Mice carry deadly hantavirus: tips for controlling them

The deer mouse, a known carrier of the deadly hantavirus, sometimes also invades homes and outbuildings. The infected deer mice excrete the virus in their droppings, urine, and saliva, and humans can contract the virus from breathing in airborne particles or from being bitten. Over 70 cases of hantavirus pulmonary syndrome have been reported in Canada. Except for a single case in Quebec, all of the cases occurred in the four western provinces.

The deer mouse has a distinctive colour pattern and is grayish to light brown on top, with a white belly. It has large ears, prominent “bug out” eyes, and a furry tail. The typical house mouse is usually entirely gray or light brown, although some house mice have light brown backs and their bellies are light brown (not white).

Mice generally prefer to eat cereal grains, but they can nibble at many different foods. They are excellent climbers and can run up rough vertical surfaces. They also can squeeze through a crack as small as one centimetre (3/8 inch).

How to control mice?

Mice are more common and more difficult to control than rats. Here are some tips:

Exclusion and sanitation

• Exclusion is a very successful and permanent form of rodent control. Mouse proofing involves sealing or covering all openings to your house.

• Good housekeeping and sanitation will help prevent mice from becoming established in a building. Pay particular attention to eliminating places where mice can find shelter and food.

Trapping and baiting

• Several types of mechanical devices including multiple-capture live traps and snap traps can be used to catch mice. Traps can be baited with a variety of foods such as peanut butter, dried fruit, and marshmallows.

• Glue board traps are also effective for mice control. They catch and hold mice that attempt to cross them. Glue boards can also be used in some multiple-capture traps. Don’t use glue boards to catch deer mice, as captured mice often urinate and defecate while stuck to the trap, thus increasing the risk of your exposure to hantavirus.

• Poison baits formulated with an attractant (generally food) and a rodenticide (toxin) can be used as part of the mouse control programme. Bait stations can be established in non-food areas in and around the premises. Check bait stations regularly and replace bait if it gets old or moldy.

• Rodent repelling devices may not provide adequate control. There is little evidence that sound, magnetic, or vibration devices of any kind will drive established mice from buildings.

• For current chemical control options, consult your local pest control representative. Follow closely the directions and cautions on the label.

Rana Sarfraz is an entomologist and ecologist currently working at the University of British Columbia.