Culling of Urban Norway Rats and Carriage of Bartonella spp. Bacteria, Vancouver, British Columbia, Canada.

We investigated the effects of culling on Bartonella spp. bacteria carriage among urban rats in Canada. We found that the odds of Bartonella spp. carriage increased across city blocks except those in which culling occurred. Removing rats may have prevented an increase in Bartonella spp. prevalence, potentially lowering human health risks.

Is Carriage of Leptospira interrogans by Rats Influenced by the Urban Environment or Population Density?

Leptospira interrogans is one of the most important zoonotic pathogens globally. In urban settings, Norway rats (Rattus norvegicus) are important reservoirs of L. interrogans, but it is unclear how this bacterium is transmitted among rats. Both environmental features and rat population density may determine the prevalence of this pathogen in rat populations as well as the spillover risk to people. While these factors could play an important role in transmission between rats, it is unknown whether such factors influence prevalence among rats at a fine scale. Our objective was to determine if carriage of L. interrogans by rats could be explained by variation in the environment or in rat population density. Rats were live-trapped in a single neighborhood of Vancouver, Canada during two study periods (2011-12; 2016-17) and were tested for L. interrogans. The physical environment of each city block was recorded using a comprehensive, in-person environmental survey. Using generalized linear mixed modelling, we found no evidence of an association between carriage of L. interrogans and environmental features or rat population density, suggesting that these were not the primary drivers of its distribution among rats within this neighborhood. Understanding factors that promote L. interrogans transmission can be used to inform management approaches to minimize public health risks.

Methicillin-resistant Staphylococcus aureus in urban Norway rat (Rattus norvegicus) populations: Epidemiology and the impacts of kill-trapping.

Urban Norway rat (Rattus norvegicus) populations can carry the bacteria methicillin-resistant Staphylococcus aureus (MRSA). There are numerous knowledge gaps in the epidemiology of MRSA in these populations that limit understanding of its ecology in urban environments. For example, fecal shedding of MRSA, which may increase environmental contamination, has been reported in other species; however, it is unknown whether Norway rats carry the bacteria rectally. Furthermore, while intermittent MRSA shedding has been shown in other species and may dictate when the risk of transmission is highest, duration of carriage has not been examined for Norway rats. Previous work has shown that lethal animal-control methods may increase the level of pathogens within reservoir populations, possibly by disrupting ecological patterns. However, the impact of rodent-control on potentially environmentally acquired pathogens like MRSA has not been tested. Using capture-mark-recapture methods in an inner-city neighborhood in Vancouver, Canada, we show that rats intermittently carry MRSA both in the rectum and oropharynx. By assessing the prevalence of MRSA before and after enacting a pest-control intervention, we report that kill-trapping had no impact on the prevalence of carriage of this environmentally-acquired agent.

Leptospira spp. in the Oral Cavity of Urban Brown Rats ( Rattus norvegicus) from Vancouver, Canada-Implications for Rat-Rat and Rat-Human Transmission.

We tested the urine and saliva of 137 wild rats ( Rattus norvegicus) from Vancouver, Canada, for the presence of Leptospira spp. Only one saliva sample was found positive and two were suspect, all from urine-positive rats ( n=81), indicating that active shedding of leptospires in saliva is unlikely to occur.

Effects of Culling on Leptospira interrogans Carriage by Rats.

We found that lethal, urban rat control is associated with a significant increase in the odds that surviving rats carry Leptospira interrogans. Our results suggest that human interventions have the potential to affect and even increase the prevalence of zoonotic pathogens within rat populations.