Project Results

I am excited to share my findings! 

The bacterium Mycoplasma bovis (M. bovis) is a globally distributed, economically important bacterial pathogen of cattle (Bos taurus) and American bison (Bison bison). Pneumonia, polyarthritis and mastitis are among the most common clinical signs. Reports of M. bovis in free-ranging wildlife are rare, consisting of a few isolated cases in mule deer (Odocoileus hemionus) and white-tailed deer (Odocoileus virginianus). In early 2019 near Gillette, Wyoming, we documented M. bovis as the cause of acute, fatal pneumonia in free-ranging pronghorn antelope (Antilocapra americana), a previously unreported finding. Here we report on additional pronghorn mortalities due to M. bovis occurring in the same geographic region one year later. Mortalities occurred between February and April in 2019 and 2020 with over 500 documented mortalities in total. To evaluate whether pronghorn develop chronic, subclinical infections and begin assessing M. bovis status in other sympatric species, we used PCR testing of nasal swabs to opportunistically survey select free-ranging ungulates. We found no evidence of subclinical infections in 230 pronghorn sampled from nine counties in Wyoming and ten in Montana, USA. All mule deer (n=231) sampled from 11 counties in Wyoming also were PCR negative. To estimate the potential for environmental transmission, we examined persistence of M. bovis in various substrates and conditions. Controlled experiments revealed that M. bovis can remain viable for 6 hours following inoculation of shaded water, and up to 3 hours in shaded hay and topsoil. Our results indicate transmission of M. bovis from livestock to pronghorn through the environment is possible, and that seasonality of infection could be due to shared resources during late winter. Further investigations to better understand transmission dynamics, to assess population level impacts to pronghorn, and to determine disease risks among pronghorn and other ungulate taxa appear warranted.

Link to published paper.

About This Project

Mycoplasma bovis (M. bovis) is an economically important bacterial pathogen of cattle. We recently documented seasonal occurence of M. bovis in pronghorn antelope in northeast Wyoming in 2019 and 2020, resulting in over 500 mortalities. Through targeted surveillance, we aim to determine if exposed pronghorn serve as carriers of M. bovis that pose a transmission risk to naive wildlife and livestock. We expect to find reservoir pronghorn in the previously exposed population.

Ask the Scientists

What is the context of this research?

M. bovis contributes to polymicrobial bovine respiratory disease and has a large economic impact on cattle producers. Historically limited to cattle, the host range of M. bovis has more recently expanded to include ranched bison, in which the bacterium is highly pathogenic. Prior to our recent identification of M. bovis in a pronghorn herd experiencing outbreaks of fibrinous pleuropneumonia, the bacterium had not been reported in this species. The seasonal reemergence of M. bovis in the same pronghorn herd suggests either a repeat spillover event from cattle, or infection of naïve pronghorn by animals that survived the 2019 outbreak and served as asymptomatic carriers.

What is the significance of this project?

Pronghorn are a unique and iconic, native wildlife species in Wyoming. Their geographic range is limited to the Great Plains, and they are sensitive to land development and other anthropogenic habitat disturbances. Traditionally, pronghorn are not considered a major threat to the health of cattle or bison, and they are widely tolerated on commercial operations. Our recent observations support the emergence of M. bovis as an important wildlife-livestock interface disease. Currently localized to one region of Wyoming, this disease has shown potential for rapid spread. This study is relevant to livestock producers, biologists, veterinarians, conservation scientists, and stakeholders who value a better understanding of transmission risk.

What are the goals of the project?

The main goal of this project is to better understand how and why fatal M. bovis outbreaks occurred in pronghorn in a focal region of Wyoming during the spring season for two consecutive years. To better understand transmission dynamics and risk, we aim to determine if asymptomatic pronghorn can serve as a reservoir of M. bovis, potentially contributing to epizootics and/or posing a risk of spillover to other species. If we find that previously infected pronghorn become chronic carriers, this could promote geographic expansion to other herds, as well as additional seasonal die-offs as new animals join the previously affected herd. The analysis of our results here can be used to inform wildlife management and thereby minimize transmission risk.