Human Bartonellosis: Perspectives of a Veterinary Internist

Bartonella species are fastidious gram-negative bacteria that are highly adapted to a mammalian reservoir host and within which the bacteria usually cause a long-lasting intraerythrocytic bacteremia. These facts are of particular importance to veterinarians and physicians, as an increasing number of animal reservoir hosts have been identified for various Bartonella species. Among numerous other examples, Bartonella henselae has co-evolved with cats, Bartonella vinsonii subsp. berkhoffii has co-evolved with dogs and wild canines, and Bartonella bovis has co-evolved with cattle. Importantly, the list of reservoir-adapted Bartonella species, including a large number of rodent species that might serve as “pocket pets,” continues to grow exponentially, as new Bartonella spp. are discovered. Prior to 1990, there were only two named Bartonella species, whereas there are now at least 24 named and numerous unnamed or candidatus species, based upon deposited Gen Bank sequences or preliminary reports, respectively, seventeen Bartonella spp. including B. alsatica, B. bacilliformis, B. clarridgeiae, B. doshiae, B. elizabethae, B. grahamii, B. henselae (Houston 1 and San Antonio 2 strains), B. koehlerae, B. melophagi, B. quintana, B. rochalimaea, B. tamiae, B. vinsonii subsp. berkhoffii (Genotypes I, II and III), and B. washoensis have been associated with an expanding spectrum of human diseases.