South central Montana is experiencing a widespread outbreak of hemorrhagic diseases that are killing white-tailed deer, antelope and possibly elk.
Montana Fish, Wildlife and Parks wildlife biologists say the naturally occurring diseases are more widespread than they have seen before, but are not particularly intense in any one area.
Bluetongue disease has been confirmed in both an antelope and a white-tailed deer in the area between Hardin and Custer.
FWP has fielded reports of dead elk in that area, but have not been able to collect a carcass that is fresh enough to test.
Biologists also suspect that epizootic hemorrhagic disease, or EHD, may be responsible for some white-tailed deer deaths.
Reports of dead white-tailed deer and antelope are widespread across the region, including farther west and south than have been seen before. Biologists have fielded reports of dead animals along the Yellowstone River as far upstream as Springdale, along Rock Creek as high as Boyd, along the Stillwater River to Absarokee and along the Clarks Fork of the Yellowstone to the Wyoming state line.
Bluetongue and EHD generally infect less than a quarter of local deer and antelope populations. Biologists do not know how many animals have died from hemorrhagic diseases this fall in south central Montana.
But they do not believe the mortalities are intense in any particular area.
Both EHD and bluetongue are naturally occurring viruses spread by tiny biting midges. The virus causes bleeding that kills the infected animal within a day or two. Dead animals frequently are found near water, where they go to alleviate a high fever caused by the disease.
Symptoms of EHD and bluetongue are identical, so laboratory tests on tissue from fresh carcasses are needed to differentiate between them.
The biting midges, also called sand gnats or no-see-ums, reproduce in wet sand or mud. Their numbers peak from mid-August through October, which accounts for the season appearance of hemorrhagic diseases.
The first frost of the fall stops the midges and brings a sudden end to outbreaks of bluetongue and EHD.
Other parts of Montana, including the eastern half of the state and the Missoula Valley, have reported outbreaks of EHD this late summer.
Humans are not at risk of contracting the disease by handling or eating deer or antelope or being bitten by midges. Animals that develop infections secondary to the hemorrhagic diseases may not be suitable for consumption, however.
A brochure of additional scientific information about hemorrhagic diseases is available online from the Southeastern Cooperative Wildlife Disease Study at http://vet.uga.edu/population_health_files/HD-brochure-web.pdf.