Urban rats are commensal pests that thrive in cities by exploiting the resources accompanying large human populations. Identifying long-term trends in rat numbers and how they are shaped by environmental changes is critical for understanding their ecology, and projecting future vulnerabilities and mitigation needs. Here, we use public complaint and inspection data from 16 cities around the world to estimate trends in rat populations. Eleven of 16 cities (69%) had significant increasing trends in rat numbers, including Washington D.C., New York, and Amsterdam. Just three cities experienced declines. Cities experiencing greater temperature increases over time saw larger increases in rats. Cities with more dense human populations and more urbanization also saw larger increases in rats. Warming temperatures and more people living in cities may be expanding the seasonal activity periods and food availability for urban rats. Cities will have to integrate the biological impacts of these variables into future management strategies.

While literature indicates that municipal rat management approaches are often unsuccessful, a lack of research comparing strategies makes the breadth of opportunities and challenges associated with different approaches uncertain. Here, we explored the municipal rat management policies and programs in seven cities in the United States of America. Rat policies were attained by collecting rat management-related municipal codes in each city. Information on rat programs was obtained through interviewing program stakeholders. Analysis followed a qualitative framework method to identify and describe themes associated with the structure and function of management approaches. Municipal codes served as a foundation for municipalities by outlining when, where, how, and by whom rat problems should be addressed. Programs employed the primary people responsible for performing on-the-ground management and they acted as a municipal "brain," organizing the city's strategy. We identify opportunities and barriers for other municipalities to consider in the design of their own rat management strategies.

To sustainably control urban rat infestations, management efforts need to encompass large areas of urban centers. Therefore, the objective of this review and narrative synthesis was to collate what is known about municipal-scale rat management. We explored the management frameworks that have been used at a large scale in cities and we describe the expectations of experts who have designed and implemented these frameworks. We found that there has been a persistent “war on rats” paradigm driving this literature since the early 1900s. Not only was there little quantitative evidence to support this paradigm and associated methodologies, but together, they failed to meet the expectations of those who designed and implemented them due to real-world constraints (i.e., limited resources). To improve the field of municipal management, we identify two distinct options. First, stakeholders may continue to wage the “war on rats” while improving existing strategies within this paradigm. Key pathways forward include developing evaluation metrics aligned with program objectives, establishing the cost-effectiveness of methodologies, and improving control efficacy. Second, we suggest a new paradigm, one that considers that rat management is a complex system that must be approached by first mapping its complexity to highlight and prioritize the many complex upstream determinants of infestations. This perspective highlights how rat management may be a wicked problem for which there is no overarching solution and instead can only be managed by making incremental gains in individual components of the problem over time. Importantly, we propose an alternative management objective that places a priority on improving the overall health of the community, instead of on eliminating rats, and we stress that management goals must address stakeholders’ goals as their investment is essential for a sustained program.

The house mouse, Mus musculus domesticus, creates significant public health risks for residents in low-income multi-family dwellings (MFDs). This study was designed to evaluate the spatial distribution of house mice in MFDs. Four low-income high-rise apartment buildings in three cities in New Jersey were selected for building-wide monitoring on two occasions with approximately one year between the monitoring events. The presence of a house mouse infestation was determined by placing mouse bait stations with three different non-toxic baits for a one-week period in all accessible units as well as common areas. Permutation tests were conducted to evaluate house mouse infestation spatial patterns. All four analyzed buildings exhibited a significant correlation between apartments with house mouse infestations and whether they share a common wall or ceiling/floor at both sampling periods except one building during the second inspection, which contained a high number of isolated apartments. Foraging ranges, speed of locomotion, and dispersal behavior of house mice are relatively larger, faster, and more common, respectively, compared to common urban arthropod pests. This could lead to the conclusion that house mice are as likely to infest non-neighboring apartments as those that share a wall or floor/ceiling. However, these results demonstrate that house mouse infestations tend to occur among apartments that share common walls or ceilings/floors. This spatial distribution pattern can be utilized in rodent management plans to improve the efficiency of house mouse management programs in MFDs.

Rodent management programs at food distribution centers in the United States and Canada often adhere to interval-based spacing of control devices, with traps spaced 6-12 m apart on the interior perimeter, and exterior bait stations spaced 15-30 m apart. However, this design is based only on rodent foraging ranges, and does not consider the influence of rodent behavior or biology on movement patterns. Therefore, this study evaluated characteristics of food distribution centers that influence rodent behavior to determine their impact on interior trap capture and exterior bait feeding by rodents. We found that rodent interactions with control devices was not uniform in facilities, and less than half (45.2%) of all interior devices trapped at least one mouse. Rodent feeding at exterior bait stations was similarly not uniform, with 56.1% of observations representing minor feeding (one corner of bait or less consumed). Furthermore, we found that certain ecological and structural characteristics of device location were associated with higher trap capture and/or bait consumption. Results of this investigation suggest that rodent management at food distribution centers can be improved with assessment-based placement of traps and bait stations. In addition to reducing food safety threats through improved trap capture, this approach can reduce the number of devices to service and redirect service time toward pro-active inspections, rather than trap checking. Finally, device locations that are assessment-based align with the 2011 Food Safety Modernization Act that mandates preventive controls to protect human food.

