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Rats! The Regions With the Most Sightings

Several cities have intensified their efforts to combat rat infestations. It’s no simple task.

Rats, it seems, are running rampant in the nation's capital. Thanks in part to a mild winter, requests for rodent abatement in Washington, D.C., jumped more than 50 percent last year. City officials recently responded by unveiling a large-scale initiative that aims to contain the growing rat population by strategically deploying rat-proof trash cans in problem areas and conducting outreach to property owners, among other things.

Local governments in the same boat are also stepping up efforts to combat rat infestations. Earlier this month, New York City Mayor Bill de Blasio announced a $32 million investment targeting the city’s three most rat-infested areas. Chicago and other jurisdictions are experimenting with a new dry ice pest extermination product that experts say holds promise in the war on rats.

Rodents aren’t just a nuisance; they're a public health problem. Leptospirosis, a bacterial infection that most often spreads via rat urine, was blamed earlier this year for killing one Bronx resident and infecting two others. Reported cases directly linking illnesses or deaths to rats are extremely rare, though. Rodents are also responsible for property damage, wreaking havoc on car engines or chewing on wires inside homes, potentially sparking electrical fires. 

A little-known dataset in the Census Bureau’s American Housing Survey provides clues as to where rodent problems are most severe, with the latest survey finding about 11 percent of U.S. households reported seeing signs of rats or mice within the past year. 

The issue is particularly bad in the Northeast and mid-Atlantic. "The corridor from Boston to Washington, D.C., has some of the rattiest cities in the world," says urban rodentologist Robert Corrigan.

Indeed, just under 18 percent of Philadelphia-area households reported rodent sightings -- the highest share of the 25 metro areas included in the Census survey. Boston (16.9 percent), New York (15.3 percent) and Washington, D.C., (13.1 percent) metro areas also reported higher rates. By contrast, less than 5 percent of households in four Sun Belt regions saw signs of rodents in their homes.

A number of factors explain why mice and rats are far more common in Northern urban areas. For one, these places tend to be much more densely populated, so rodents have an easier time finding food sources. For another, old infrastructure found in places like Boston or New York make for ideal habitats. Rodents thrive, Corrigan says, in outdated sewer systems, subways, parks and in the foundations of old homes or apartment buildings.

Although some cities are reporting recent increases in rat sightings, problems have plagued these same places for more than a century. “These old cities have had entrenched rat populations since colonial times,” says Jim Fredericks, chief entomologist at the National Pest Management Association.


If cities want to make headway in stemming rat infestations, Fredericks says, they’ll need a comprehensive approach that spans multiple city departments. The National Association of County and City Health Officials (NACCHO) reviewed local rodent control programs across the country in 2015 and found that successful programs collaborated with other city departments or outside organizations. These programs also incorporated a public outreach component.

Fluctuations in funding, however, limited rodent programs' ability to sustain positive gains over the long term. A lack of training opportunities further presented a “continual challenge," the NACCHO report noted.

Gerard Brown, who manages D.C.’s rodent control program, says there's no magic bullet. Fixing the problem, he says, requires a comprehensive approach that includes improving human behaviors and sanitation, among other components. The District's Department of Small and Local Business Development launched a grant program that provides rodent-proof commercial waste compactors in rat hotspots. Additionally, public works crews will receive real-time data from 400 new smart litter bins alerting them when they're full and need to be picked up.

The single most effective deterrent, report officials like D.C.'s Brown, is simply getting people to properly dispose of their trash. New York City, for instance, is set to explore potential legislation requiring trash to be placed out shortly before pickup.

In addition, New York has greatly expanded its “rat reservoir” program targeting areas of the city particularly prone to rats. Case managers canvas neighborhoods and work with property owners and building managers to resolve underlying conditions contributing to rat infestations. They monitor inspection and compliance, and provide training or technical assistance if needed. Eleven areas of the city are expected to "graduate" from the program after recording drops in rat activity between 60 and 90 percent, reports the city's Department of Health and Mental Hygiene.

“We think of it as a neighborhood intervention,” says Corinne Schiff, deputy commissioner for environmental health. “Rats don’t share the boundaries we have, and it takes everyone working together to control rats in a neighborhood.”

It’s worth noting the Census data covers entire metro areas rather than individual cities, and vast differences in the severity of the issue exist within certain neighborhoods. Schiff says the situation tends to be worse around business districts and areas near parks, or pretty much any place near plenty of food and water. 

Research from the State University of New York reported Census tracts with high concentrations of rat sightings were associated with older housing, vacant units, low educations levels and close proximity to subways and parks. Another Johns Hopkins Bloomberg School of Public Health study highlighted problems exacerbated by rats in poorer neighborhoods, reporting about half of residents in Baltimore’s low-income neighborhoods reported seeing rats on at least a weekly basis on their block.

Some nonprofits have promoted feral cats as a way to control rodent populations in cities such as Chicago, Portland and Washington, D.C. But no published research demonstrates they’re actually effective. Corrigan says feral cats pose their own public health problems, and they’re not likely to take on fully grown rats.

Instead, Corrigan recommends cities take a scientific approach to combating rat problems. This might include, for instance, analyzing 311 calls and other data to identify specific sewers or parks serving as breeding grounds. “The key to this is to have a scientific coalition in the cities to address these problems,” he says. 

Cities could soon add two new products to their arsenal. Chicago, D.C., and others have tested a product that works by scooping dry ice into rat burrows and then covering the holes to suffocate the rats. Experts say it’s a more humane way of killing rodents and, unlike other products, doesn’t risk poisoning birds or other animals.

Companies are also experimenting with traps and bait boxes equipped with remote sensors, alerting health inspectors or property owners when they’re breached. Corrigan says initial field trials yielded promising results and he expects cities to initiate pilot programs later this year. Knowing the exact time and location of where rats are congregating would yield better data than the often-unreliable 311 call logs cities typically rely on.

Corrigan, who works as a consultant with several local governments, views both the dry ice and sensor devices as major breakthroughs that should help cities push back against their rodent populations. But ultimately, a change in human behaviors is what's most needed if cities are to make substantial lasting progress. “The city government is only one tiny piece of controlling rats in a city,” he says. “Controlling rats is every person’s responsibility.”


About the Data

Presented data are calculated figures from the Census Bureau’s 2015 American Housing Survey. Respondents were asked whether they saw any rats or mice or signs of their presence inside homes during the previous 12 months. The Census methodology utilizes a sample for each area representative of numbers of renter, owner-occupied, trailer, vacant and other types of units. The survey, conducted once every two years, includes the 15 largest metro areas and a rotating group of 10 other selected regions.

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