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Land use change can elevate disease risk by creating conditions beneficial to species that carry zoonotic pathogens. Observations of concordant global trends in increased pathogen prevalence or disease incidence and landscape change have generated concerns that urbanization could increase transmission risk of some pathogens. Yet host-pathogen relationships underlying transmission risk have not been well characterized within cities, even where contact between humans and species capable of transmitting pathogens of concern occurs. We addressed this deficit by testing the hypothesis that areas in cities experiencing greater population loss and infrastructure decline (i.e., counter-urbanization) can support a greater diversity of host species and a larger and more diverse pool of pathogens. We did so by characterizing pathogenic Leptospira infection relative to rodent host richness and abundance across a mosaic of abandonment in post-Katrina New Orleans (Louisiana, USA). We found that Leptospira infection loads were highest in areas that harboured increased rodent species richness (which ranged from one to four rodent species detected). Areas with greater host co-occurrence also harboured a greater abundance of hosts, including the host species most likely to carry high infection loads, indicating that Leptospira infection can be amplified by increases in overall and relative host abundance. Evidence of shared infection among rodent host species indicates that cross-species transmission of Leptospira probably increases infection at sites with greater host richness. Additionally, evidence that rodent co-occurrence and abundance and Leptospira infection load parallel abandonment suggests that counter-urbanization can elevate zoonotic disease risk within cities, particularly in underserved communities that are burdened with disproportionate concentrations of derelict properties., (© 2020 John Wiley & Sons Ltd.)

Four spirochetes (F1 T , B21, Yale T and AMB6-RJ) were isolated from environmental sources: F1 T and B21 from soils of an urban slum community in Salvador (Brazil), Yale T from river water in New Haven, Connecticut (USA) and AMB6-RJ from a pond in a horse farm in Rio de Janeiro (Brazil). Isolates were helix-shaped, aerobic, highly motile and non-virulent in a hamster model of infection. Draft genomes of the strains were obtained and analysed to determine the relatedness to other species of the genus Leptospira . The analysis of 498 core genes showed that strains F1 T /B21 and Yale T /AMB6-RJ formed two distinct phylogenetic clades within the 'Pathogens' group (group I). The average nucleotide identity (ANI) values of strains F1 T /B21 and Yale T /AMB6-RJ to other previously described Leptospira species were below <84 % and <82 %, respectively, which confirmed that these isolates should be classified as representatives of two novel species. Therefore, we propose Leptospirayasudae sp. nov. and Leptospirastimsonii sp. nov. as new species in the genus Leptospira . The type strains are F1 T (=ATCC-TSD-163=KIT0259=CLEP00287) and Yale T (=ATCC-TDS-162=KIT0258=CLEP00288), respectively.