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Evaluation of a Neighborhood Rat-Management Program — New York City, December 2007–August 2009

The Norway rat (Rattus norvegicus) is a pervasive urban rodent that can carry a variety of pathogens transmissible to humans, bring stress to residents of infested neighborhoods, damage property, and cause financial loss (1–4). Several areas of New York City have experienced persistent rat infestation despite a longstanding rat control program that employed property-level inspection and control measures triggered by individual citizen complaints, a common approach in urban areas (3). Recognizing the need to address conditions conducive to rat infestation at the community level, in 2007 the New York City Department of Health and Mental Hygiene launched a proactive "rat indexing" (active surveillance) program, using rapid inspections of properties in several Bronx neighborhoods with persistent rat infestation (5). The program included repeated, neighborhood-wide inspections; education and enforcement actions to promote rat control measures by property owners; and community outreach. Signs of rat infestation were noted and recorded electronically by inspectors, and records were analyzed to evaluate program effectiveness. After three rounds of indexing over a 21-month period, the percentage of properties with active rat signs (ARS) had declined 54%, and the percentage with severe rat infestation had declined 58%. The indexing approach to rat control subsequently was expanded to other parts of the city. Indexing can be an effective control strategy in urban neighborhoods with persistent rat infestation.

Within the Bronx, a zone consisting of approximately 36,000 privately owned properties was selected for the pilot rat indexing program based on 1) historically high rates of rat infestation found by complaint-based inspections, 2) support from local community boards and elected officials, and 3) expected displacement of rats by a major construction project under way in one section of the zone. The indexing zone included all or part of 11 neighborhoods, as defined by community district boundaries,* with an estimated population of 777,000 residents in 12 square miles (31 square kilometers), a density of 64,750 persons per square mile (24,775 persons per square kilometer). Approximately 37% of indexing zone residents lived below the federal poverty threshold.

During each indexing round, inspectors walked every block of each neighborhood, using handheld computers loaded with maps of the properties to record inspection findings. Inspectors were instructed to inspect as much of the exterior of the property as could be accessed at the time of inspection, including front, side, and rear yards or garbage areas, looking for any of six different ARS: 1) fresh tracks, 2) fresh droppings, 3) active burrows, 4) active runways and rub marks, 5) fresh gnawing marks, and 6) live rats (6,7). Inspectors recorded a severity score for each sign, ranging from zero (sign not present) to three; total ARS scores, including all six signs, could range from zero to 18. For this report, any property with a total ARS score ≥3 was considered to have a severe rat infestation. Inspectors also noted and recorded conditions conducive to rats including accessible "garbage" (poor containerization of food waste resulting in the feeding of rats) or "harborage" (clutter and dense vegetation promoting the nesting of rats).

An official order to abate was mailed to the owner of every private property that failed inspection, along with detailed inspection findings, a rodent control educational guide,§ and advice tailored to the problems identified by the inspection. Property owners were allowed 5–10 business days to comply with the order, after which a compliance inspection was conducted. An Internet-based rat information portal was launched in October 2008 to make rat indexing data publicly available for all properties and to promote collective responses to neighborhood-scale infestations. Agencies responsible for public properties were mailed a referral letter and expected to take action and report back in weekly rodent task force meetings. Results of both private and public property inspections were reported on the rat information portal.

When private owners failed to comply with the health department's order, inspectors issued a violation to the owner and deployed staff members licensed as pest control professionals to reinspect and, if needed, apply rodenticide bait. Certain properties with severe garbage or rat harborage conditions were cleaned by health department personnel. The costs of these services were charged to the property owner. Automated processes helped to ensure timely issuance of orders and fines, scheduling of inspections and reinspections, and tracking of progress.

Education and outreach were conducted throughout the Bronx. A coordinator met with local elected officials and community boards and built relationships with community-based organizations. A local Bronx weatherizing (sealing and insulating) company was engaged to assist in rodent prevention outreach efforts and to launch a "Rodent Academy" for building owners, managers, and superintendents.

From December 3, 2007, to August 21, 2009, three rounds of indexing were completed. In round 1, a total of 35,691 properties were indexed. Because indexing inspections were simpler and more efficient than the typical complaint-based inspections,** the six inspectors were able to index an average of 88 properties per inspector per work day, compared with an average of 10 properties per inspector per work day for typical complaint-based inspections. Accuracy of the inspections was evaluated by performing the more thorough complaint-based inspection methods on 49 properties that were randomly selected from the 35,691 properties in the indexing zone. Fourteen of the 49 properties were found to have ARS after the more thorough inspection. Of those 14 properties, 12 (86%) had been correctly identified as having ARS by the indexing program; two properties that had passed the indexing inspection failed the complaint-based inspection.

