely, unusual manifestations such as eye infections, severe muscle pain, or encephalitis may occur.
Trench fever, Bartonella quintana

• Fever (may present as a single bout of fever or bouts of recurrent fever)
• Headache
• Rash
• Bone pain, mainly in the shins, neck, and back

Carrión's disease, Bartonella bacilliformis
This disease has 2 distinct phases:

• Oroya fever: During this phase, patients may present with fever, headache, muscle aches, abdominal pain, and severe anemia.
• Verruga peruana: During this later phase, lesions appear under the skin as nodular growths, then emerge from the skin as red-to-purple vascular lesions that are prone to ulceration and bleeding.

Other complications
Bacillary angiomatosis
Bacillary angiomatosis (caused by B. henselae or B. quintana) and bacillary peliosis (caused by B. henselae) occur primarily in immunocompromised people, such as those with advanced HIV infection. Bacillary angiomatosis may present as lesions in the skin, subcutaneous tissue, bone, or other organs. Bacillary peliosis causes vascular lesions in the liver and spleen.
Subacute endocarditis
Many Bartonella species can cause subacute endocarditis (infection of the heart valves), which is often culture negative