Reducing Disease Potential

“Rats and mice are commensal rodents, meaning they see our home and food as their home and food,” said Matt Frye during the recent PCT Rodent Control Virtual Conference. Frye works for the New York State IPM Program at Cornell University. He provides education and researches pests that occur in and around buildings where people live, work, learn and play.

“The problem with these rodents is that they can harbor human pathogens that can harm us, as well as our pets and other companion animals,” he said.

For example, rodents can walk through sewage and then transfer pathogens to food preparation surfaces and other areas that humans may contact.

“This is why they’re such terrific pests,” Frye said. “They can transmit these pathogens but not be affected by them the same way we are because they have a different immune system.”

Frye said that while the professional pest management industry may understand the risk rodents pose to human health, most professionals servicing residential and commercial accounts don’t think the public understands and appreciates the health implications of rodents.

CURRENT RISKS. Some of the risks Frye says industry professionals can communicate to their clients include:

Electrical fires: “It’s estimated that 25 percent of fires of unknown origin are caused by rodents chewing on wires in walls,” he said. “Rodents probe wires thinking that perhaps there are insects inside or some kind of liquid they may be able to drink.”

Landscape damage: Rodent burrowing behavior can lead to destruction of ornamental plantings when rodents chew on roots.

Product contamination/destruction: Rodents are capable of getting into food and product packages and causing damage.

Pathogens: “Rodents are carrying a huge diversity of pathogens,” Frye said. “One of the alarming trends that has been found in both New York City and Vancouver is that rodents are also carrying antimicrobial resistance genes. This means that the pathogens they are carrying may be resistant to the antibiotics and antimicrobials that we use to treat those pathogens. So, there is a real risk to people in urban areas based on rodents living near us.”

With limited research in non-urban areas, present risks are unknown. However, Frye said it is known that rodents have been associated with diseases such as bubonic plague, murine typhus, Lyme disease, rat-bite fever, hantavirus, food-borne illnesses and febrile illness. He noted that salmonella (the leading cause of foodborne illness in the U.S.) can be viable in rodent droppings for up to 86 days. Rodent-borne pathogens can cause symptoms varying from pain and discomfort to death.

PATHOGEN TRANSMISSION. Humans can be exposed to pathogens through direct transmission when they come into direct contact with a rodent or rodent evidence (feces/urine), or through indirect transmission when a vector (fleas, mites, ticks) transmits the pathogen from rodent to human.

Direct transmission: Frye said rats will bite in defense or when foraging on food spills and residues. This can happen to children in cribs or the elderly with food spillage on their mouths or hands. “Rodents will climb onto that person or climb into a crib smelling the food odors and may actually bite, probing for food,” he said. It also can happen if a person picks up a live rodent. “From 1986 to 1994 in New York City, there was a report of about 800 bites. So, this is a phenomenon that does occur.” Some pathogens also could be inhaled or ingested.

Also, while feces may not be in view, fecal pellets could be directly overhead, such as in drop ceilings or on pipes, and could fall onto contact surfaces. That would lead to exposure, says Frye.

Indirect transmission: An example of indirect transmission would be when ticks feed on an infected rodent. “That tick is now infected and, for the rest of its life, can potentially transmit those pathogens to another host,” Frye said. That may be to a rodent, person or other small animals. The diseases ticks carry vary by species. For example, the blacklegged tick is the only species that can transmit Lyme disease, and is the No. 1 vector-borne disease in the United States. “Estimates are that there are 300,000 cases of Lyme disease each year in the United States,” Frye said. “So, this is a really huge risk for people.”

HISTORICAL PLAGUES. Frye reviewed several historical plagues caused by rodents:

• Justinian Plague (541 AD): claimed 25 million lives over 200 years
• Black Death (1334 AD): killed 60 percent of European population
• Modern Plague (1860s): claimed 10 million lives in 20 years

It wasn’t until the 1860s when scientists finally identified the causative agent in terms of the bacteria and how the whole transmission cycle worked, said Frye.

