Rodent Risks Rise

The onset of cool weather is traditionally a time for rodent invasion into structures of all types as the rats and mice seek shelter against the elements. But this year many areas of the U.S. are seeing an even greater increase in rodents due to last winter’s mildness and the spring’s heat wave; and the risk has risen due to an increase in Hantavirus infections from deer mice. The increased rodent problem began to emerge early in the spring, and is expected to continue into the winter.

“Most of the country had large increases in rodent populations,” said Jim Sargent, Copesan director of technical support and regulatory compliance. “Some facility managers are saying that they’ve never had so many rodent problems as they did earlier this year.” Although some areas are not seeing the increase, or any difference from prior years, Sargent cautioned that situations change. “You can’t let your guard down any time during the year, especially in the fall when weather changes,” he said.

“If we were to track and graph when rodents are found inside a facility over many years, there is usually a peak in the fall over most of the country,” he explained. Rodents are warm-blooded animals, like humans. Thus, in the northern states, once the first frost occurs, rodents, especially mice, seek winter shelter. “They must find a warm, sheltered place, or they will die when exposed to freezing temperatures for a few hours,” Sargent said.

As is true in virtually any contamination control program in food and beverage processing plants, the key to controlling rodents and keeping them from finding shelter in your plant is prevention. “Be aware of the facility surroundings,” said McCall Services Vice President of Operations Al Formella. Overgrown weeds and grass, as well as tree branches near the building will provide rodent harborage. This results in conducive conditions that could result in rodents entering exterior wall gaps as small as one-half inch. To guard against such harborage, Formella cautioned, stored items such as pallets should be kept well away from the building. This is especially true in areas such as shipping and receiving doors. “Even when doors are shut, they aren’t always rodent proof and sometimes exclusion modifications must be made.”

Roger Collins, McCall’s Jacksonville, Fla., branch manager seconded the advice, noting that special care should be taken around dock ramps. “Door sweeps that aren’t well sealed or that have been damaged by trucks backing in may be unnoticed after a previous year’s inspection,” he said.

And with the abundance of moisture and food it has to offer the rodents, a plant provides an ideal haven in which to spend the winter. “Aside from pest management control, rodents pretty much have it made after discovering their way inside,” said McCall Entomologist Larry Wise.

So how can rodent entry be prevented? Sargent provided a three-step plan:

• Rodent-proof every facility. This means no propped-open doors at anytime, no unrepaired holes or gaps, and no pencil-size (or larger) openings anywhere. “This is the time of year when you must not delay repairing or tightening your facility,” he said.
• Have an exterior rodent program to keep rodent populations down, at least next to the facility. Have no clutter or equipment stored outside and no spilled grain or other possible rodent food near the facility. Avoid vegetation near the building unless it is mowed very close to the ground.
• Be sensitive to changes in the weather and the environment every day—especially in the Fall. “When the first frost and freezing temperatures are forecasted, it’s time to strengthen your rodent defense for the next 30 days for the stampede that’s going to happen,” Sargent said. Also, watch for harvesting, plowing, or burning on adjacent properties. When rodent habitat is removed, there will be large numbers of homeless rodents seeking new shelter. When such environmental changes occur, Sargent advises that you immediately call your pest control operator (PCO) to increase your exterior rodent program—not tomorrow but immediately. A bit of rodent prevention now is much better than an expensive problem later.

Such prevention also includes inspecting the facility and maintaining a sanitary environment. Having a good, preventive sanitation program in place will head off many pest issues, Formella said. And a facility’s pest control provider can be a good resource for information on sanitation issues and other pest-related needs.

Particular attention should be paid to screens and siding, Formella noted. While screens on doors, windows, and exhaust vents can keep rodents out, these can become loose or torn over time—and it does not take a very large gap for a mouse or rat to sneak in. Siding is often unintentionally damaged by forklifts or may loosen over time or from weather. “Rodents can get easy access once it deteriorates,” Formella said.

Hantavirus. Rodents are also an issue because they are known to carry disease, and this year’s rise in Hantavirus Pulmonary Syndrome (HPS) infections from deer mice is further increasing that hazard. The summer saw early diagnoses, then an outbreak in Yosemite National Park has, so far, resulted in nine confirmed cases of HPS, three of which were fatal. Additionally, there were others seeming to have symptoms of the virus, but as of this writing, their symptoms were mild and unconfirmed as HPS.

If a mouse carrying Hantavirus were to get into your plant, it would not only pose a danger to employees, visitors, and your product, but it is a liability if you don’t have a good rodent prevention program in place.

Priority & Communication. In addition to prevention, it is crucial that plants have ongoing communication with their PCO, and that plant management be involved in this communication. “More times than not, plants are not giving the PCO access to the managers who make decisions on pest control,” said McCall President and CEO Bryan Cooksey. Cooksey recommends that this person meet with the PCO at least once a quarter, “so that you have communication up to the decision-maker level.”

“I think it starts with an understanding that there’s a partnership with the pest control provider,” Cooksey said. This includes establishing a plan together, tracking the plan and results, and establishing accountabilities. “The better you communicate on understanding needs, the better it works.”

High-level communication can also ensure that pest control needs are worked into the budget. Money may be needed for a structural upgrade or for updating or replacement of traps. If the decision maker is not in on the communication throughout the year, it can be difficult to convey the monetary needs come budgeting time.

However, while it is important to ensure that decision makers are involved in rodent control decisions, it is just as critical to ensure that floor workers understand the problems associated with rodents, Formella said. Many pest control providers can also conduct training sessions for plant employees to discuss the biology of rodents, points of entry, and the importance of reporting rodent sightings and evidence of their presence such as droppings.

Too often, plants put priority on pest control only before an annual third-party audit. But, Collins said, a lot can happen in a year. “If you could get the mentality in the plant that there is a high priority all the time instead of just before an inspection, it would help with control,” he said. Additionally, auditors check records, so if this priority is not being placed year-round, it will be verified in the documentation.

This documentation, in fact, can be of great assistance in controlling rodents, as well as all pests. For example, Formella said, reports may show a trend or prevalence of rodent activity in a specific area. Inspecting the area may show a structural fault, opening, harborage, or food—enabling you to zero in on why and how the rodents are coming in. “Sometimes the only way to identify that is through the trend reports.” And paying attention to such reports and implementing corrective action can become even more critical for preventing rodent incursion during years, such as this year, which show trends toward a general increase in rodent activity.

Additionally, the recent rodenticide label changes (See Rodenticide Labels Require Caution, sidebar above) may have an impact on rodent activity in and near processing plants, but, Sargent said, it’s difficult to know for sure. “If we average across the entire country for the next few years and compare against several previous years, I think that we will find more rodents getting into facilities and increasing the risk of contaminated food. However, I also think that we won’t be able to tell if the increased risk to food safety was because of the rodenticide label changes, weather, or the natural fluctuations of rodent populations.”

But, regardless of the cause, he added, “Most importantly, everyone needs to be vigilant and not let their guard down—rodents that get into your facility can shut you down.”

Lisa Lupo is Editor of QA magazine. She can be reached at llupo@gie.net.