Because of changes in the indexing zone and properties lost to follow-up, 5,695 (16%) of the properties inspected in round 1 (including 1.98% found to have ARS) were not reinspected in round 2 and round 3. The remaining 29,996 (84%) properties, including 2,926 (9.75%) with ARS in round 1, comprised the study cohort for this report (Table). In round 2, the number of properties with ARS declined to 1,748 (5.83%), and in round 3, the number declined to 1,354 (4.51%). From round 1 to round 3, the number of properties with ARS declined by 1,572 or 54% (p<0.001). The percentage of properties with severe infestation (total severity score ≥3) declined 58%, from 0.48% in round 1 to 0.20% in round 3 (p<0.001).

Among the 2,926 properties with ARS in round 1, a total of 371 did not receive a compliance inspection because of various factors.†† Of the remaining 2,555 properties, a total of 1,153 (45%) failed their immediate compliance inspection. Of these, 361 (31%) still had ARS in round 2. In contrast, among the 1,402 (55%) properties with ARS in round 1 that passed their compliance inspection, only 224 (16%) still had ARS during round 2 indexing (p<0.001).

Reported by

Caroline Bragdon, MPH, Daniel Kass, MSPH, Thomas Matte, MD, Mario Merlino, MS, Sancia Bonaparte, MPH, Sarah Johnson, MS, Robert Corrigan, PhD, Div of Environmental Health, New York City Dept of Health and Mental Hygiene, New York, New York. Corresponding contributor: Caroline Bragdon, cbragdon@health.nyc.gov, 212-788-9636.

Editorial Note

This report describes how New York City found that 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 (3,5–10). Directly comparable data on properties with ARS were not collected from other New York City neighborhoods during the same period as the Bronx intervention. However, compared with the rat indexing data in the Bronx, much lower percentage declines in the number of rat sighting complaints under the complaint-based system were observed from 2007 to 2009 in Brooklyn (16%) and Queens (10%). Given the results from rat indexing in the Bronx, New York City has expanded the program to include all of Manhattan and limited neighborhoods in Queens and Brooklyn, in addition to the Bronx.

Previous large-scale rat control initiatives were conducted in the 1990s in Baltimore, Maryland, and Boston, Massachusetts. Baltimore found that a decrease in the prevalence of rat infestation could be achieved, but the results were largely attributable to a government-subsidized baiting program (8). Boston tracked sanitation deficiencies and signs of rodent activity on properties within the area of the "Big Dig" highway construction corridor and in surrounding neighborhoods in periodic surveys and achieved an 87% reduction in referrals for rat activity and sanitation violations. Boston's program also included extensive baiting services in and around the construction area and sewer lines (3,9).

New York City's rat indexing program is similar to the rat control programs in Baltimore and Boston in that a neighborhood-wide survey was used to assess a baseline prevalence of infestation (round 1) before the intervention. The New York City program differed from those of the other two cities in its focus on rapid indexing inspections and the expectation that property owners would respond to rat infestations rather than rely mainly on extensive baiting by the city government.

The findings in this report are subject to at least two limitations. First, although owners of properties with ARS were advised to inspect, clean, remove garbage and harborage, and hire a licensed pest professional, the specific remediation actions of property owners were not recorded. Second, the rat indexing program did not include assessment or treatment of rat populations in sewers, subways, or other subsurface infrastructures. Some properties might have passed inspection while harboring subsurface rats that would later emerge to forage in the indexing zone. In such cases, the reduction in ARS might have been temporary, and neighborhoods might have continued to experience infestations even if rat activity had been abated at the surrounding properties (3,9).

All municipal rat control programs recognize the importance of outreach and education to neighborhoods (3,5,8,9), but the actual impact of the New York City outreach on rat remediation is unknown. Outreach has the potential to increase knowledge of best practices in rat management, increase confidence in the community in the potential to control rats, and promote simultaneous actions that increase the likelihood of sustainable community success. Rat management at both the property and neighborhood level is best achieved through removal of food sources and harborage conditions, combined with the judicious use of rodenticides applied by trained pest professionals.

Acknowledgments

Jany Dotel, Ratha Ry, Angela Lee, Vicky Jean-Francois, Carlos Pesantes, Dave Peters, Eric Han, Juan Nieves, Edwin Arroyo, Leroy Knight, MS, Joseph Franklin, Michael Mills, Mary Freeman, John Johnston, MUP, Ricky Simeone, MS, Grant Pezeshki, MA, Oleg Gutkin, MA, Pest Control Services, New York City Department of Health and Mental Hygiene.

