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Background The presence of urban rats in the neighbourhood environment may negatively impact the physical and mental health of residents. Our study sought to describe the experiences with, perceptions of, and feelings towards rats and rat control efforts among a group of disadvantaged urban residents in Vancouver, Canada. Methods Semi-structured interviews were held with 20 members of the Vancouver Area Network of Drug Users (VANDU) recruited by VANDU staff. Interviews were audio recorded, transcribed, and analyzed using thematic analysis. Results Participants reported daily sightings of rats and close contact during encounters. Participants generally disliked encountering rats, raising issues of health and safety for themselves and the community due to the belief that rats carry disease. Fear of rats was common, and in some cases resulted in avoidance of rats. Effects of rats on participants were particularly pronounced for those living with rats in the home or for homeless participants who described impacts on sleep due to the sounds made by rats. Although rats were viewed as more problematic in their neighbourhood than elsewhere in Vancouver, participants believed there to be a lack of neighbourhood-level control initiatives that angered and disheartened participants. In combination with other community-level concerns (e.g., housing quality and availability), the presence of rats was viewed by some to align with a general disregard for the community and its residents. Conclusions This study suggests that the presence of rats in urban centres may have several consequences on the physical and mental health of residents living in close contact with them. These effects may be exacerbated with continued contact with rats and when residents perceive a lack of initiative to control rats in their neighbourhood. As such, research and policies aimed at mitigating the health risks posed by rats should extend beyond disease-related risk and incorporate diverse health outcomes.

Rats are an important issue in cities globally. Despite their ubiquity, perceptions and concerns about rats vary with circumstance and the context in which a person interacts with them. Municipal rat management programs are a service to communities and therefore must be responsive to the varied concerns of their residents. Understanding why communities are concerned about rats can help inform rat management programs to meet the specific needs of their residents. The objective of this study was to identify why the residents of Vancouver, Canada care about rats and what they want done to address them. To do this, we qualitatively analyzed 6,158 resident complaints about rats made to the city’s municipal government between January 2014 and May 2020. Using a qualitative descriptive coding process, we found that rats were a priority in a minority of cases. In general, people were more concerned about broader community issues, such as neighborhood disorder, of which rats were one part. Complaints tended to be made when problems were highly visible, nearby, and when the complainant wanted the city to take action to alleviate this issue, particularly when they were in and around their living spaces. The rates of complaints were highest in the most economically and socially deprived neighborhoods and lowest in the most privileged neighbourhoods. We synthesize this information with a view towards understanding how to develop objectives and actions for municipal management strategies that are grounded in community concerns.

Norway and black rats (Rattus norvegicus and Rattus rattus) are among the most ubiquitous urban wildlife species and are the source of a number of zoonotic diseases responsible for significant human morbidity and mortality in cities around the world. Rodent ecology is a primary determinant of the dynamics of zoonotic pathogens in rodent populations and the risk of pathogen transmission to people, yet many studies of rat-associated zoonoses do not account for the ecological characteristics of urban rat populations. This hinders the development of an in-depth understanding of the ecology of rat-associated zoonoses, limits comparability among studies, and can lead to erroneous conclusions. We conducted a year-long trapping-removal study to describe the ecological characteristics of urban rat populations in an inner-city neighborhood of Vancouver, Canada. The study focused on factors that might influence the ecology of zoonotic pathogens in these populations and/or our understanding of that ecology. We found that rat population density varied remarkably over short geographical distances, which could explain observed spatial distributions of rat-associated zoonoses and have implications for sampling and data analysis during research and surveillance. Season appeared to influence rat population composition even within the urban environment, which could cause temporal variation in pathogen prevalence. Body mass and bite wounds, which are often used in epidemiologic analyses as simple proxies for age and aggression, were shown to be more complex than previously thought. Finally, we found that factors associated with trapping can determine the size and composition of sampled rat population, and thus influence inferences made about the source population. These findings may help guide future studies of rats and rat-associated zoonoses.

