September 26, 2012 Celeste Monforton, DrPH, MPH 0Comment

Mayor Rudolph Guiliani called them “horrible” and “frightening” (NYTimes July 11, 2000.)  The current Mayor, Michael Bloomberg, said they are “repulsive” and announced in 2003 that his administration had “zero tolerance” for them (NYTimes, Aug 15, 2003.)   I’m sure their predecessors used equally harsh language to describe New York City’s unwelcome inhabitants: rattus norvegicus, a.k.a., the Norway rat.  I’m also confident that there have been dozens and dozens of campaigns over the decades to rid their fine city of the rodents.


The trouble is, rattus norvegicus is not too fussy about its environment.  His (and her) needs are pretty simple: food, water and shelter, and none of them have to be gourmet, or posh, or luxury.  A neighborhood needs everyone working to make the environment inhospitable for rattus norvegicus, but that’s easier said than done.  Washington, DC has its Rat Free DC program, with a scary warning “Know Your Enemy.”  Philadelphia’s Vector Control Office’s “How to Keep Rats Out!” program uses the slogan “Starve the out!  Build them out!! Knock them out!!!” But cities’ rat response teams will tell you that catchy mottos, rodent baiting and blitzes are temporary fixes.  That’s why New York City tried something different.

Last week’s Morbidity and Mortality Weekly Report (MMWR) featured a report by the City of New York’s Department of Health and Mental Hygiene on its Neighborhood Rat-Management Program.  For nearly two years beginning in December 2007, the City’s Division of Environmental Health conducted active surveillance in 11 Bronx neighborhoods consisting of about 36,000 privately owned properties and more than 770,000 residents.  The areas were known for chronic rat infestations and a major demolition project nearby was expected to displace another large horde of the rodents.  The program coordinator and staff collaborated with community leaders to generate support for the effort and recruited building owners and managers to attend a three-day training program called the “Rodent Academy.”  Organizers warn the curriculum is not a “sit back and listen seminar.”  Among other things, students asked to bring their flashlights for the field work.

The surveillance program (or “rat indexing”) was conducted by inspectors with the City’s Division of Environmental Health and occurred in three rounds.  The inspectors walked every block of the surveillance area and used handheld computers to record and rank these six different active rat signs (ARS):

  1. Fresh tracks
  2. Fresh droppings
  3. Active burrows
  4. Active runways and rub marks
  5. Fresh gnawing marks
  6. Live rats

The inspectors assigned severity scores for each observed ARS, and also noted the presence of open food waste, clutter or other conditions friendly to rats.  Ultimately, the indexing data was publicly available on what the authors called a “rat information portal.”  But they just weren’t collecting data.   When inspectors observed ARS or conditions favorable to rattus norvegicus, the property owner was promptly sent a notice detailing the findings and ways to correct the problem.  Owners were given about a week to make corrections and failure to do so resulted in a compliance inspection.  Property owners who failed to comply with the Health Department’s order received a citation, and were charged for the city’s cost of cleaning up the conditions and applying rodenticide bait.

With the baseline indexing data (round 1) of 35,691 properties, the participating communities and the program staff were able to monitor the impact of the program. In round 1, nearly 3,000 properties had ARS.  By round 2, that number declined to about 1,700 and in round 3 to about 1,300.  The percentage of properties with severe infestation declined by 58% from round 1 to round 3.  The authors note that the program has since been expanded to neighborhoods in Queens and Brooklyn and conclude:

“…rounds of inspections conducted in neighborhoods, combined with prompt communication with owners, publication of findings, and fines for noncompliance, reduced the prevalence and severity of rat infestations in a large area with a history of severe rat problems. Urban rat control programs should include a comprehensive survey assessing ARS and environmental conditions conducive to rats and conduct inspections by neighborhood rather than by individual property alone.”



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