Bartonella seroprevalence in rural Thailand.

We estimated the prevalence of anti-Bartonella antibodies among febrile and non-febrile patients presenting to community hospitals in rural Thailand from February 2002 through March 2003. Single serum specimens were tested for IgG titers to four Bartonella species, B. henselae, B. quintana, B. elizabethae and B. vinsonii subsp vinsonii using an indirect immunofluorescent assay. A titer 21:256 was considered positive. Forty-two febrile patients (9.9%) and 19 non-febrile patients (19%) had positive serology titers to at least one Bartonella species. Age-standardized Bartonella seroprevalence differed significantly between febrile (10%) and non-febrile patients (18%, p=0.047), but did not differ by gender. Among all 521 patients, IgG titers 21:256 to B. henselae were found in 20 participants (3.8%), while 17 (3.3%) had seropositivity to B. quintana, 51 (9.8%) to B. elizabethae, and 19 (3.6%) to B. vinsonii subsp vinsonii. These results suggest exposure to Bartonella species is more common in rural Thailand than previously suspected.

Fine-scale identification of the most likely source of a human plague infection.

We describe an analytic approach to provide fine-scale discrimination among multiple infection source hypotheses. This approach uses mutation-rate data for rapidly evolving multiple locus variable-number tandem repeat loci in probabilistic models to identify the most likely source. We illustrate the utility of this approach using data from a North American human plague investigation.

Bartonella tamiae sp. nov., a newly recognized pathogen isolated from three human patients from Thailand.

Three strains of a novel Bartonella species (Bartonella tamiae) were isolated from human patients from Thailand. Sequence analysis of six chromosomal regions (16S rRNA, gltA, groEL, ftsZ, rpoB, and the intergenic spacer region) and phenotypical analysis supported the similarity of the three strains and placed them within the genus Bartonella separately from previously described species.

A longitudinal study of Bartonella infection in populations of woodrats and their fleas.

Rodent-borne bartonellae have been identified as human pathogens. Little is known about Bartonella infections in woodrat hosts and their fleas and how woodrat-flea associations may affect the dynamics of Bartonella infections. We collected blood samples and fleas from two species of woodrats (Neotoma micropus and N. albigula) from Santa Fe County, NM, from 2002-2005. The most predominant flea species were Orchopeas sexdentatus and O. neotomae. Bartonella prevalence in woodrats was 64% overall, with a lower prevalence occurring in the pre-reproductive period compared to the early and late reproductive periods. A negative correlation between Bartonella prevalence in N. micropus and weight of N. micropus was observed. Flea load in Neotoma species was highest in the early reproductive period compared to the pre- and late reproductive periods and was higher in N. micropus compared to N. albigula. Bartonella prevalence in fleas was highest in the early reproductive period and lowest in the late reproductive period, and it was higher in fleas collected from N. micropus than in fleas collected from N. albigula. Abundance of O. sexdentatus was significantly higher in N. micropus compared to N. albigula, and abundance of O. sexdentatus and O. neotomae was highest in the early reproductive period. No direct correlations were found either between Bartonella prevalence in woodrats and in fleas or between Bartonella prevalence in woodrats and flea loads. Out of 25 partially characterized Bartonella isolates from Neotoma woodrats, 24 belonged to one genogroup based on sequencing of the gltA gene.

Identification of Bartonella infections in febrile human patients from Thailand and their potential animal reservoirs.

To determine the role of Bartonella species as causes of acute febrile illness in humans from Thailand, we used a novel strategy of co-cultivation of blood with eukaryotic cells and subsequent phylogenetic analysis of Bartonella-specific DNA products. Bartonella species were identified in 14 blood clots from febrile patients. Sequence analysis showed that more than one-half of the genotypes identified in human patients were similar or identical to homologous sequences identified in rodents from Asia and were closely related to B. elizabethae, B. rattimassiliensis, and B. tribocorum. The remaining genotypes belonged to B. henselae, B. vinsonii, and B. tamiae. Among the positive febrile patients, animal exposure was common: 36% reported owning either dogs or cats and 71% reported rat exposure during the 2 weeks before illness onset. The findings suggest that rodents are likely reservoirs for a substantial portion of cases of human Bartonella infections in Thailand.