New York City public health team develops indicators for predicting rat infestations

A team of researchers from the New York City Department of Health has developed ways of predicting rat infestations based on the type of neighborhood that people live in.

TV and movies have frequently shown rats in neighborhoods with squalid conditions, in areas near restaurants and near apartment buildings in poor neighborhoods. But these portrayals are based on human perceptions and associations between poverty and pest populations. However, few studies have set out to define factors that could predict where rat infestations would be.

Some studies have used reports of rat bites to locate infestations, but predicting future infestations based on property location and homeowner wealth has not been examined. In addition, the NYC study included the factor of business improvement districts, or BIDs, to see if they made a difference in rat infestations.

To develop the predictive model, the scientists studied the presence of current infestations in neighborhoods. Rats were considered present if the scientists could find any of the following signs: fresh tracks, fresh droppings, active burrows, active runways and rubmarks, fresh gnawing marks and of course live rats.

The scientists examined housing location factors such as distance to and density of restaurants and schools, brick catch basins, subways and rail lines, and open space. In addition, the looked at building materials, poverty level and location within a business improvement district.

Within the Bronx and Manhattan, researchers found that 8.2 percent of properties were “rat active.” The highest percentage of rat signs was in open land. Of the properties that contained buildings, rat active properties tended to be:

  • Larger with more residential units
  • Multifamily dwellings
  • Properties with more than 10 residential units
  • 60 percent larger in square footage than properties without rats
  • Publicly owned

Neighborhoods showing signs of rat activity tended to be:

  • Within 100 feet of a rail or subway station, or a school
  • Close to a brick catch basin or open space
  • In high poverty neighborhoods

Researchers found that neighborhoods in business improvement districts tended to have fewer signs of infestations. The authors surmise that this could be because BIDs typically fund street cleaning, litter pick-up, replacement and maintenance of trash cans, and other sanitary measures.

In general, the researchers discovered that properties that were inhabited and maintained, as long as they were not near a school, restaurant or rail station, tended to have fewer signs of rat activity. Wealthy neighborhoods tended to have the least rat activity, no matter where they were. Although this finding is not surprising, the research did reveal that BIDs can have a positive effect on the conditions of a neighborhood.

The authors suggest that city planners may want to expand BIDs in poorer neighborhoods or establish programs that increase garbage pickup frequency, improve street cleanliness and improve garbage maintenance.

Source: Sarah Johnson, Bragdon, C., Olson, C. Merlino, M., and Bonaparte, S. (2016). Characteristics of the built environment and the presence of the Norway rat in New York City: Results from a neighborhood rat surveillance program, 2008-2010. Environmental Health. 78 (10): 22-29.

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