Shrews are small, often mouse-like mammals belonging to the order Eulipotyphla, which distinguishes them from true rodents. These insectivores are known for their high metabolism and long, pointed snouts, and they exist across a wide range of global environments. Shrews can harbor and transmit various pathogens to humans and domestic animals. They function as natural reservoirs for numerous viruses and bacteria, which can be shared with other species due to the close proximity of their habitats to human settlements.
Major Pathogens Associated with Shrews
Shrews are documented carriers for several pathogens that pose risks to human health, acting as reservoirs without necessarily showing symptoms themselves. One concern is the presence of Hantavirus strains, such as the Seewis or Asikkala viruses, which are distinct from the types carried by rodents but are still found in certain shrew species. These viruses can cause severe illness in humans and are shed through the animal’s waste products, including urine and feces. Another serious illness linked to shrews is Borna Disease Virus 1 (BoDV-1), which can cause fatal neurological inflammation, or encephalitis, in humans and livestock.
Shrews also play a role in the transmission of bacterial diseases, including Leptospirosis. This bacterial infection can lead to symptoms ranging from mild flu-like illness to severe conditions like Weil’s disease, involving kidney and liver failure. Beyond direct bacterial or viral carriage, shrews are hosts for various ectoparasites, such as ticks and fleas, which are known vectors for other human illnesses. For example, short-tailed shrews have been identified as competent reservoirs for the agents that cause Lyme disease and human babesiosis.
Transmission Methods to Humans
The exchange of pathogens from shrews to humans typically occurs through three main pathways: environmental contamination, indirect vector transmission, and, rarely, direct contact. Environmental contamination is a major route, particularly when shrew droppings and urine dry out and become aerosolized. When humans disturb contaminated areas, such as sheds, garages, or crawl spaces, they can inhale the airborne particles containing viruses like Hantavirus. This is a primary concern during the cleanup of enclosed spaces.
Indirect transmission through arthropod vectors is another common method, where the shrew acts as a host to an intermediate carrier. Ticks, mites, and fleas feed on shrews, acquiring bacterial or protozoan pathogens like the agents for Lyme disease or babesiosis. If these infected parasites then detach from the shrew and subsequently bite a human, the illness can be transferred without any direct human-shrew interaction. Shrews have also been implicated as reservoir hosts for Powassan virus, a serious tick-borne illness.
Direct contact is a less frequent but still possible route, usually involving handling an infected shrew or its carcass. Though shrews are generally non-aggressive, they will bite if threatened. Direct handling of an infected animal, or a pet bringing an infected shrew into the home, can facilitate the transfer of pathogens like Borna disease virus.
Practical Steps for Hazard Mitigation
Mitigating the hazard posed by shrews involves proactive measures to exclude them from human spaces and strict protocols for cleaning up areas they have contaminated. Prevention starts with exclusion techniques, such as sealing any cracks, gaps, or crevices in a home’s foundation or exterior walls that could allow entry. Because shrews are small, even tiny openings must be addressed to prevent them from accessing indoor areas like basements and garages.
Managing the surrounding landscape is also an important preventative step, as shrews are attracted to cluttered areas offering shelter and food sources. Removing overgrown shrubs, woodpiles, and debris near the home reduces potential nesting sites and foraging cover. Eliminating outdoor food sources like spilled bird seed, pet food, and fallen fruit discourages shrews from settling on the property.
When dealing with areas where shrew activity is suspected, safe handling and cleanup procedures are necessary to avoid inhaling aerosolized pathogens. Never sweep or vacuum dry droppings, as this can release contaminated dust into the air. The area should first be thoroughly ventilated for at least 30 minutes before beginning any cleanup. Anyone cleaning up shrew waste should wear gloves, and the contaminated surfaces should be saturated with a disinfectant solution, such as a mixture of bleach and water, allowing it to soak for several minutes before wiping it up.