Urban Rats ( Rattus norvegicus ) through a One Health Lens: Social and Ecological Factors Promote Opportunities for Urban Leptospirosis in Rats, Dogs, and People

Living in cities creates One Health challenges because urban environments can promote pathogen transmission in wildlife and human-wildlife interactions with commensal species such as rats. In this study, we examined social and ecological processes that lead to an elevated risk of leptospirosis, a fatal rat-associated disease transmitted through Leptospira interrogans bacteria in urine. We examined rat and human factors associated with (1) human exposure to rat urine in the home environment, (2) the presence of rats carrying L. interrogans on the block, and (3) environmental conditions associated with rat infection. We surveyed residents and trapped rats on the same 16 blocks in four neighbourhoods in Chicago. Survey respondents were more likely to observe rat urine in their homes if they had lower incomes. Blocks where rats were carrying L. interrogans had higher rat abundance and respondents with higher incomes, who reported dogs dying from leptospirosis, children playing in yards with rat waste, flooded yards, and gardens with rat burrows. Rats were more likely to be infected with L. interrogans if they were trapped on a block with more accessible garbage and if they were older. Our results highlight that rat presence alone does not determine the risk of close contact with rat-associated pathogens; socio-economics can affect an individual’s ability to exclude animals from living spaces. In addition, improved waste management may help mitigate disease risks for humans, wildlife, and domestic animals. We also discuss opportunities for public education about rat-associated zoonoses and lessons learned about meaningful community engagement in One Health work.