WILDLIFE WATCHING --  Disease that's ravaged wild sheep in parts of Washington, Idaho and Montana in recent years has shown up in one of America's most prized wildlife preserves.

A pneumonia outbreak has killed at least ten bighorn sheep near Yellowstone National Park.

Montana Fish Wildlife and Parks officials said Monday that the outbreak was in the Upper Yellowstone sheep herd near Gardiner, where bighorns are often highly visible to the public.

The dead animals include a mix of rams, lambs, and one adult ewe.

Sheep in the Gardiner area have experienced smaller pneumonia outbreaks in the past few years.

There are domestic sheep in the same area.

State officials say research has shown that bacteria can be transmitted from healthy domestic sheep to bighorn sheep, causing pneumonia in the wild sheep.

Related reading:

• Hells Canyon bighorns removed for disease study, Oct. 2014
• Washington kills last of diseased Tieton bighorns, Oct. 2013
• Killing off sick bighorns aided herds, Montana officials say, July 2011