Identification of Leptospira strains and modeling of interaction between animal and human hosts and the environment using pairwise sequence alignment

Leptospirosis, a zoonotic disease that affects both humans and other animals, is caused by the ingestion of Lepstospira bacteria, usually through contaminated water or soil. The risk of human infection is increased with close proximity to livestock, rodents, and poor sanitation. The purpose of this study was to determine the genetic similarity of Leptospira samples isolated from human, domestic animal, and rodent blood, as well as water samples from the local environment. Human and animal serology was conducted as part of a sero-prevalence study in urban, peri-urban, and rural communities in Chile. Samples that tested positive for Leptospira infection were then sequenced using PCR and submitted to the National Center for Biotechnology Information BLAST database for strain identification. Sequences were pairwise aligned and given a similarity score using CLUSTAL W, and through hierarchical clustering, a phylogenetic tree was produced. The phylogenetic tree was then used to characterize the diversity of serovars in rodents and water in each community, and to determine the level of relatedness of those serovars to the Leptospira isolates from humans and domestic animals. Noting which serovars are retained exclusively in the environment, animal, or human hosts, and which are shared will assist in modeling the transmission dynamics of Leptospirosis. Future direction on this project includes spatial mapping of the positive serologic and environmental samples, and in conjunction with the identification of particular serovar types and their potential hosts, will help design more targeted public health interventions for individual communities.