The currently accepted model explaining the infection cycle holds that the transmitting vectors are
blood-suckingarthropods and the
reservoir hosts are
mammals. Immediately after infection, the bacteria colonize a primary niche, the
endothelial cells. Every five days, some of the Bartonella bacteria in the endothelial cells are released into the blood stream, where they infect
erythrocytes. The bacteria then invade a
phagosomal membrane inside the erythrocytes, where they multiply until they reach a critical population density. At this point, they simply wait until they are taken up with the erythrocytes by a blood-sucking arthropod.[citation needed]
Though some studies have found "no definitive evidence of transmission by a tick to a
vertebrate host,"[8][9]Bartonella species are well-known to be transmissible to both animals and humans through various other vectors, such as fleas, lice, and sand flies.[10][11]Bartonella bacteria are associated with cat-scratch disease, but a study in 2010 concluded, "Clinicians should be aware that ... a history of an animal scratch or bite is not necessary for disease transmission."[12] All current Bartonella species identified in canines are human pathogens.[13]
Pathophysiology
Bartonella infections are remarkable in the wide range of symptoms they can produce. The course of the diseases (acute or chronic) and the underlying pathologies are highly variable.[14]
Treatment is dependent on which species or strain of Bartonella is found in a given patient. While Bartonella species are susceptible to a number of standard antibiotics in vitro—
macrolides and
tetracycline, for example—the efficacy of antibiotic treatment in immunocompetent individuals is uncertain.[14] Immunocompromised patients should be treated with antibiotics because they are particularly susceptible to systemic disease and bacteremia. Drugs of particular effectiveness include
trimethoprim-sulfamethoxazole,
gentamicin,
ciprofloxacin, and
rifampin; B. henselae is generally resistant to
penicillin,
amoxicillin, and nafcillin.[14]
Epidemiology
Homeless intravenous drug users are at high risk for Bartonella infections, particularly B. elizabethae. B. elizabethae seropositivity rates in this population range from 12.5% in
Los Angeles,[19] to 33% in
Baltimore, Maryland,[20] 46% in
New York City,[21] and 39% in
Sweden.[22]
^Walker DH (1996).
"Rickettsiae". In Baron S, et al. (eds.). Rickettsiae. In: Barron's Medical Microbiology (4th ed.). Univ of Texas Medical Branch.
ISBN978-0-9631172-1-2.
^Vilcins I, Kosoy M, Old JM, Deane EM (2009). Bartonella-like DNA detected in Ixodes ticks (Acari: Ixodida) infesting koalas (Phascolarctos cinereus) in Victoria, Australia. Vector-Borne & Zoonotic Diseases. 9(5), 499-503. DOI: 10.1089/vbz.2008.0132
^Comer JA, Flynn C, Regnery RL, Vlahov D, Childs JE (1996). "Antibodies to Bartonella species in inner-city intravenous drug users in Baltimore, Md". Arch. Intern. Med. 156 (21): 2491–5.
doi:
10.1001/archinte.156.21.2491.
PMID8944742.
^Comer JA, Diaz T, Vlahov D, Monterroso E, Childs JE (2001). "Evidence of rodent-associated Bartonella and Rickettsia infections among intravenous drug users from Central and East Harlem, New York City". Am. J. Trop. Med. Hyg. 65 (6): 855–60.
doi:
10.4269/ajtmh.2001.65.855.
PMID11791987.
S2CID22138835.