Deer mice, though small, carry health concerns. These common rodents can introduce risks into human habitats. Understanding their characteristics and the diseases they transmit is important for public health. This knowledge helps in assessing risks and implementing exposure reduction measures.
Identifying Deer Mice
Deer mice (Peromyscus maniculatus) are small rodents, measuring 119 to 222 mm (4.7 to 8.7 inches) in length, including their tail, and weighing 10 to 24 grams. They have grayish to reddish-brown fur on their backs, contrasting with white undersides and feet. Their bicolored tail is dark on top and white underneath. They also have large, prominent black eyes and large ears with minimal fur.
These mice inhabit a wide range of environments across North America, from Alaska to central Mexico, excluding some southeastern U.S. coastal areas. They are common in rural areas like forests, grasslands, brushlands, and agricultural fields. While preferring outdoor settings, deer mice may seek indoor shelter, especially during colder months, entering homes, sheds, garages, or unused vehicles. Inside, they might nest in storage boxes, wall voids, or attics.
The Primary Health Risk: Hantavirus
Deer mice are primary carriers of hantaviruses, which cause Hantavirus Pulmonary Syndrome (HPS), a severe and potentially deadly respiratory illness. They transmit the virus primarily through urine, droppings, and saliva, shedding it without symptoms. Disturbing contaminated materials, like during sweeping or vacuuming, can release airborne viral particles for inhalation. Less commonly, transmission can occur through a rodent bite or by touching contaminated surfaces before touching the nose or mouth.
Symptoms of HPS manifest 1 to 8 weeks after exposure. Initial symptoms resemble a flu-like illness, including fever (above 101°F or 38.33°C), fatigue, and muscle aches, particularly in large muscle groups. Other early symptoms include headaches, dizziness, chills, and gastrointestinal issues like nausea, vomiting, or abdominal pain. As the disease progresses, typically 4 to 10 days after initial symptoms, severe respiratory problems emerge. Patients may experience coughing, shortness of breath, and chest tightness as fluid accumulates in the lungs, potentially leading to rapid heart rate and low blood pressure.
HPS is rare, but its progression is swift and life-threatening. The virus weakens lung blood vessels, causing fluid accumulation in air sacs and making breathing difficult, which in severe cases can lead to shock and organ failure. The fatality rate for HPS can range from 30% to 60%. Prompt medical attention is important if flu-like symptoms develop after potential rodent exposure. No specific cure or vaccine exists for HPS; treatment focuses on supportive care, often requiring oxygen therapy and mechanical ventilation in intensive care.
Preventing Exposure
Preventing exposure to deer mice and hantavirus involves practical steps, especially where rodents might enter human dwellings. Sealing entry points is a primary method to keep deer mice out of buildings. Mice can squeeze through openings as small as a quarter-inch. Seal any cracks or holes larger than this size in foundations, around pipes, and utility lines using materials like steel wool, caulk, or metal sheeting.
Maintaining a tidy outdoor environment also makes properties less attractive to rodents. Keep lawns mowed, trim shrubs away from the house, and store woodpiles at least 20 feet from structures.
Safe cleanup procedures are crucial for rodent droppings, urine, or nests to avoid aerosolizing the virus. Follow these steps:
- Before cleaning, ventilate the area by opening windows and doors for at least 30 minutes.
- Wear protective gear, including rubber or plastic gloves.
- Avoid sweeping or vacuuming dry contaminated materials, as this stirs up viral particles.
- Instead, wet down droppings, nests, and contaminated surfaces with a disinfectant solution (e.g., 1.5 cups household bleach per gallon of water, or a general-purpose disinfectant).
- Allow the solution to soak for 5 to 10 minutes.
- Wipe up materials with paper towels or rags, then double-bag and dispose of them in a sealed garbage can.
- After cleanup, wash gloves with disinfectant or soap and water before removal, then thoroughly wash hands.
Proper food storage in thick plastic, metal, or glass containers with tight-fitting lids also denies rodents a food source, discouraging their indoor presence. For significant infestations, professional pest control may be necessary for complete eradication and safe remediation.