Bartonella henselae as a cause of acute-onset febrile illness in cats

Breitschwerdt, Edward B; Broadhurst, Jack J; Cherry, Natalie A

There is substantial genetic variation among B henselae strains, 24 potentially contributing to different virulence characteristics, most likely mediated by genetic variation among B henselae type IV secretion systems, 25 Bad A adhesion proteins and potentially other unknown virulence factors. 26 Also, the strains most often isolated from healthy, non-clinical cats are not the genetic strains most often found in humans with bartonellosis. 24, 27 Thus, similar to other bacteria such as Escherichia coli (E coli 0157:H7 can induce hemolytic uremic syndrome and death), there are differences in virulence among B henselae strains. One might speculate that virulence differences, in conjunction with the robustness of the host immune response, determine the extent to which a B henselae genotype induces disease. For example, the CSU-1 strain, originally isolated from a shelter cat in Florida and used experimentally by Bradbury and Lappin in flea transmission studies, has induced acute myocarditis in young experimentally infected cats. 9 Other feline experimental infection studies have also provided evidence to support virulence differences among B henselae strains. 4, 9 Granulomatous myocarditis was reported in young, naturally flea-infested cats, by direct bacterial visualization and PCR amplification of B henselae from the myocardial lesions. 28 Thus, future fieldbased studies designed to address disease causation should incorporate bacterial isolation, B henselae genotyping, sequential serological testing, an enrichment culture/PCR approach to enhance the sensitivity of documenting infection with one or more Bartonella species and documentation of each cat's clinical response to a defined antibiotic treatment regimen.