Microbiology and Epidemiology

B. henselae is the principal etiologic agent of CSD, although other Bartonella species may rarely be involved. Consistent with the disease's name, contact with apparently healthy cats (being scratched, bitten, or licked), and especially with kittens, is the primary source of infection. Adults are affected nearly as frequently as children. In the United States, the estimated incidence is ∼4-10 cases per 100,000 population.

Bacillary Angiomatosis and Peliosis

Bacillary angiomatosis is caused by B. henselae and B. quintana, while peliosis is caused only by the former species. These diseases occur most often in HIV-infected pts with CD4+ T cell counts of <100/µL.

• Pts with bacillary angiomatosis present with one or more painless skin lesions that may be tan, red, or purple in color. SC masses or nodules, ulcerated plaques, and verrucous growths also occur. Painful osseous lesions, primarily in the long bones, may develop and appear as lytic lesions on radiography.
• Peliosis is an angioproliferative disorder characterized by blood-filled cystic structures that affects primarily the liver but also the spleen and lymph nodes. Hypodense hepatic areas are usually evident on imaging.
• Both diseases are diagnosed on histologic grounds. Blood cultures may be positive.

Trench Fever

• Trench fever (5-day fever) is caused by B. quintana, which is spread by the human body louse to its only animal reservoir: humans.
• Much less common today than in the trenches of World War I, the disease now primarily affects homeless people.
• After a usual incubation period of 15-25 days, disease classically ranges from a mild febrile illness to a recurrent or protracted and debilitating disease. Fever is often periodic, with episodes of 4-5 days separated by ∼5-day afebrile periods.
• Diagnosis requires identification of B. quintana in blood cultures.
• Untreated, the disease usually lasts 4-6 weeks. Death is rare.

Bartonella Endocarditis

Bartonella species (typically B. quintana or B. henselae) are an important cause of culture-negative endocarditis. The disease's manifestations are similar to those of subacute endocarditis of any etiology (Chap. 83 Infective Endocarditis). Even if incubated for prolonged periods (up to 6 weeks), blood cultures are positive in only ∼25% of cases. Serologic or PCR testing for Bartonella in cardiac valve tissue can help establish the diagnosis in pts with negative blood cultures.

Carrión's Disease (Oroya Fever and Verruga Peruana)

Carrion's disease is a biphasic disease caused by B. bacilliformis, which is transmitted by a sandfly vector found in the Andes valleys of Peru, Ecuador, and Colombia.

• Oroya fever is the initial, bacteremic, systemic form, and verruga peruana is its late-onset, eruptive manifestation.
• Oroya fever may present as a nonspecific bacteremic febrile illness without anemia or as acute, severe hemolytic anemia with hepatomegaly and jaundice of rapid onset.
  • In verruga peruana, red, hemangioma-like, cutaneous vascular lesions of various sizes appear either weeks to months after systemic illness or with no previous suggestive history. The lesions persist for months up to 1 year.
• In systemic illness, Giemsa-stained blood films may show typical intraerythrocytic bacilli, and blood and bone marrow cultures are positive. Serologic assays may be helpful. Biopsy may be required to confirm the diagnosis of verruga peruana.