Diversity of bat-associated Leptospira in the Peruvian Amazon inferred by bayesian phylogenetic analysis of 16S ribosomal DNA sequences

Abstract

The role of bats as potential sources of transmission to humans or as maintenance hosts of leptospires is poorly understood. We quantified the prevalence of leptospiral colonization in bats in the Peruvian Amazon in the vicinity of Iquitos, an area of high biologic diversity. Of 589 analyzed bats, culture (3 of 589) and molecular evidence (20 of 589) of leptospiral colonization was found in the kidneys, yielding an overall colonization rate of 3.4%. Infection rates differed with habitat and location, and among different bat species. Bayesian analysis was used to infer phylogenic relationships of leptospiral 16S ribosomal DNA sequences. Tree topologies were consistent with groupings based on DNA-DNA hybridization studies. A diverse group of leptospires was found in peri-Iquitos bat populations including Leptospira interrogans (5 clones), L. kirschneri (1), L. borgpetersenii (4), L. fainei (1), and two previously undescribed leptospiral species (8). Although L. kirschenri and L. interrogans have been previously isolated from bats, this report is the first to describe L. borgpetersenii and L. fainei infection of bats. A wild animal reservoir of L. fainei has not been previously described. The detection in bats of the L. interrogans serovar Icterohemorrhagiae, a leptospire typically maintained by peridomestic rats, suggests a rodent-bat infection cycle. Bats in Iquitos maintain a genetically diverse group of leptospires. These results provide a solid basis for pursuing molecular epidemiologic studies of bat-associated Leptospira, a potentially new epidemiologic reservoir of transmission of leptospirosis to humans.

Figure 1

Phylogenetic tree based on 16S ribosomal DNA gene sequences using Bayesian analysis showing the 50% majority rule consensus of 29,000 trees from Markov Chain Monte Carlo sampling. Bayesian posterior probabilities are given above the node. Shaded boxes show individual subgroups: A = pathogenic strains; B = intermediate strains; and C = saprophytic strains. Nodes with less than 50% bootstrap support are indicated by an asterisk. Iquitos is the urbanized center of Iquitos. Peña Negra is a patch of mature forest surrounded by second-growth forest. Varillal is mature forest and second-growth forest. La Habana is second-growth forest and a cultivated area. Moralillo is mature and second-growth forest along the Iquitos-Nauta Highway. Highlighted (bold type) clones were detected in bats caught in Iquitos.

Figure 2

Bootstrap 50% majority rule consensus tree generated by weighted parsimony analysis of 1,000 pseudoreplicates. Bootstrap proportions appear above selected nodes. Hightlighted (bold type) clones were detected in bats caught in Iquitos.