City sanitation and socioeconomics predict rat zoonotic infection across diverse neighbourhoods.

Rat-associated zoonoses transmitted through faeces or urine are of particular concern for public health because environmental exposure in homes and businesses may be frequent and undetected. To identify times and locations with greater public health risks from rats, we investigated whether rat characteristics, environmental features, socioeconomic factors, or season could predict rat infection risk across diverse urban neighbourhoods. In partnership with a pest management company, we sampled rats in 13 community areas along an income gradient in Chicago, a large city where concern about rats has increased in recent years. We collected kidneys forLeptospiraspp. testing and colon contents for aerobic bacteria such asSalmonellaspp. andEscherichia coli. Of 202 sampled rats, 5% carriedLeptospiraspp. and 22% carriedE. coli. Rats were significantly more likely to carryLeptospiraspp. on blocks with more standing water complaints in higher-income neighbourhoods (OR = 6.74, 95% CI: 1.54-29.39). Rats were significantly more likely to carryE. colion blocks with more food vendors (OR = 9.94, 2.27-43.50) particularly in low-income neighbourhoods (OR = 0.26, 0.09-0.82) and in the spring (OR = 15.96, 2.90-88.62). We detected a high diversity ofE. coliserovars but none contained major virulence factors. These associations between environmental features related to sanitation and infection risk in rats support transmission through water forLeptospiraspp. and faecal-oral transmission forE. coli. We also found opposing relationships between zoonotic infection risk and income for these two pathogens. Thus, our results highlight the importance of sanitation for predicting zoonotic disease risks and including diverse urban areas in pathogen surveillance to mitigate public health risks from rats.