Abstract Rats contaminate foods and spread pathogens. Thus, changes in rat populations have consequences for society, especially in densely-populated cities. Following widespread social distancing and lockdown measures to curtail SARS-CoV-2, worldwide media outlets reported increased sightings of rats. To document possible changes in rat populations, we: (i) examined public service requests in the 6 years before, and during, ‘lockdown’ in New York City; (ii) used spatial analyses to identify calls in proximity to food service establishments (FSE); and (iii) surveyed pest-management companies. Over 6 years prior to the pandemic, we found a consistent moderate spatial association (r = 0.35) between FSE and rat-related calls. During the early stages of the pandemic, the association between rat reports and food services did not decrease as would be expected by restaurant closures, but instead modestly increased (r = 0.45). There was a 29.5% decrease in rat reports, overall. However, hotspot analysis showed that new reports were highly localized, yet absent in several industrial areas they were previously observed in, potentially masking a higher proportion of calls in neighborhoods near closed restaurants. Additionally, 37% of pest management companies surveyed reported that, unlike previous years, 50–100% of requests were from new clients and addresses. The finding that hotspots remained nearby dense clusters of restaurants does not support the common narrative that rats moved long distances. Rather, our results are consistent with rats finding nearby alternative food resources. Tracking these dynamics as the COVID-19 pandemic abates will be an important step to identifying how rats respond to society returning to normal activity patterns.

The house mouse, Mus musculus domesticus, is a common pest in multi-family residential apartment buildings. This study was designed to gain insights into residents’ impressions of house mice, develop more effective house mouse detection methods, and evaluate the effectiveness of building-wide house mouse management programs. Two high-rise apartment buildings in New Jersey were selected for this study during 2019–2020. Bait stations with three different non-toxic baits were used to detect house mouse activity. Two rodenticides (FirstStrike®—0.0025% difethialone and Contrac®—0.005% bromadiolone) were applied by researchers over a 63-day period and pest control operations were then returned to pest control contractors for rodent management. There were significant differences in the consumption rates of non-toxic baits and two toxic baits tested. A novel non-toxic bait, chocolate spread, was much more sensitive than the two commercial non-toxic baits for detecting mouse activity. The house mouse management programs resulted in an average 87% reduction in the number of infested apartments after three months. At 12 months, the number of infestations decreased by 94% in one building, but increased by 26% in the second building. Sustainable control of house mouse infestations requires the use of effective monitoring strategies and control programs coupled with preventative measures.

Following widespread closures of food-related businesses due to efforts to curtail the spread of SARS-CoV-2, public health authorities reported increased sightings of rats in close vicinity of people. Because rats vector a number of pathogens transmissible to people, changes in their behavior has consequences for human health risks. To determine the extent of how stay-at-home measures influenced patterns of rat sightings we: 1) examined the number of rat-related public service requests before and during the period of lockdown in New York City (NYC) and Tokyo, Japan; 2) examined reports made in proximity to closed food service establishments in NYC; and 3) surveyed pest control companies in the United States, Canada, Japan, and Poland. During the month following lockdown, the overall number of reports decreased by 30% in NYC, while increasing 24% in Tokyo. However, new hotspots of 311 calls were observed in proximity of closed food service establishments in NYC; and there was a consistent positive association between kernel density estimates of food service establishments and location of 311 calls ( r = 0.33 to 0.45). Similarly, more reports were observed in the restaurant-dense eastern side of Tokyo. Changes in clientele for pest control companies varied geographically, with 37% of pest-management companies surveyed in North America reporting 50-100% of their post-lockdown rat-related requests coming from new clients. In Warsaw, where there are no clusters of restaurants in densely-populated areas, there were no changes. In Tokyo, there were no changes in clients. We conclude that changes in public service calls are region-specific and localized, with increases in rat sightings more likely near restaurant-dense regions. Pest control companies surveyed in North America either lost much of their business or shifted clientele from old to new locations. We discuss possible mitigation measures including ramping up pest control during re-opening of food-related establishments and the need for citywide rodent surveillance and disease monitoring.

