| Summary: | Bartonella species are fastidious Gram negative vector-borne bacteria with a wide range of mammalian
reservoirs. While it is understood that some species Bartonella are human pathogens, the extent of
human exposure to Bartonella species (both pathogenic and non-pathogenic) has yet to be fully
understood. To this end, residual sera from participants enrolled in undifferentiated fever studies in
Cambodia, Ghana, Laos, and Peru were screened for the presence of IgG antibodies against B. quintana
and B. henselae, using the FOCUS diagnostics Dual Spot- Bartonella IgG Immunofluorescence assay.
Forty-eight patients with suspected or confirmed B. bacilliformis exposure or infection in Peru, were
screened to assess cross-reactivity of the FOCUS assay for IgG against other Bartonella species. Ten of 13
patients with confirmed B. bacilliformis infection were Bartonella-specific IgG positive and overall, 36/48
of the samples were positive. Additionally, 79/206, 44/200, 101/180, and 57/100 of samples from Peru,
Laos, Cambodia, and Ghana, respectively were Bartonella-specific IgG positive. Further, ectoparasites
pools from Cambodia, Laos, and Peru were tested using quantitative real-time PCR (qPCR) for the
presence of Bartonella DNA. Of the sand-fly pools collected in Peru, 0/196 were qPCR positive; 15/140
flea pools collected in Cambodia were qPCR positive; while 0/105 ticks, 0/22 fleas, and 0/3 louse pools
collected in Laos tested positive for Bartonella DNA. Evidence of Bartonella in fleas from Cambodia
supports the possibility that humans are exposed to Bartonella through this traditional vector. However,
Bartonella species were not found in fleas, ticks, or lice from Laos, or sandflies from Peru. This could
account for the lower positive serology among the population in Laos and the strictly localized nature of
B. bacillformis infections in Peru. Human exposure to Bartonella species and Bartonella as a human
pathogen warrants further investigation.
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