Transmission

Cat scratch disease (CSD), Bartonella henselae

People can get CSD from the scratches of domestic or feral cats, particularly kittens. The disease occurs most frequently in children under 15. Cats can harbor infected fleas that carry Bartonella bacteria. These bacteria can be transmitted from a cat to a person during a scratch. Some evidence suggests that CSD may be transmitted directly to humans by the bite of infected cat fleas, although this has not been proven.

CSD occurs worldwide and may be present wherever cats are found. Stray cats may be more likely than pets to carry Bartonella. In the United States, most cases of CSD occur in the fall and winter.

Ticks may carry some species of Bartonella bacteria, but there is currently no convincing evidence that ticks can transmit Bartonella infection to humans.

Trench fever, Bartonella quintana

Trench fever is transmitted by the human body louse. Because of its association with body louse infestations, trench fever is most commonly associated with homeless populations or areas of high population density and poor sanitation. Trench fever received its name during World War I, when many soldiers fighting in the European trenches harbored infected body lice and became infected with the disease.

Trench fever has a worldwide distribution; cases have been reported from Europe, North America, Africa, and China.

Carrión’s disease, Bartonella bacilliformis

Carrión’s disease, formerly known as bartonellosis, is transmitted by bites from sand flies (genus Lutzomyia) that are infected with the organism. Carrión’s disease has limited geographic distribution; transmission occurs in the Andes Mountains at 3,000 to 10,000 ft in elevation in western South America, including Peru, Colombia, and Ecuador. Most cases are reported in Peru.

A few cases of Oroya fever and verruga peruana (Peruvian warts) have been reported in travelers who returned from the Andean highlands in South America, but the risk is low. In 2007, a newly recognized species of Bartonella (B. rochalimae) was identified in an ill traveler returning from Peru. Much is still unknown regarding the existence of other competent arthropod vectors and the identification of a natural, nonhuman, vertebrate reservoir.