Native to China and Mongolia, the brown rat (Rattus norvegicus) now enjoys a worldwide distribution. While black rats and the house mouse tracked the regional development of human agricultural settlements, brown rats did not appear in Europe until the 1500s, suggesting their range expansion was a response to relatively recent increases in global trade. We inferred the global phylogeography of brown rats using 32 k SNPs, and detected 13 evolutionary clusters within five expansion routes. One cluster arose following a southward expansion into Southeast Asia. Three additional clusters arose from two independent eastward expansions: one expansion from Russia to the Aleutian Archipelago, and a second to western North America. Westward expansion resulted in the colonization of Europe from which subsequent rapid colonization of Africa, the Americas and Australasia occurred, and multiple evolutionary clusters were detected. An astonishing degree of fine-grained clustering between and within sampling sites underscored the extent to which urban heterogeneity shaped genetic structure of commensal rodents. Surprisingly, few individuals were recent migrants, suggesting that recruitment into established populations is limited. Understanding the global population structure of R. norvegicus offers novel perspectives on the forces driving the spread of zoonotic disease, and aids in development of rat eradication programmes.

Urbanization often substantially influences animal movement and gene flow. However, few studies to date have examined gene flow of the same species across multiple cities. In this study, we examine brown rats ( Rattus norvegicus ) to test hypotheses about the repeatability of neutral evolution across four cities: Salvador, Brazil; New Orleans, USA; Vancouver, Canada; and New York City, USA. At least 150 rats were sampled from each city and genotyped for a minimum of 15 000 genome-wide single nucleotide polymorphisms. Levels of genome-wide diversity were similar across cities, but varied across neighbourhoods within cities. All four populations exhibited high spatial autocorrelation at the shortest distance classes (less than 500 m) owing to limited dispersal. Coancestry and evolutionary clustering analyses identified genetic discontinuities within each city that coincided with a resource desert in New York City, major waterways in New Orleans, and roads in Salvador and Vancouver. Such replicated studies are crucial to assessing the generality of predictions from urban evolution, and have practical applications for pest management and public health. Future studies should include a range of global cities in different biomes, incorporate multiple species, and examine the impact of specific characteristics of the built environment and human socioeconomics on gene flow.

Norway rats (Rattus norvegicus) and black rats (Rattus rattus) are among the most prolific and widespread urban pest species in the world. Yet despite their ubiquity, a unified understanding of the ecology of these species in urban habitats eludes us. A comprehensive understanding of urban rat ecology is important for managing rat populations and mitigating the harmful effects that they may have on urban ecosystems (e.g., structural damage, food contamination, and disease spread). The objective of this systematic review and narrative synthesis is to collate, compare, and contrast data from the published literature regarding the ecology of Norway and black rats in urban centers. Themes emerging from the synthesis process, and discussed in detail, include population dynamics, behavior, movement, and environmental influences on rat populations.

We tested liver samples from 372 Norway rats (Rattus norvegicus) from southern Ontario, Canada, during 2018–2021 to investigate presence of hepatitis E virus infection. Overall, 21 (5.6%) rats tested positive for the virus. Sequence analysis demonstrated all infections to be rat hepatitis E virus (Rocahepevirus ratti genotype C1).

