Three apples sliced, a flake of hay -- and pellets of anti-parasitic medication.

State biologists hope that is the recipe for the success of the bighorn sheep herd in American Fork Canyon, where a deadly bacterial pneumonia has flattened the herd's growth.

In mid-January, biologists and four volunteers hiked a short way up the mountain at the entrance of American Fork Canyon and left 20 piles consisting of a flake of hay topped with three sliced apples and medication pellets. The sheep ate the apples the day they were placed on the mountain, and returned the next day to eat the hay and all the medication, said Craig Clyde, biologist with the Utah Division of Wildlife Resources.

Since January 2000, more than 60 bighorn sheep have been reintroduced into the mountains from American Fork Canyon to Provo's Rock Canyon through a joint effort between the Foundation for North American Wild Sheep, the Utah Division of Wildlife Resources, sportsmen, conservation groups and private citizens.

Because the bacterial pneumonia not only kills adult sheep but is transferred from ewes to lambs, killing the upcoming generation as well, the population has fallen, now numbering just 35-40, Clyde said.

Scientists are especially worried because the disease, which was brought to Utah by the domestic sheep of the pioneers, is part of the reason the sheep originally disappeared from local mountains, Clyde said.

Normally the bacteria live in the nasal passages of the sheep, but stress, environmental or climatic conditions cause the bacteria to migrate into the lungs of the sheep, where it causes lesions that lead to pneumonia, he said.

Once infected with high bacteria levels, bighorn sheep tend to get very sick, and they often die by late summer.

Because of the infection, "the population is not taking off," Clyde said of the sheep.

The medication program has been used successfully in other places, including Provo Canyon and in the mountains above Springville, he said. All of the sheep across the Wasatch Front were given medication when they were captured and transported, but need the medication once a year.