Scientists fear the deaths might be related to a plunge in moose populations in western Wyoming, where a deadly parasite was recently discovered.

PORTLAND — Oregon state biologists are planning to put radio collars on several moose this month in hopes of learning what caused the mysterious deaths of two moose.

Scientists fear the deaths might be related to a plunge in moose populations in western Wyoming, where a deadly parasite was recently discovered.

"We lost two of our radioed animals this summer, and we could never determine the cause of death," said Pat Matthews, an Oregon Department of Fish and Wildlife biologist. "So this sort of jumped out as a possibility."

A parasite could endanger Oregon's small moose numbers, estimated at 40 to 60 elusive Shiras moose. The animals migrated from Washington in the early 1990s.

The Oregon moose were wearing global-positioning-system collars when they died, Matthews said. They had been roaming the boundary of the Wenaha-Tucannon Wilderness.

A carotid artery worm, Elaephora schneideri, was isolated three years ago in the Wyoming moose and is among the suspected culprits in the deaths.

The parasite might have played a role in the decline of a Jackson Hole, Wyo., moose herd, said Wyoming biologist Steve Kilpatrick. In 1995, 4,000 animals were counted, but the numbers fell to 1,691 in the most recent count.

An examination of 69 moose carcasses in the early 1970s detected no carotid worms, according to Kilpatrick, a Wyoming Game and Fish Department biologist and chairman of the state's Moose Working Group. A similar check of hunter-killed moose last fall found almost half were infected.

Biologists suspect an ongoing drought in Wyoming, predation by bears and wolves, and the loss of cover and summer shade because of huge wildfires also may have played roles.

Carotid worms are believed to spread in the larval stage by horse flies, according to Kilpatrick. Larvae are carried into the carotid artery, where they develop into adult worms that coil in blood vessels and can block flows to the optic nerve, ears or brain.

There's no hard evidence that Oregon's moose have carotid worms because there's no way to test a living animal, Matthews said. Helicopters and net guns will be used to capture and collar several moose so biologists can test for the parasite if another collared moose dies, he said.

"This summer, we didn't know to look for it," he said.

Matthews said biologists have noticed Oregon moose with "cropped" ears, one symptom of the parasite. The condition occurs when worms obstruct blood flow, causing ear tips to freeze and fall off in cold weather.