For those of us who live on the edge of a forest, one of the most insidious dangers is brought into our homes by one of the cutest of
forest creatures, the deer mouse. Having just had to wage my distressing Annual Deer Mouse Massacre last night, this may be a good time to provide a warning about
just how serious the problem is.
First, a caution - don't get too focussed on this, as the disease is quite rare. However, it is fatal to almost half the people who contract it,
so it's important to know the situation, and the easy steps to take to avoid exposure.
Hantavirus Pulmonary Syndrome (HPS) was first recognized in the United States in 1993. The circumpolar North, however, has known hantavirus outbreaks
for decades - in Europe, different varieties of the virus occur, with different carriers than in North America. In 1913 Russia was hit hard by the disease, then in
1932-1935 most of Scandinavia saw outbreaks, and in 1945 a small area of northern Finland was hit. In Canada, the earliest confirmed case of HPS dates to 1989.
Most cases in Canada have been in the area of Edmonton, Alberta, but as of January 2013, a fatal case occurred in the village of Atlin, in the remote north-west corner of British Columbia.
Deer Mice (Peromyscus maniculatus) have large eyes and ears, with bodies about 2.5 - 3.5 inches long and tails the same length. Colors range
from grey to reddish brown. The most distinctive feature is a white underbelly; the feet and tail may also have some white on them. Deer mice inhabit most of North
America, including much of the Yukon and Northwest Territories.
The greatest danger of contracting HPS is from mouse feces, and in most North American cases, this occurs while cleaning out cabins or working on farms.
A mouse nest (burrow) is usually a small pile of grass, twigs or insulation, and the droppings look like black, cooked rice grains. Disease transmission most commonly
occurs when rodent droppings are disturbed and the resulting dust is inhaled, so it's important to not used dry cleaning methods; do not clean up droppings or dead mice
with a blower, vacuum, or hand broom!
The average time between contact with the virus and the onset of illness is two to three weeks. Unfortunately, the initial symptoms
look very much like the flu, including fever, muscle ache, cough, headache, nausea, and vomiting. If you develop a fever or respiratory illness that rapidly
gets worse and includes shortness of breath, seek immediate medical attention. Inform the doctor that you have been in contact with deer mice, and that you suspect
possible Hanta Virus infection. There is not yet (January 2013) an approved antiviral treatment available for HPS. Tests with Ribavirin in the late 1990s initially looked promising, but turned out to be ineffective.
Prevention of Hanta Virus Infection
To minimize the risk of Hanta Virus infection, rodent populations must be controlled.
- General cleanliness is very important.
- Get rid of trash, abandoned machinery, discarded tires, and other items that could serve as rodent nesting sites.
- Use commercial traps, rodenticides, or ultra-sonic devices.
- Seal all openings of more than a quarter-inch diameter. Use metal flashings at the base of wooden or earthen structures. Gravel under structures helps
- Keep food and garbage in rodent-proof containers. Trash should be disposed of promptly.
- Cut grass, brush and dense shrubbery within 100 feet of buildings.
Even with the most fastidious control program, some contact with rodents and/or their droppings is inevitable around cabins and farms.
When working in areas where mice have lived, observe the following precautions:
- Any enclosed area should be aired out for at least 30 minutes before cleanup begins.
- Always wear rubber gloves when cleaning up rodent carcasses and droppings, or when handling traps.
- Wear a respirator that has a HEPA (P100) rating. Ordinary dust masks will not filter the virus!
- If there is evidence of a lot of rodent activity, wear disposable coveralls. Any exposed clothing should be washed separately from the regular family
laundry. Handle clothing with gloves. Wash in hot water and detergent, and dry in a hot dryer.
- Before starting cleanup, thoroughly wet down the area with a 10 percent household bleach solution (3 tablespoons of bleach in one quart of water).
- Use only wet cleaning techniques, such as damp mopping. Avoid sweeping, vacuuming and other dry cleanup techniques.
- You should dispose of dead mice by dampening the body with the spray solution, picking it up with gloves, and placing it into a plastic bag. If possible,
burn the bagged material.
- After cleanup, disinfect the entire area with a 10 percent bleach solution. Allow the area to dry thoroughly before entry or use.
- All traps should be disinfected in a bleach solution.
- Before removing rubber gloves, wash them in a bleach solution, and then with soap and water. Wash your hands upon removal of the gloves.
References & Further Reading:
Center for Disease Control
A comprehensive for of information on HPS - symptoms, treatment and prevention of exposure.
Deer Mouse (genus Peromyscus)
Information from Wikipedia.
Northern Health & Welfare Links
Deer mouse photo is © by the US Dept. of Health & Human Services - used here with permission.