by Deborah Jeanne Sergeant
“All cities, suburbs and rural towns have Norway rats and house mice,” said Jody Gangloff-Kaufmann, coordinator of community integrated pest management for Cornell, who recently presented a talk on rodent management as part of a webinar on IPM.
In rural settings, many enticements attract rodents, including feed storage, feed troughs, pet food and crops. Less foot traffic is present to deter them and, in some cases, older structures that aren’t well sealed offer rodents easy access to food and shelter.
Rats can contaminate food, chew wires and pipes, cause structural fires, spread disease organisms, carry disease vectors such as fleas, bite humans, livestock and pets, destroy landscapes and undermine sidewalks and building foundations.
“Rats can do a ton of damage,” she concluded. “What’s important to us is the human exposure to pathogens. The direct transmission is when humans come into direct contact with rodents or rodent debris, its urine and feces. Indirect transmission is a vector like a flea or tick that live on the outside of the rodent.”
Gangloff-Kauffmann encourages use of IPM for controlling rodents, especially in light of the emerging infectious human diseases originating in animal species.
“IPM can reduce the use of rodenticides while improving the success of rodent management,” she said.
Excluding pests by securing structures represents one way to curb rodent proliferation. There is no “silver bullet” for rodent management, Gangloff-Kaufmann said – but it helps if the “build them out approach” is widespread, so the rodents have nowhere to go.
“All of this would lead to better pest management to protect human health,” Gangloff-Kauffmann said. “There’s a great diversity of microbes carried by rodents.”
These include known and novel viruses, including sapoviruses, caridoviruses, kobuviruses, parechoviruses, rotaviruses and hepaciviruses. A recent study also revealed three gastroenteritis varieties (E. coli, C. difficile and Salmonella enterica) as well as four febrile pathogens (Bartonella spp., Streptobacillius monilformis, Leptospira interrogans and Seoul hantavirus).
Parasite sampling showed fleas on the rodents in the New York City study. The disease vector parasites from the rats demonstrated “the need to fully characterize the diversity and distribution of ectoparasites on Norway rats and assess the role in vector-borne disease transmission,” Gangloff-Kauffmann said.
Two observed parasites on the rats were Oriental rat flea and spined rat louse. Though not detected in this study, the bubonic plague was caused by Yersinia pestis bacteria carried by the Oriental rat flea. The spined rat louse can transmit typhus.
Usually, food plants use bait outside and traps inside to abide by the rodent control plans required by federal law.
Gangloff-Kauffmann said that environmental conditions can affect how often rats visit control devices. She referenced a Cornell study with which she was involved that showed data on rat activity collected from bait/trap boxes at 12 locations in New York and Toronto (76 inside and 27 outside), looking at conditions effecting rat activity included shelter, box location, temperature, food, water, pathways, disturbance and access to buildings.
“The result of this research is that yes, environmental conditions influence rat movements,” Gangloff-Kauffmann said. “Trap catches and bait feeding increased with higher temperatures, proximity to food and water resources, lower disturbance, access inside buildings and shelter inside and outside.”
From these results, she said the placement of bait and traps every 30 to 50 feet is not optimal. “We can improve use of baits and traps by using them only where rodents are active,” Gangloff-Kauffmann said.
She concluded that, “more needs to be done to understand rodent disease potential and improve rodent management.”