Wildlife biologists from Idaho, Washington, and Oregon next week plan to
capture bighorn sheep in the tri-state Hells Canyon area to give them an experimental
vaccine that they hope will protect them from a fatal disease.
In December 1995, more than 100 bighorns along the Snake River in southeast
Washington, northeast Oregon, and west-central Idaho died from a pneumonia-like
disease caused by Pasteurella spp. bacterias that produce toxins deadly to wild sheep.
In an interagency effort funded by the private, non-profit Foundation for North American
Wild Sheep (FNAWS), 72 sheep were captured along the Washington side of the
Snake River and transported to a wildlife health lab in Idaho for treatment. Only eight of
those sheep survived.
Next week's experiment is designed to vaccinate ewes to prevent them from
passing the Pasteurella bacteria that they may be carrying to their lambs. Like most
mother mammals, a ewe's milk provides immunities from disease to the newborn lamb.
But that protection wanes after a few months and the young sheep can be vulnerable to
disease. The experimental vaccine might offset the chance of disease spread.
The project plan calls for capturing 36 adult bighorn ewes, 12 each from the
Idaho's Redbird, Washington's Black Butte, and Oregon's Wenaha herds. Half will be
randomly selected to receive the vaccine. All of the sheep will be equipped with radio
telemetry collars so that they and the lambs they give birth to in May can be tracked
regularly. Effectiveness of the vaccine should be determined this fall by overall lamb
survival. The vaccine will also be tested on the eight sheep still in captivity at the Idaho
FNAWS again will help foot the bill for helicopter capture of the sheep. The
organization has pledged that recovery of Hells Canyon bighorn sheep is its number
one priority. The vaccine experiment will be one step towards such recovery.