PINEDALE — The Wyoming Game and Fish Department and the Wyoming State Veterinary Laboratory are collaboratively investigating a “rare disease outbreak” in pronghorn in western Wyoming. About 200 pronghorn antelope have died since mid-February, mainly near the southern end of the Mesa south of Pinedale. Preliminary lab results identify Mycoplasma bovis as the pathogen responsible for the mortalities.

According to Game and Fish, Mycoplasma bovis should not be confused with Mycobacterium bovis, which causes tuberculosis in cattle; the two unrelated bacteria cause very different diseases.

In a March 8 release, Game and Fish explained, “The source of infection of the M. bovis and the ability to predict the duration and the geographic distribution of this outbreak in pronghorn is unknown at this time.”

“While reported M. bovis outbreaks causing mortality in wildlife are rare, this is not the first occurrence of M. Bovis being linked to pronghorn mortalities in Wyoming,” said Game and Fish Wildlife Disease Specialist Hank Edwards.

The first reported cases of pneumonia in pronghorn occurred during the winters of 2019 and 2020 near Gillette, involving at least 460 animals. Those outbreaks started at a similar time in mid-February and then tapered down by the beginning of April.

To date, this pathogen has not been shown to affect domestic pets such as horses, dogs or cats and is not considered a human health risk.

Local Game and Fish personnel advise that they are periodically removing carcasses and euthanizing dying pronghorn in relatively accessible areas when disturbance to other healthy wintering pronghorn is minimal to help reduce the prevalence of this pathogen on the landscape.

Game and Fish continues to monitor for this disease across the state.