And it's killing hundreds of ducks.
The Idaho Fish and Game says an outbreak of botulism at the Fort Boise Wildlife Management Area has killed more than 600 mallards and other waterfowl in the past several weeks.
Officers have been disposing the carcasses in an effort to stop the outbreak.
"The good news is, we've seen no dead ducks in the last 10 days, so it appears the botulism has run its course," said Andy Ogden, Fish and Game habitat biologist. "The bad news is, the outbreak killed considerable numbers of local ducks, and these are normally the birds harvested in the first few days of the waterfowl season."
The Fort Boise Wildlife area is a popular hunting spot for local hunters. The disease poses no threat to humans.
Avian botulism is found throughout the environment, Idaho Fish and Game said in a news release, with outbreaks occurring when ducks become concentrated, as occurs in the fall when waterfowl stage in certain areas before beginning their migration travels.