by Nick Gromicko, CMI®
Rodents are a problem not just because they can destroy personal property and create problems with a home's structure, but also because they can spread serious diseases to humans and their pets. Rodent-borne disease may be spread directly -- by touching rodents or their
urine, feces or saliva -- or indirectly -- by coming into contact with fleas or other insects that have fed on an infected rodent host. Inspectors should use extreme caution and wear appropriate personal protective equipment when entering a home that is known to be infested with rodents.
Some diseases resulting from direct contact with mice and rats include:
- hantavirus pulmonary syndrome;
- hemorrhagic fever with renal; syndrome;
- Lassa fever;
- lymphocytic chorio-meningitis;
- rat-bite fever;
- South American arenaviruses; and
Some diseases resulting from indirect contact with mice and rats include:
- Colorado tick fever;
- human granulocytic anaplasmosis;
- lyme disease;
- murine typhus;
- scrub typhus;
- relapsing fever; and
- Rocky Mountain spotted fever.
Rodents also pose a danger to the integrity of the structures they inhabit. They have strong teeth and they may chew through structures to gain access to food sources. The best method for preventing exposure to rodents is to prevent rodent infestation in the first place, according to the Centers for Disease Control (CDC) and the U.S. Environmental Protection Agency (EPA).
How can you tell that a home is infested?
Actual rodent sightings in the home are a good indicator that a severe infestation may be in progress. Mild cases of infestation might not result in actual rodent sightings.
Indicators of an infestation are:
- chewing or clawing sounds that come from inside or outside a home. Noises may even come from the roof, as tree-dwelling rodents may try to gain access to a home from above the living space;
- stale smells coming from hidden areas;
- evidence of structural damage that can provide entry points into the home;
- evidence of gnawing and chewing on food packaging;
- nesting material found in small piles, such as shredded paper, fabric or dried plant matter; and
- rodent droppings anywhere in the home, especially near food packages in drawers and cupboards, and under the sink.
How can rodent infestation be prevented?
The following measures can be taken to eliminate rodents' food sources, according to the CDC:
- Keep food in thick plastic or metal containers with tight-fitting lids.
- Clean up spilled food right away, and wash dishes and cooking utensils soon after use.
- Keep outside cooking areas and grills clean.
- Always put pet food away after use and do not leave pets' food or water bowls out overnight.
- Keep bird feeders away from the house. Utilize squirrel guards to limit access to the feeder by squirrels and other rodents.
- Use thick plastic or metal garbage cans with tight-fitting lids.
- Keep compost bins as far away from the house as possible.
- Dispose of trash and garbage on a frequent and regular basis, and eliminate clutter in and around the property to discourage nesting.
Mice can squeeze through a hole the size of a nickel, and rats can squeeze through a hole the size of a half dollar, according to the CDC. Consequently, smaller gaps may be filled cheaply and easily with steel wool and caulk may be used to seal it in place. Larger gaps and holes may be filled with lath screen or lath metal, cement, hardware cloth or metal sheeting.
Common places where gaps may be found inside the home are:
- inside, under and behind kitchen cabinets, refrigerators and stoves;
- inside closets near the floor's corners;
- around the fireplace;
- around doors;
- around plumbing pipes under sinks and washing machines;
- around the piping for hot water heaters and furnaces;
- around floor vents and dryer vents;
- inside the attic;
- in the basement or crawlspace;
- near the basement and laundry room floor drains; and
- between the floor and wall juncture.
Common places where gaps may be found outside the home are:
- in the roof among the rafters, gables and eaves;
- around windows;
- around doors;
- around the foundation;
- near attic vents and crawlspace vents;
- under doors; and
- around holes for electrical, plumbing, cable and gas lines.
Any potential nesting sites outside the home should be eliminated. Elevate hay, woodpiles and garbage cans at least 1 foot off the ground. Move woodpiles far away from the house. Get rid of old trucks, cars and old tires that mice and rats could use as homes. Keep grass cut short, and keep shrubbery within 100 feet of the home well-trimmed.
What should be done if a house is found to be infested with rodents?
It is important to stay away from rodents, and to protect children and pets from direct and indirect contact if they are found in the home. Droppings should be handled only with extreme caution, even if they have dried. A face mask and gloves should be worn if handling and cleaning up these droppings because disturbing fecal particles may precipitate airborne contaminants. Affected areas should be sterilized after the droppings have been removed.
In mild cases of infestation, homeowners may choose to eliminate the rodents themselves. They should make sure to take preventative measures while doing so. To remove rodents, homeowners will need to use traps or rodenticides.
Some different types of traps include:
- lethal traps, such as snap traps, that are designed to trap and kill rodents;
- live traps, such as cage-type traps, that capture rodents alive and unharmed, requiring that the rodents then be released or killed; and
- glue boards, which are low-cost devices that use sticky substances to trap rodents, requiring a further decision regarding disposal, since such traps are not lethal.
Traps should be set in any area where there is evidence of frequent rodent activity. Some rodents, particularly rats, are very cautious and several days may pass before they approach the traps. Other rodents, such as house mice and deer mice, are less cautious and may be trapped more quickly. Glue traps and live traps may scare mice that are caught live, causing them to urinate. This may increase a homeowner's risk of being exposed to diseases, since the rodent urine may contain germs or disease-borne pathogens.
Rodenticides are products intended to kill rodents, and are typically sold as powders in bait and tracking form. Some rodenticides include:
- baits, which combine rodenticides with food to attract rodents. They may be formulated as blocks or paste and may be enclosed in a bait station;
- tracking powders, which are rodenticides combined with a powdery material. The powder sticks to the rodents' feet and fur and is swallowed when the animals groom themselves. After consuming the chemical poison contained in the bait or tracking powder, the rodents die. Some rodenticides (including tracking powders) may be legally applied only by certified pesticide applicators because they may pose a risk to human health.
The following measures should be observed when an infestation is being eliminated:
- Traps and baits should be placed in areas where children and pets cannot reach them.
- Products should be used according to the label's directions and precautions.
- Only traps that are appropriate to the type and size of the targeted rodent should be used.
- Glue boards should be placed in dry, dust-free areas, as moisture and dust will reduce their effectiveness.
It is advisable to contact a professional exterminator to deal with more severe infestations, since rodents reproduce constantly and quickly.
In summary, rodent infestation poses a serious risk to human health, and extreme caution must be taken when eliminating the problem.