Leptospira interrogans is a bacterial zoonosis with a worldwide distribution for which rats (Rattus spp.) are the primary reservoir in urban settings. In order to assess, monitor, and mitigate the risk to humans, it is important to understand the ecology of this pathogen in rats. The objective of this study was to characterize the ecology of L. interrogans in Norway rats (Rattus norvegicus) in an impoverished inner-city neighborhood of Vancouver, Canada. Trapping was performed in 43 city blocks, and one location within the adjacent port, over a 12 month period. Kidney samples were tested for the presence of L. interrogans using PCR and sequencing. A multivariable model was built to predict L. interrogans infection status in individual rats using season and morphometric data (e.g., weight, sex, maturity, condition, etc.) as independent variables. Spatial analysis was undertaken to identify clusters of high and low L. interrogans prevalence. The prevalence of L. interrogans varied remarkably among blocks (0-66.7%), and spatial clusters of both high and low L. interrogans prevalence were identified. In the final cluster-controlled model, characteristics associated with L. interrogans-infection in rats included weight (OR = 1.14, 95% CI = 1.07-1.20), increased internal fat (OR = 2.12, 95% CI = 1.06-4.25), and number of bite wounds (OR = 1.20, 95% CI = 0.96-1.49). Because L. interrogans prevalence varied with weight, body fat, and bite wounds, this study suggests that social structure and interactions among rats may influence transmission. The prevalence and distribution of L. interrogans in rats was also highly variable even over a short geographic distance. These factors should be considered in future risk management efforts.

Urban Norway rats ( Rattus norvegicus ) can carry various human pathogens, and may be involved in pathogen propagation and transmission to humans. From January 31–August 14, 2021, a community outbreak of Shigella flexneri serotype 2a occurred among unhoused or poorly housed people in the Downtown Eastside neighborhood of Vancouver, British Columbia, Canada. The source could not be identified; however, patients reported contact with rats, and previous studies indicated transmission of rat-associated zoonotic pathogens among the unhoused or poorly housed residents of this neighborhood. The study objective was to determine if rats trapped in the outbreak area were carriers of Shigella spp. and other zoonotic enteric pathogens. From March 23–April 9, 2021, 22 rats were lethally trapped within the outbreak area. Colonic content was analyzed using the BioFire FilmArray Gastrointestinal (multiplex PCR) panel for human enteropathogens, which detected: Campylobacter spp. (9/22), Clostridioides difficile (3/22), Yersinia enterocolitica (5/22), Cryptosporidium spp. (8/22), Giardia duodenalis (5/22), Rotavirus A (1/22), enteroaggressive Escherichia coli (2/22), enteropathogenic E . coli (10/22), and Shigella spp. or enteroinvasive E . coli (EIEC) (3/22). An ipaH PCR assay was used for targeted detection of Shigella spp./EIEC, with five rats positive. Two samples contained insertion sites unique to S . flexneri isolated from the human outbreak. This study highlights the potential for rats to carry a broad range of human pathogens, and their possible role in pathogen maintenance and/or transmission.

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of multi-drug-resistant infections in people, particularly indigent populations. MRSA can be transmitted between people and domestic animals, but the potential for transmission between people and commensal pests, particularly rodents, had not been investigated. The objective of this study was to identify the presence and characterize the ecology of MRSA in rats (Rattus spp.) from in an impoverished, inner-city neighborhood. Oropharyngeal swabs were collected from rats trapped in 33 city blocks and one location within the adjacent port. Bacterial culture was performed and MRSA isolates were characterized using a variety of methods, including whole-genome sequencing (WGS). The ecology of MRSA in rats was described using phylogenetic analysis, geospatial analysis, and generalized linear mixed models. MRSA was identified 22 of 637 (3.5%) rats tested, although prevalence varied from 0 - 50% among blocks. Isolates belonged to 4 clusters according to WGS, with the largest cluster (n = 10) containing isolates that were genetically indistinguishable from community-acquired USA300 MRSA strains isolated from people within the study area. MRSA strains demonstrated both geographic clustering and dispersion. The odds of an individual rat carrying MRSA increased with increased body fat (OR = 2.53, 95% CI = 1.33-4.82), and in the winter (OR = 5.29, 95% CI = 1.04-26.85) and spring (OR = 5.50, 95% CI = 1.10-27.58) compared to the fall. The results show that urban rats carried the same MRSA lineages occurring in local human and/or animal populations, supporting recent transmission from external sources. MRSA carriage was influenced by season, most likely as a result of temporal variation in rat behavior and rat-human interactions.