From the 1900 San Francisco bubonic plague epidemic to the 2012 Yosemite National Park hantavirus infection outbreak, rodents have always been a lurking environmental threat, capable of compromising the public’s health. In addition to potentially carrying parasites and pathogens, rodents have been destroying infrastructure, infesting houses and businesses, and damaging property for centuries. To this end, NACCHO and the Centers for Disease Control and Prevention (CDC) assessed nine local rodent control programs across the United States to identify best practices, challenges, and technical assistance needs.

Rodent Control in the United States:

The three main rodent pests in the United States are the house mouse, Norway rat, and roof rat. Rodents transmit a large number of diseases, and in many places rodents live in close contact with humans. Rodents can directly transmit disease through feces, urine, or saliva or indirectly transmit disease through ticks, mites, or fleas [1]. As such, the United States has experienced outbreaks of rodent-borne diseases such as plague, hantavirus, leptospirosis, rat bite fever, and murine typhus fever periodically throughout history. Additionally, a recent study found that rats can be infected with bacterial pathogens known to cause gastroenteritis and infectious agents associated with febrile illnesses such as leptospirosis [2]. The study also identified known and novel viruses important to humans, including two new species that appeared to be similar to the hepatitis C virus. Rodents have also been linked to health problems associated with asthma and indoor allergic reactions [3].

Rodent control programs in the United States have been in operation for more than 100 years, though the different rodent control activities have changed significantly. For example, pest control efforts have moved away from traditional poisoning and trapping toward an Integrated Pest Management (IPM) approach. IPM manages pests and disease vectors through pest prevention, pest reduction, and elimination of conditions that lead to infestations through safe and effective interventions [4].

Survey Results

The goal of the study was to help NACCHO and CDC understand the current capacity of local rodent control programs across the United States and to identify best practices, challenges, and technical assistance needs of local rodent control programs. NACCHO and CDC invited nine organizations from diverse cities to participate in an assessment of their rodent control programs. The questionnaire contained sections that corresponded to the 10 Essential Public Health Services [5]. The nine organizations include:

• Austin/Travis County (TX) Health and Human Services Department;
• District of Columbia Department of Health;
• Los Angeles County Department of Public Health;
• Multnomah County (OR) Department of Public Health;
• New Orleans Mosquito, Termite, & Rodent Control Board;
• New York City Department of Health and Mental Hygiene;
• Philadelphia Department of Public Health;
• San Francisco Department of Public Health; and
• Shelby County (TN) Health Department.

Local rodent control programs face many challenges, including a lack of funding and resources. A majority of the programs are funded locally. Only two programs, Los Angeles County and Shelby County, are funded by service fees. In Shelby County, the program is fully funded through a state–legislated vector control fee. Overall, funding for a majority of the programs has either decreased or remained the same during the past five years. The five programs that noted a decrease in funds significantly reduced or adjusted staffing and activities. While many rodent control programs have seen positive outcomes as a result of their work, fluctuations in funding have made it difficult to sustain these positive outcomes in the long term.

Various aspects of the behavior and biology of rodents, such as reproductive potential, trap avoidance, and feeding behavior, complicate rodent control; therefore, rodent control is especially difficult when a program is solely complaint-based. All programs examined use IPM in their rodent control efforts and are primarily complaint-based; five programs conduct a variety of proactive activities. Generally, the number of complaints reported within the past year ranged from 10 to 2,000 per month, depending on the jurisdiction. All programs use a hotline for the public to report rodent problems and record and track public complaints. Some programs are more proactive than others with activities ranging from selective baiting of manholes to conducting hundreds of thousands of inspections. In New York City, the Rodent Reservoir Analysis project identified and studied “rat reservoirs” in local neighborhoods. Inspectors set bait for the rats, closed up burrows, and worked with the community on best practices. Philadelphia’s program staff includes mechanics who perform rat-proofing services each year, such as repairing plumbing and filling holes. None of the programs track rodent-borne illnesses or rodent-related injuries and/or bites, but they do rely on notifications from their agencies’ epidemiology divisions. No human cases of rodent-borne diseases were confirmed in the past year, although some programs reported rodent-related injuries and/or bites.

Additionally, property and business owners may lack understanding of rodent control. Local rodent control programs that engage in proactive public education can prevent a misinformed public. The lack of training opportunities is a continual challenge for many of the local rodent control programs assessed. Program staff must have up-to-date knowledge of rodent control, including rodent biology and behavior, IPM practices, and response strategies. Public education is a priority for every program surveyed. All programs inform the public about the importance of rodent control; for example, New Orleans offers a Pest Control Academy, and San Francisco holds educational meetings with the San Francisco Professional Gardeners Association. Programs disseminate rodent-related information through pamphlets and online resources. The Washington, DC, program aims to educate the public and change behavior to mitigate the determinants of rodent activity. It works closely with the DC Department of Public Works to provide live, public web chats or “Rat Summits” to discuss rodent control practices. Austin’s rodent control program successfully educates and reaches out to many different populations in the area, such as the Spanish-speaking community, through translated fact sheets and other resources. To ensure a competent workforce, all programs have processes to ensure that employees are properly certified and attend ongoing education and training courses. However, all programs expressed a desire for more staff training opportunities that include lectures, field work, and laboratory work. New York City has developed its own Rodent Academy, which provides training and courses on IPM; biology, behavior, and habitat of rodents; contributing factors to infestation; effective ways of evaluating site-specific responses and strategies; and effective communication strategies. Since 2005, the three-day academy has trained more than 2,000 individuals from all over the United States.

What Local Health Departments Can Do:

With enough staff, funding, public education, resources, and technology, rodent control programs could be even more successful. Framing rodent control as a public health issue and encouraging collaboration among public health professionals and their communities will help create long-term and more successful solutions to control rodent populations and keep rodent-borne diseases at bay.

Seven case studies summarizing each agency’s rodent control program as well as an executive summary are currently available for download on NACCHO’s website.

NACCHO would love to hear about the local rodent control work your agency is conducting. Please email us or comment below!