Deer mice (Peromyscus maniculatus) are small rodents common across North America, inhabiting diverse environments from rural areas to human structures. Recognized by their large eyes, prominent ears, and bicolored tails, they are significant carriers of pathogens that can affect human health.
Hantavirus Pulmonary Syndrome
Hantavirus Pulmonary Syndrome (HPS) represents the most significant disease directly linked to deer mice in North America. The primary cause of HPS in the United States is the Sin Nombre virus (SNV), for which the deer mouse acts as the main reservoir. This severe respiratory illness is not transmitted from person to person but rather through exposure to airborne viral particles. Humans typically contract the virus by inhaling aerosolized urine, droppings, or saliva from infected rodents, particularly when contaminated areas are disturbed.
Initial symptoms of HPS often resemble the flu, including fever, muscle aches, fatigue, and headaches, and may also involve nausea, vomiting, or diarrhea. These symptoms can develop anywhere from one to eight weeks after exposure. As the disease progresses, usually within four to ten days after initial symptoms, fluid can accumulate in the lungs, leading to severe respiratory distress. HPS can be fatal, with estimates indicating a mortality rate of approximately 38% among those who develop respiratory symptoms.
Leptospirosis
Deer mice can also carry Leptospira bacteria, which are responsible for causing Leptospirosis, a bacterial disease. Transmission to humans primarily occurs through direct contact with infected animal urine or contaminated water and soil. The bacteria can enter the body through cuts, abrasions, or mucous membranes in the eyes, nose, or mouth.
Common symptoms in humans include fever, headache, and muscle aches, often accompanied by chills, vomiting, or diarrhea. In more severe cases, Leptospirosis can lead to jaundice, a yellowing of the skin and eyes, and may result in kidney damage. While often presenting with flu-like signs, the disease requires prompt medical attention.
Tick-Borne Pathogens
While deer mice do not directly transmit tick-borne diseases, they serve as reservoir hosts for ticks. Blacklegged ticks (Ixodes scapularis), commonly known as deer ticks, feed on deer mice, acquire pathogens, and can then transmit them to humans during subsequent blood meals.
Several diseases are associated with blacklegged ticks that feed on deer mice. These include Lyme disease (Borrelia burgdorferi), the most frequently reported tick-borne infection in the United States, along with Anaplasmosis (Anaplasma phagocytophilum) and Babesiosis (Babesia microti).
Prevention and Safety
Preventing exposure to deer mice and the pathogens they carry involves a multi-faceted approach, starting with rodent-proofing homes and other structures. Sealing entry points is a primary step, as deer mice can squeeze through openings as small as a dime. Using materials like wire mesh or steel wool for holes and cracks is more effective than expanding foam, which rodents can chew through. Keeping outdoor areas tidy by mowing grass, clearing brush, and removing clutter can also make properties less attractive to mice.
When cleaning areas where deer mice may have been present, such as sheds, cabins, or attics, specific safety measures are advised to prevent inhaling aerosolized viruses. Ventilate the space by opening doors and windows for at least 30 minutes before cleanup. Avoid dry sweeping or vacuuming, as these actions can stir up dust containing viral particles. Instead, wear protective gear, including rubber or nitrile gloves and an N95 respirator if possible.
Contaminated areas, including droppings, urine, and nesting materials, should be thoroughly wetted down with a disinfectant solution, such as a mixture of one part bleach to ten parts water, and allowed to soak for five to ten minutes. Use disposable paper towels or rags to clean up the materials, then double-bag them and dispose of them in a sealed outdoor garbage can. After cleanup, wash hands thoroughly with soap and water, even after removing gloves, to ensure proper hygiene. Reducing tick exposure, such as by using repellents and checking for ticks after spending time outdoors, further minimizes the risk of indirect pathogen transmission.