The most common rodent to infest schools and childcare centers, and make a pest of itself is the house mouse (Mus musculus). The scientific name is quite appropriate, as musculus is Latin for "little mouse," and mus is an ancient Sanskrit word which means "thief." The house mouse will be found wherever there are people and prefers a life of stealing human food and living in human shelters. This makes it a common pest in both urban and suburban areas throughout Indiana. House mice may infest buildings throughout the year, but are especially likely to show up during thecold weather months when it is much easier to find food and stay warm inside human structures, than to survive outdoors.
The problem with having mice indoors is that they can cause extensive damage to food supplies, possessions, and equipment, and may transmit diseases and parasites to humans. Mice are rodents whose teeth never stop growing throughout their lifetime. Thus they must continuously gnaw to keep their teeth from getting too long, and to keep them sharp. Gnawing may result in the destruction of books and papers, and the loss of important documents, or result in fires or costly computer crashes as a result of gnawed electrical wiring. House mice can also destroy huge amounts of stored food. Although they don't eat a lot per day, they have the habit of nibbling on a wide variety of items and leave partially eaten foodstuffs strewn about. In addition, they have the unpleasant habit of urinating and defecating wherever they eat, contaminating as much as ten times as much food as they eat. Food contaminated with mice feces may result in the bacterial food poisoning salmonellosis. Certain tape worms can be spread through house mouse droppings, and ringworm can be carried to humans through mice. Also, the house mouse can be a major carrier of leptospirosis (Weil's disease). Rickettsial pox and dermatitis may be caused by the bite of the house mouse mite, which is found wherever there are mice present. Both meningitis and hantavirus may be transmitted through contaminated food, or the breathing of airborne particles of urine, droppings, or saliva. Infection of hantavirus may also occur when dried material contaminated by excrement gets ingested, or introduced into broken skin or body orifices (rubbing of the eyes, nose, or mouth, with a hand that has been in contact with contaminated food, dust, or nest material). There is a greater than 0% mortality rate among people that contract hantavirus, and it has been found in Indiana rodents.
House mice are most often a dusky gray or brown color, but may be any of a variety of colors, ranging from very light gray to almost black. Adults are about one inch tall, and 3-4 inches long, not including the tail. They live in extended families, or colonies, with each colony establishing a territory by marking boundaries with urine and droppings. When infesting schools, droppings are frequently the first indication that there are mice in the building. The chances of actually sighting a mouse are fairly slim, unless they have lived in the building long enough so as to lose some of their fear. This is due to the fact that mice are primarily active at night, and although they have poor eyesight, their bulging eyes allow them to detect movement in any direction. Mice also have a keen sense of hearing. They are very sensitive to small, and have no problem detecting food, even if it is packaged, unless the food is in an airtight container.
House mice give birth about 19-20 days after mating, and have between 4-13 pups, averaging about 7 per litter. Each female will typically produce 8-10 litters per year for a total of between 50-70 pups. The young mice will be able to breed for the first time between 5 and 8 weeks after birth. Nests are made in dark secluded places out of cloth, chewed paper, or any other soft material available.
There are few places mice cannot go. They have tactile hairs (whiskers) around their mouths and nose, and above their eyes, as well as on the sides of their bodies and legs. These hairs let a mouse know quickly if a tiny opening is large enough for its body. It can squeeze through openings slightly more than a quarter-inch in diameter, or about the size of a dime. They are also excellent jumpers and climbers. Mice are able to jump to and from great heights, and can climb any grippable vertical surface. They are known to climb wood, brick, pipes, cables, rope, girders, and wire mesh. They may also gain access by simply gnawing through a barrier, and they are not averse to swimming.
What enables us to control mice is their predictability and their curiosity. Mice will explore their territory daily, and establish routes of travel which they utilize again and again, creating high traffic areas. They will also thoroughly investigate any disturbance, or new item in their territories, including traps.
The first visible sign that there are mice in the building will probably be droppings. A house mouse will excrete about 70 droppings per day. Also, be on the lookout for small tooth marks or wood chips the size of coarse sawdust around baseboards, doors, windows, and cabinets, and for nest materials, such as finely shredded paper, cardboard, cloth, etc. Watch for footprints or tail marks on dusty surfaces. Since mice mark their territories with urine, which will fluoresce under ultraviolet light, urine stains can be detected through the use of a blacklight. In addition to visual monitoring, place snap traps in areas of suspected entry and past mouse activity. Check these monitor traps often.
The first step in controlling mice is to deny them food and shelter. Sanitation and cleanliness are of the utmost importance. Not only will this reduce the attractiveness of the school for house-hunting mice, if mice do decide to live in the building, this enables their early detection, as new droppings are more obvious. It will also increase the effectiveness of traps by reducing competing food sources.
In addition to general building cleanliness, keep all food, including any pet food, water, or birdseed in classrooms, tightly sealed in mouse-proof containers off the floor. Clean up spilled food. Wash dirty dishes and utensils. Remove any uneaten food immediately. Store garbage in metal or thick plastic containers with tightly fitting lids. Remove garbage often, and dispose of and avoid clutter which might shelter mice.
In addition, every effort should be made to mouse-proof the building. Seal all openings which are larger than a quarter-inch in diameter to prevent mice from entering. Effort should be placed on discouraging mice from residing near the building by removing clutter and debris around the exterior, and by removing weeds, tall grass, brush, and dense shrubbery from around the building. This will remove shelter and food from the vicinity of the school or childcare center and discourage mice from inhabiting areas where they could be tempted to enter.
If mice are discovered, the best method of control is the common snap trap. Be sure to use enough traps to make the eradication effort short. Good trap sites are along walls, behind objects, and in dark corners. Place traps along, above, below, and adjacent to known activity areas, but keep in mind that traps should be inaccessible to curious children. Attractive baits include peanut butter, bacon, raisins, nutmeats, hotdogs, cereal, popcorn, and especially cotton balls. For best results, tie the bait to the trigger with a thin string or dental floss, and place the trap perpendicular to a vertical surface, with the trigger next to this surface. Check traps at least once a day. If mice are discovered, be sure to contact the IPM Coordinator for advice, assistance, and supplies. NEVER TOUCH DEAD MICE. When removing dead mice, wear rubber gloves, and a protective mask over your nose and mouth to prevent ingestion of aerosolized excrement or contact with mouse mites. Place the dead mouse in a sealed plastic bag, and dispose of it in a trash receptacle which is not accessible to students.
When cleaning in a mouse-infested or formerly infested area, you should also wear a mask and gloves. Do not sweep or vacuum the area, as this will aerosolize excrement and contaminated dust. Mop the area using a solution of water and a general purpose household disinfectant to kill disease, and dispose of any cleaning rags or paper towels in a sealed plastic bag. Contaminated carpet should be shampooed or steam cleaned, rather than vacuumed.