Conservation Wildlife Management

Rare Pneumonia Outbreak Kills 200 Pronghorn Antelope in Western Wyoming

Officials are concerned that the bacteria could spread and kill more pronghorn
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dead wyoming pronghorn pneumonia
Approximately 200 pronghorns have died from the disease so far. WGFD

The Wyoming Game and Fish Department announced Thursday that it’s investigating a rare disease outbreak that has killed roughly 200 pronghorn antelope in the state over the last several weeks. These mortalities are concentrated near Pinedale, a sparsely populated town at the base of the Wind River Mountains.

Early results from the Wyoming State Veterinary Laboratory show that a rare type of bacterial pneumonia known as Mycoplasma bovis is killing the antelope. State authorities emphasize that this is different from Mycobacterium bovis, a similarly-named bacteria that causes tuberculosis in cattle.

The pathogen is typically spread by direct contact of nasal and respiratory secretions, and it occurs globally in cattle populations, according to WGFD. Symptoms include lethargy, loss of appetite, and coughing. The disease can also affect bison, whitetail deer, and mule deer, but it has not been shown to affect domestic animals such as horses, dogs, or cats. It is not considered a human health risk, either.

A similar outbreak occurred in the northeastern part of the state in 2021, killing more than 460 pronghorns in the area. WGFD

“While reported Mycoplasma bovis outbreaks causing mortality in wildlife are rare, this is not the first occurrence of M. bovis being linked to pronghorn mortalities in Wyoming,” WGFD disease specialist Hank Edwards told the Billings Gazette.

A similar outbreak occurred during the winter of 2019 to 2020, according to the agency. That outbreak took place near Gillette and involved at least 460 animals. It started around the same time of year (in mid-February) and tapered by early April.

The disease tends to kill antelope relatively quickly, as pneumonia is often a death sentence for the critters during the harsh winter months. This comes at a time when some wildlife populations across the West have been struggling to survive an especially hard winter.

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The mass mortality event also follows a notably bad year for EHD (also known as blue tongue disease) in Wyoming, according to Cowboy State Daily. The viral disease killed a significant number of deer and antelope in the state over the course of last year. This led WGFD to cut roughly 8,000 antelope tags along with 3,300 mule deer tags for the 2022 fall hunting season.  

As of this week, WGFD staff are still removing carcasses from the Pinedale area. They will also continue to euthanize dying pronghorns to prevent further spread of the disease. It remains to be seen whether this event will have any effect on hunting license quotas this fall.