References

  1. Battersby S, Hirschorn RB, Amman BR. Commensal rodents. In: Bonnefoy X, Kampen H, Sweeney K, eds. Public health significance of urban pests. Geneva, Switzerland: World Health Organization; 2008:387–419.
  2. Meerburg B, Singleton G, Kijlstra A. Rodent-borne diseases and their risks for public health. Crit Rev Microbiol 2009;221–70.
  3. Colvin BA, Jackson W. Urban rodent control programs for the 21st century. Canberra, Australia: Australian Centre for International Agricultural Research; 1999:243–57.
  4. CDC. Diseases from rodents. Atlanta, GA: US Department of Health and Human Services, CDC; 2010. Available at http://www.cdc.gov/rodents. Accessed September 17, 2012.
  5. Corrigan R. A profile of the Norway rat, Rattus norvegicus. In: New York City: its impact on city operations and the need for collaborative interagency rat management programs. Timm RM, O'Brien JM, eds. Proceedings of the 22nd Vertebrate Pest Conference. Davis, California: University of California, Davis; 2006:131–41.
  6. CDC. Integrated pest management: conducting urban rodent surveys. Atlanta, GA: US Department of Health and Human Services, CDC; 2006. Available at http://www.cdc.gov/nceh/ehs/docs/ipm_manual.pdf. Accessed September 17, 2012.
  7. Davis H, Casta A, Schatz G. Urban rat surveys. Atlanta, GA: US Department of Health, Education, and Welfare, CDC; 1974. Available at http://stacks.cdc.gov/view/cdc/7663. Accessed September 17, 2012.
  8. Lambropoulos AS, Fine JB, Perbeck A, et al. Rodent control in urban areas—an interdisciplinary approach. Environ Health 1999:12–7.
  9. Colvin BA, McCartney WG, Ashton AD, Jackson WB. Planning rodent control for Boston's central artery/tunnel project. Davis LR, Marsh RE, eds. Proceedings of the 14th Vertebrate Pest Conference. Davis, California: University of California, Davis; 1990:65–9.
  10. Drummond DC. Developing and monitoring urban rodent control programmes. Acta Zool Fennica 1985;173:145–8.

* Information available at http://www.nyc.gov/html/dcp/html/lucds/cdstart.shtml.

Information available at http://www.census.gov/prod/cen2000.

§ Available at http://www.nyc.gov/html/doh/downloads/pdf/pest/rodent_control.pdf.

Available at http://www.nyc.gov/rats.

** During indexing, inspectors looked for the same six ARS as during complaint-based inspections. However, indexing inspectors spent less time because they did not inspect the interior of buildings or individual units inside a multifamily building.

†† Including the following: not eligible because city-owned, no owner found, no access to the property, dangerous conditions, and employee error.


What is already known on this topic?

The Norway rat is a pervasive urban pest that is known to carry disease and cause extensive property damage. Active surveillance for rats can help public health professionals assess levels of infestation and track the success of interventions over time.

What is added by this report?

During December 2007–August 2009, New York City conducted three rounds of proactive indexing inspections for rat activity in an area of the Bronx. Results indicated that, among 29,996 properties, the percentage with active rat signs declined 54%, from 9.75% to 4.51%, and the percentage with severe rat infestation decreased 58%, from 0.48% to 0.20%.

What are the implications for public health practice?

Active surveillance for rats, publication of findings, enforcement of abatement orders including charges and fines, and education and outreach to neighborhood groups and property owners all are key components of a health department's rodent control strategy. In addition, by inspecting entire neighborhoods for rat activity, rather than single properties alone, action can be timed to have an impact at the neighborhood level and avoid displacing rats from one property to another.


TABLE. Properties with active rat signs (ARS)* and severe infestations, by neighborhood-wide indexing round — Bronx, New York, December 3, 2007–August 21, 2009

Indexing round

Period

Active rat signs

Severe infestations

%

%

Round 1

December 3, 2007–June 23, 2008

9.75

0.48

Round 2

July 14, 2008–December 30, 2008

5.83

0.27

Round 3

January 20, 2009–August 21, 2009

4.51

0.20

* Inspectors looked for any of six signs: 1) fresh tracks, 2) fresh droppings, 3) active burrows, 4) active runways and rub marks, 5) fresh gnawing marks, and 6) live rats.

Inspectors recorded a severity score for each ARS ranging from zero (sign not present) to three; total ARS scores ranged from zero to 18. Any property with a total ARS score ≥3 was considered to have a severe infestation.


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