Recent advances in high-throughput sequencing technology have led to a rapid expansion in the number of viral sequences associated with samples from vertebrates, invertebrates and environmental samples. Accurate host identification can be difficult in assays of complex samples that contain more than one potential host. Using unbiased metagenomic sequencing, we investigated wild house mice (Mus musculus) and brown rats (Rattus norvegicus) from New York City to determine the aetiology of liver disease. Light microscopy was used to characterize liver disease, and fluorescent microscopy with in situ hybridization was employed to identify viral cell tropism. Sequences representing two novel negative-sense RNA viruses were identified in homogenates of wild house mouse liver tissue: Amsterdam virus and Fulton virus. In situ hybridization localized viral RNA to Capillaria hepatica, a parasitic nematode that had infected the mouse liver. RNA from either virus was found within nematode adults and unembryonated eggs. Expanded PCR screening identified brown rats as a second rodent host for C. hepatica as well as both nematode-associated viruses. Our findings indicate that the current diversity of nematode-associated viruses may be underappreciated and that anatomical imaging offers an alternative to computational host assignment approaches.

The microbiome of wild Mus musculus (house mouse), a globally distributed invasive pest that resides in close contact with humans in urban centers, is largely unexplored. Here, we report analysis of the fecal virome of house mice in residential buildings in New York City, NY. Mice were collected at seven sites in Manhattan, Queens, Brooklyn, and the Bronx over a period of 1 year. Unbiased highthroughput sequencing of feces revealed 36 viruses from 18 families and 21 genera, including at least 6 novel viruses and 3 novel genera. A representative screen of 15 viruses by PCR confirmed the presence of 13 of these viruses in liver. We identified an uneven distribution of diversity, with several viruses being associated with specific locations. Higher mouse weight was associated with an increase in the number of viruses detected per mouse, after adjusting for site, sex, and length. We found neither genetic footprints to known human viral pathogens nor antibodies to lymphocytic choriomeningitis virus. IMPORTANCE Mice carry a wide range of infectious agents with zoonotic potential. Their proximity to humans in the built environment is therefore a concern for public health. Laboratory mice are also the most common experimental model for investigating the pathobiology of infectious diseases. In this survey of mice trapped in multiple locations within New York City over a period of 1 year, we found a diverse collection of viruses that includes some previously not associated with house mice and others that appear to be novel. Although we found no known human pathogens, our findings provide insights into viral ecology and may yield models that have utility for clinical microbiology.

ABSTRACT House mice (Mus musculus) thrive in large urban centers worldwide. Nonetheless, little is known about the role that they may play in contributing to environmental contamination with potentially pathogenic bacteria. Here, we describe the fecal microbiome of house mice with emphasis on detection of pathogenic bacteria and antimicrobial resistance genes by molecular methods. Four hundred sixteen mice were collected from predominantly residential buildings in seven sites across New York City over a period of 13 months. 16S rRNA sequencing identified Bacteroidetes as dominant and revealed high levels of Proteobacteria. A targeted PCR screen of 11 bacteria, as indicated by 16S rRNA analyses, found that mice are carriers of several gastrointestinal disease-causing agents, including Shigella, Salmonella, Clostridium difficile, and diarrheagenic Escherichia coli. Furthermore, genes mediating antimicrobial resistance to fluoroquinolones (qnrB) and β-lactam drugs (blaSHV and blaACT/MIR) were widely distributed. Culture and molecular strain typing of C. difficile revealed that mice harbor ribotypes associated with human disease, and screening of kidney samples demonstrated genetic evidence of pathogenic Leptospira species. In concert, these findings support the need for further research into the role of house mice as potential reservoirs for human pathogens and antimicrobial resistance in the built environment. IMPORTANCE Mice are commensal pests often found in close proximity to humans, especially in urban centers. We surveyed mice from seven sites across New York City and found multiple pathogenic bacteria associated with febrile and gastrointestinal disease as well as an array of antimicrobial resistance genes.

Given the history of well-documented rodent infestations in New York City we were interested in assessing the economic impact of rats and mice on small businesses in The Lower East Side of Manhattan. Via mailed surveys and on-site interviews , we quantified damage to structures, loss of saleable goods and merchandise, the cost of pest-control professionals, and/or self-applied poison/traps. Overall, 16% of business (n = 76) responded to our queries. To those businesses reporting some level of rodent damage, average losses included $513 in merchandise, $726 in pest-control fees, $371 in repair costs to structure, and $125 in do-it-yourself deployment of poison and traps. Average annual loss to those business owners that reported rodent infestations was estimated at $1104. Our observations suggest that commensal rodents in New York City have remained persistent pests that are capable of inflicting noteowrthy economic losses. Given the significant effort by the City of New York in the fight against rodent infestations we suggest that persistent environmental degradation and possibly even genetic resistance to 2nd generation rodenticides have enabled city rodents to persist and flourish despite the various campaigns to thwart them.