Description

• Fastidious intracellular anaerobic gram-negative bacilli:
  • >30 distinct species, at least 13 known to cause disease in humans (1,2)
  • Bartonella henselae and Bartonella quintana are most common in North America.
• Infections manifest in two broad categories:
  • Localized skin lesions and prominent regional lymphadenitis (cat-scratch disease [CSD])
  • Bacteremia with localized vascular lesions in various organs with potential for persistent disseminated infection
• System(s) affected: cardiovascular, gastrointestinal (GI), heme/lymphatic/immunologic, hepatic, musculoskeletal, nervous, pulmonary, skin/exocrine, ocular, renal (rare)
• Synonym(s): bartonellosis; CSD; trench fever; Carrión disease; Oroya fever

Epidemiology

Incidence

• CSD: 9/100,000 annually in the United States (~25,000 cases)
• Carrión disease: 12.7/100 person-years in endemic areas (Andes Mountains); rare in the United States
• Endocarditis: estimated 3–4% of cases
• Others: unknown

Prevalence

• Worldwide
• Seroprevalence studies of B. henselae suggest that many childhood infections are asymptomatic:
  • Seroprevalence in domestic cats is 25–51%.
  • Highest in fall and winter
• Seroprevalence of B. quintana in homeless populations is ~10%.

Etiology and Pathophysiology

• Erythrocyte and endothelial cell invasion
• In immunocompetent hosts, disease progresses to granuloma and suppuration of lymph nodes.
• In immunocompromised hosts, can lead to angiogenesis with mixed inflammatory cell infiltrate

Genetics
No known genetic predisposition

Risk Factors

• Vector exposure with cutaneous inoculation
  • B. henselae (CSD): domestic cat scratch/bite or transmitted horizontally from cat fleas and ticks
    • Natural reservoir is the domestic cat.
    • Transmission from dogs has been reported.
  • B. quintana (trench fever): human body louse, most common in alcohol-dependent homeless males, possible flea (from rats and cats) vector
  • Bartonella bacilliformis (Carrión disease): Lutzomyia sandflies from Andean South America
• Cell-mediated immune dysfunction (particularly in bacillary angiomatosis/bacillary peliosis)
  • HIV infection (CD4⁺ lymphocyte count <100/μL)
  • Chronic steroid use, immunosuppression, or alcohol abuse
• Vector control
  • Treat pets with regular flea/tick medications (3)[B].
  • Avoid stray cats (3)[B].
  • Avoid cat scratches (no rough play with cats); immediately wash cat bite and scratches (3)[B].
  • Do not allow cats to lick open wounds (3)[B].
  • Treat body louse infestations (3)[A].
  • Severely immunosuppressed patients should weigh risks of cat ownership and consider avoiding cats <1 year of age (3)[B].
• No evidence for effectiveness of postexposure chemoprophylaxis (3)[C]
• No evidence for routine testing of cats