Environmental Factors Associated with the Carriage of Bacterial Pathogens in Norway Rats

Worldwide, Norway rats (Rattus norvegicus) carry a number of zoonotic pathogens. Many studies have identified rat-level risk factors for pathogen carriage. The objective of this study was to examine associations between abundance, microenvironmental and weather features and Clostridium difficile, antimicrobial-resistant (AMR) Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA) carriage in urban rats. We assessed city blocks for rat abundance and 48 microenvironmental variables during a trap-removal study, then constructed 32 time-lagged temperature and precipitation variables and fitted multivariable logistic regression models. The odds of C. difficile positivity were significantly lower when mean maximum temperatures were high (≥ 12.89°C) approximately 3 months before rat capture. Alley pavement condition was significantly associated with AMR E. coli. Rats captured when precipitation was low (< 49.40 mm) in the 15 days before capture and those from blocks that contained food gardens and institutions had increased odds of testing positive for MRSA. Different factors were associated with each pathogen, which may reflect varying pathogen ecology including exposure and environmental survival. This study adds to the understanding of how the microenvironment and weather impacts the epidemiology and ecology of zoonotic pathogens in urban ecosystems, which may be useful for surveillance and control activities.