Search the premises thoroughly when looking for signs of house mice. Search areas should include attics, basements, crawl spaces, around foundations, and behind and under stored materials. In addition finding urine or droppings, snap traps, and non-toxic bait may be used to confirm the presence of mice. Non-toxic tracking dusts, such as flour or talc, may be helpful.
Signs and visual confirmation have limited value in accurately estimating numbers of house mice, but they are the simplest and often the only practical methods available. With experience, you will learn what constitutes a minor, major, and serious infestation of house mice.
Damage to Structures
Mice cause damage to structures through gnawing and nest-building. In livestock confinement facilities and similar structures, they quickly can cause extensive damage to insulation inside walls and attics (Figure 6). Such damage also occurs in homes, apartments, and commercial buildings.
Mice often damage large electrical appliances by chewing wiring and insulation, resulting in short circuits, fire hazards, and other costly malfunctions.
Mice also damage items stored in attics, basements, garages, and museums. Heirlooms, paintings, books, documents, and other such items often are impossible to replace if they are damaged by mice.
Damage to Livestock and Pets
In homes and commercial buildings, mice may feed on stored food items and pet foods. They contaminate food with their urine, droppings, and hair. On farms, they damage structures that store feed and equipment. Mice often act as reservoirs or vectors of diseases, such as swine dysentery, leptospirosis, and salmonellosis.
Damage to Landscapes
Mice consume fresh vegetables, such as cucumbers, tomatoes, beans, peas, as well as fruits. They gnaw on the bark of young trees, feed on newly planted grain, and cause damage to crops before harvest. Contamination of food with droppings and urine makes it unfit for human consumption.
Health and Safety Concerns
Mice may bite when handled or trapped on glueboards. Always wear gloves when handling wildlife. Mice and their parasites transmit salmonellosis (food poisoning), rickettsial pox, and lymphocytic choriomeningitis to humans. Mice also may carry leptospirosis, rat bite fever, tapeworms, and the organisms that cause ringworm, a fungal skin disease of humans. Urine of mice may be an asthmatic trigger in some people.