Wildlife biologists believe they now may know the cause of bighorn sheep die-off above Dubois
By June Bonasera, County10.com
Anderson began his presentation with an overview of the population, lamb recruitment, and disease history of the herd, which winters in the Dubois area and is a familiar site on Whiskey Mountain, just above town. Charts were presented which depicted the height of the sheep populations in 1990 and the steady decline in populations since a catastrophic all-age pneumonic die-off occurred, which has reduced the population by close to half.
In January this year, in an effort to collect data to determine the cause of the pneumonic die-off, a combination of Wyoming Game and Fish biologists and volunteers, including local Game and Fish Commissioner Richard Klouda of Lander, gathered to trap and sample the sheep herd for the first time in approximately 20 years. Blood was drawn for sampling, along with nose and throat swabs of the captured sheep.
Pathogen testing results of the January trapping, where a total of 47 bighorn sheep were captured, included the following data:
Mycoplasma ovapneumonia positive: 14 of 47 (30%)
Lambs in the trapping found to be Mycoplasma positive: 3 of 6 (50%)
Bibersteina triholosi: 46 of 47 (98%)
Pasteurella mottocida: 2 of 47 (4%)
Mannheimia aemolytica: 1 of 47 (2%) LKT+
Mannheimia glucosidal: 1 of 47 (2%) LKT+
Of the results, the Mannheimia aemolytica, leukotoxic positive sheep was the most concerning to Anderson, as that is believed to be the combination responsible for the pneumonic die-off. The Mannheimia glucosidal, leukotoxic infected sheep was also of concern, as that bacterial pathogen has unknown implications for the health of the herd.
In closing, Anderson said he was hopeful that within the next 10-15 years, an innoculation might be developed to protect the sheep against what is now believed to be the cause of the herd decline; which has been preliminarily determined to be the combination of the bacterial pathogen Mannhiemia aemolytica in conjunction with the sheep being leukotoxic posivie.
A video of the trapping effort and introduction to the herd and project background was presented to the group of 21 attendees at the annual meeting. The video may be viewed at the following link: