Host-Driven Genetic Diversity of Leptospira in the Americas: A Continental Perspective

Leptospira is a genetically diverse genus of spirochetes comprising over 68 species, including several pathogenic taxa such as L. interrogans, L. santarosai, L. noguchii, and L. weilii. These bacteria infect a wide range of vertebrates, especially mammals, with infected animals serving as renal carriers that excrete the pathogen through urine. While rodents are the primary reservoirs for some species, multiple vertebrate orders participate in Leptospira transmission cycles in the Americas. This study aimed to assess and compare the genetic diversity of Leptospira populations across mammalian hosts throughout their distribution ranges in the Americas, exploring the influence of host interactions on bacterial diversity. Data for this study were obtained from two sources: (1) original screening of bats and rodents for pathogenic Leptospira and (2) partial gene sequences (16S, LipL32, and SecY) retrieved from GenBank, including sequences from human leptospirosis cases. A total of 321 animals were sampled (104 rodents and 217 bats), with an overall infection frequency of 12.1%. Positive samples were identified via BLAST as L. interrogans, L. noguchii, L. santarosai, L. alexanderi, and L. weilii. Genetic diversity metrics were calculated, and haplotype networks were constructed. Overall analyses revealed greater genetic diversity in bat Leptospira sequences, particularly in the SecY gene. In contrast, artiodactyls exhibited high intraspecific variation, suggesting a potential role in generating new Leptospira variants. Marsupials, rodents, and carnivores showed limited Leptospira diversity. These findings offer new insights into the evolutionary dynamics of Leptospira in the Americas and highlight the role of host ecology in shaping pathogen genetic diversity.