Gram-negative bacteria in the genus Bartonella. Human illness is primarily caused by Bartonella henselae (cat-scratch disease [CSD]), B. quintana (trench fever), and B. bacilliformis (Carrión disease). A variety of Bartonella spp. can cause culture-negative endocarditis; other clinical syndromes due to Bartonella spp. have also been reported. For example, in 2007, a newly recognized species of Bartonella (B. rochalimae) was identified in an ill traveler returning from Peru.
CSD is contracted through scratches from domestic or feral cats, particularly kittens. CSD may be transmitted directly to humans by the bite of infected cat fleas, although this has not yet been proven. Trench fever is transmitted by the human body louse. Carrión disease is transmitted by sand flies (genus Lutzomyia) that are infected with B. bacilliformis.
CSD and trench fever are distributed worldwide. In the United States, CSD is more common in children, and the incidence peaks from September through January. Trench fever typically occurs in populations that do not have access to proper hygiene, such as refugees and the homeless. Carrión disease has limited geographic distribution; transmission occurs in the Andes Mountains at 1–3 km (0.6–1.9 miles) elevation in western South America, including Peru, Colombia, and Ecuador. Most cases are reported in Peru.
CSD symptoms include fever; enlarged, tender lymph nodes that develop 1–3 weeks after exposure; and a papule or pustule at the inoculation site. Trench fever symptoms include fever, headache, transient rash, and bone pain (mainly in the shins, neck, and back).
Bacillary angiomatosis (caused by B. henselae or B. quintana) and peliosis hepatis (caused by B. henselae) occur primarily in people infected with HIV. Bacillary angiomatosis may present as skin, subcutaneous, or bone lesions. Many Bartonella spp. can cause signs and symptoms of subacute endocarditis, which is often culture-negative.
Carrión disease has 2 distinct phases: an acute phase (Oroya fever) characterized by fever, myalgia, headache, and anemia and an eruptive phase (verruga peruana) characterized by red-to-purple nodular skin lesions.
CSD can be diagnosed clinically in patients with typical presentation and a compatible exposure history. Serology can confirm the diagnosis, although cross-reactivity may limit interpretation. B. henselae DNA may also be detected by PCR or culture of pus or lymph node aspirates by using special techniques.
Trench fever can be diagnosed by isolating B. quintana from blood or by serology. PCR technology is improving the diagnosis of disseminated Bartonella infections. Endocarditis caused by Bartonella spp. can be diagnosed by elevated serology of the patient and by PCR or culture of excised heart valve tissue.
Oroya fever is typically diagnosed via blood culture or direct observation of the bacilli in peripheral blood smears.
Most cases of CSD eventually resolve without treatment, but a small percentage of people will develop disseminated disease with severe complications. The use of antibiotics to shorten the course of disease is debated, although azithromycin speeds the decrease in lymph node volume.
Various antibiotics are effective against Bartonella infections, including penicillins, tetracyclines, cephalosporins, aminoglycosides, and fluoroquinolones. Recommended antibiotic regimens and duration of treatment vary by clinical disease.
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