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Whiskey Mountain
Disease Testing Project
Initial Concerns


July, 2011   Dubois, Wyoming


Mycoplasma ovipneumoniae, a long, tongue-twister of a name, is a pathogen that may be causing apparently perfectly healthy lambs to die before their first birthday.

Lamb recruitment, biologist jargon for the live lamb to ewe ratio, appeared decent during the 2010 summer months. Nine ewes with six lambs were seen at Ross Lake, one of the regular summering spots. This lamb-to-ewe ratio is standard.

During summer months the newborns, mothers, yearlings and matriarchal ewes are together. Usually the mature males hang out away from the nursery bands. The symptomatic problem cough appears during weaning time for the lambs, about the same time that nursery groups join the rams. Lambs with good body condition show a persistent hacking cough. Lab analysis on euthanized ailing lambs reveals the presence of Mycoplasma, and a host of other common pathogens.

No lambs born in 2010 were observed in the Whiskey Mountain winter habitat count.

Mycoplasma is a bacterium with a twist. It has a cell membrane rather than the more common cell wall. Ordinarily, antibiotics are designed to disrupt the bacterial cell wall thus destroying the germ. However, Mycoplasma cell membranes render it resistant to those types of antibiotics.

The disease in sheep form is not transmittable to humans. The human type of Mycoplasma is difficult to cure. Ovipneumoniae is even nastier to handle. Medicating a free-range ungulate herd in adequate amounts offers little hope that the right dose will be administered. Too much is as deadly as too little.

“Mycoplasma seldom affects the adult member of the herd,” stated Greg Anderson, of the Wyoming Game & Fish Department, head of the Whiskey Basin Management Team. The threat seems to fall primarily on the lambs in “the first few months after they have been weaned.”

Because the cause of the lamb die-off has not been scientifically proven, an old strategy is being given a new purpose. In the 1980's, when the Whiskey Basin herd was the premier bighorn herd, Wyoming Game and Fish used overhead nets to trap wild sheep. The trapped bighorns were transported to other areas to reestablish or reinforce other herds. This fall the Game and Fish wants to trap as many sheep as possible. Tests given to the netted bighorns will be a blood draw, fecal sample, body condition report, and a nasal swab. After taking the samples, the sheep will be ear-tagged, and released. By analyzing the results, the Wyoming Game and Fish will be able to structure a plan to combat this disease.

The National Bighorn Sheep Center is donating funds for the lab tests done on the blood, fecal and nasal swabs, and to buy apple pulp for bait under the traps. The last three annual fund raising dinners included a 50/50 raffle to support just this type of action. The raffle has generated approximately $2,500.
(Vic Augustine, Dubois Frontier, contributed to this article)