Testing of a vole (commonly called “meadow mouse”) from a die-off of rodents in the Riddle, Idaho area along Highway 51 in southern Owyhee County indicates possible plague. The public is urged to take precautions and report groups of dead rodents as this investigation continues. To date, no human cases of plague have been reported.
In May, ground squirrels in Ada County southeast of Boise tested positive for plague, and one dog, which had contact with the ground squirrels, tested likely positive for plague. Late last week, possible plague in voles was reported in an area near Highway 19, immediately west of Caldwell. Idaho Department of Fish and Game and public health officials do not believe there is any connection between these three distinct areas.
Six voles and one wild mouse from the Riddle area were tested, with one vole showing probable plague infection. “Plague is endemic to our area. With heightened awareness in the public, Idaho officials are receiving a number of reports of die-offs of rodents in southwest Idaho,” says Dr. Leslie Tengelsen, state public health veterinarian. “Not all tested rodents are positive for plague, however, people need to be vigilant and take precautions for themselves and their pets.”
Plague is a bacterial disease of mammals that can cause serious illness to people and pets if not treated quickly. Common rodents that can become infected include mice, rats, voles, chipmunks, yellow-bellied marmots (also known as rock chucks), and ground squirrels, often referred to as whistle pigs. Tree squirrels in Idaho are not known to carry plague.
People can be exposed to plague:
- From flea bites of infected fleas when pets have contact with rodents or fleas outdoors, or bring infected rodents or fleas back into the home.
- By touching or skinning infected animals such as ground squirrels, rats, and rabbits.
- By inhaling droplets from the cough of an infected person or animal, especially infected cats.
People can greatly reduce their risk of becoming infected with plague by taking simple precautions, including avoiding contact with wild rodents, their fleas and rodent carcasses. They should not feed rodents in parks, picnic or campground areas and never handle sick or dead rodents. Health officials recommend:
- See your doctor immediately about any unexplained illness involving a sudden and severe fever.
- Keep your pets from roaming and hunting voles or other rodents. Sick pets should be examined promptly by a veterinarian, especially if they may have had contact with sick or dead rodents.
- Wear gloves if you must handle dead animals and rodents.
- Use insect repellent that includes DEET to prevent flea bites.
- Talk to your veterinarian about using an appropriate flea control product on pets and treat for fleas regularly. Not all products are safe for cats, dogs or children.
- Don’t leave pet food and water where rodents or other wild animals can access them and keep pet food in rodent-proof containers
- Clean up areas near your home where rodents can live, such as woodpiles and lots with tall grasses and weeds.
- Put hay, wood, and compost piles as far as possible from your home.
Symptoms in humans include sudden onset of fever, chills, headache, weakness and fatigue. In most cases there is a painful swelling of the lymph node in the groin, armpit or neck areas. Plague symptoms in cats and dogs are fever, lethargy and loss of appetite. There may be a swelling in the lymph node under the jaw. With prompt diagnosis and appropriate antibiotic treatment, the fatality rate in people and pets can be greatly reduced. Physicians who suspect plague should report it immediately to their local public health district.
People are encouraged to avoid direct contact with dead or sick voles, or other rodents. If you find groups of dead rodents do not touch them, but report the location through the Idaho Department of Fish and Game website at: https://fishandgame.idaho.gov/content/plague .
Since 1940, only five human cases of plague have been reported in Idaho. The last two cases reported in Idaho occurred in 1991 and 1992, with both patients fully recovering.