Bartonella henselae is a promiscuous Gram-negative bacterium that infects both cats and humans. When cats are infected, they show no symptoms, thus making it difficult for researchers to identify the disease. It is estimated that there are at least 24,000 cases of Cat Scratch Disease per year in the U.S. in humans.
The bacterium has different effects on immunocompromised individuals, such as AIDS patients, and immunocompetent individuals. In both types of people, bacteremia occurs, which is the presence of bacteria in the blood.
In immunocompetent individuals, Bartonella henselae can cause Cat Scratch Disease (CSD). Bartonella henselae is known to be the agent of bacillary angiomatosis, peliosis hepatitis, septicemia, endocarditis, recurring fever, and neurological disorders. The latter symptoms are fatal when misdiagnosed and improperly treated.