The plague is still around, but it’s not the same “menacing threat” that it was in historical times, he says.

SIGNS OF ACTIVE RATS. Frye says that rodents can have “clumped” distributions. While sometimes there are no signs of their presence, other times rats will leave fresh tracks and droppings, active burrows and runways, and fresh gnawing.

“Rodents can travel far distances, but when resources are available close they will stay near that nesting site,” he said. “It’s interesting to note that a high-density area can be directly adjacent to a low-density area.”

This social living in persistent populations can enhance transfer of pathogens and parasites.

SAFETY CULTURE. Frye warned that working with rodents on a regular basis puts pest control technicians at elevated risk of exposure to pathogens.

“We definitely are at risk,” he said. “Exposure to pathogens from area to area can be unknown.” Pest management professional exposure to rodent-borne disease is likely elevated in confined spaces, when removing feces and when handling carcasses and traps. “In all these instances, we really want to institute a culture of safety.”

While medieval plague doctors wore masks and thick robes and carried knives and staffs, modern technicians have access to more effective gear.

“Me, personally, if I’m sending a technician into a crawlspace, especially with a dirt floor in a warm environment with some moisture, I want to recommend full-on personal protective equipment (PPE) to protect them against any fleas or other parasites that may be in that space,” Frye said (see box below).

PPE Recommendations

• Hard hat
• Tyvek suit
• Hairnet
• Gloves
• Respirator
• Boots
• Headlamp

Cleaning contaminated surfaces: Frye recommends visiting CDC’s website (www.cdc.gov/rodents/cleaning) for information regarding the safe removal of droppings. Some general tips include:

• Ventilate the space
• Wear gloves
• Use a solution of 10 percent bleach or disinfectant to saturate droppings before they are removed with a paper towel or HEPA vacuum and properly disposed of

Cleaning rodent bait stations: Don’t just brush or dump them out. If outdoors, Frye recommends dumping them into a container with a plastic bag that can be tied up and disposed of.

Hantavirus protection: A half-mask air purifier is recommended, as well as HEPA vacuums to remove droppings.

Rodent carcass management: Similar to rodent dropping clean up, collect carcasses, and treat with a bleach or other disinfectant solution over a gloved hand. Double bag if necessary and discard according to state regulations.

“This may seem extreme, but is critical, especially in urban areas where the risk of pathogens has been documented,” Frye said.

Ectoparasites: In cases with a trapped mouse, lice or other ectoparasites may leave the body in search of another host. “This is where I like to recommend exclusion,” Frye said. “Whereas trapping can minimize problems, successful exclusion can prevent problems.”

The Scientific Coalition on Pest Exclusion offers resources on material and tool selection (https://buff.ly/2KOUGi1).

COMMUNICATING RISKS. Frye recommends educating clients about rodent-borne diseases in terms of exposure to feces, urine, dead animals, allergens and ectoparasites. Explain that employing a professional pest manager often leads to quick and efficient elimination. “I do recommend avoiding fear tactics because honestly, the facts are scary enough,” he said.

Also, Frye recommended pest management professionals not make promises or guarantees that the service will eliminate or prevent rodents. “Instead, suggest you are reducing or limiting exposure,” he said. “When you make a guarantee of prevention, you’re unlikely to achieve that goal.”

Also, be careful about warranty wording. “I wouldn’t use the term ‘sanitize’ if you are providing dropping removal services because this implies that you are killing all of the pathogens,” he said. Instead, state that you’ll remove the droppings and clean up the area and provide CDC guidelines to limit liability about in-house cleaning information.

BUSINESS OPPORTUNITIES. The disease potential of rodents can provide PMPs with significant business opportunities. Offer exclusion as a preventive service and sanitation services to remove droppings and allergens, says Frye.

Also, consider certifications such as NPMA’s QualityPro certification in public health (https://buff.ly/2GZHl3a).

The author is an Ohio-based freelance writer.