By Laura Zuckerman
(Reuters) - A mysterious die-off of more than 400 whitetail deer along a Montana river corridor has been traced to a viral hemorrhagic disease transmitted by tiny biting flies, officials said on Tuesday.
The department of Montana Fish, Wildlife and Parks last month began to receive reports of dozens of deer carcasses in wetlands along the Clark Fork River west of Missoula, alarming local residents and wildlife officials.
Testing of organ and blood samples by a state lab showed that epizootic hemorrhagic disease was behind the deaths, agency biologist Vickie Edwards said in a statement.
The outbreak marked the first time the disease, which has devastated whitetail herds in states such as Michigan, has been confirmed west of the continental divide in Montana, she said.
The virus is carried by tiny biting flies that hatch near bodies of water. It mostly affects whitetail deer and is often fatal to them, causing hemorrhaging of such organs as the heart, liver and spleen about a week after an infectious bite.
Outbreaks in whitetail deer were first documented in 1955 in New Jersey and Michigan. The virus was behind an epidemic in Michigan last year that killed nearly 15,000 whitetail deer. That compares with 300 felled by the disease the year before, according to the state Department of Natural Resources.
Humans have not been shown to be affected by the disease, which has no treatment.
(Editing by Cynthia Johnston and Steve Orlofsky)