PORTLAND — The only moose herd in Oregon appears to have doubled in size in recent years, despite deaths of the animals from a parasite.

The herd numbers about 60 animals today, compared with 30 in 2006, the Oregonian reported.
The carotid worm problem was discovered in about 2010 when biologists captured a moose in Wallowa County to fit it with a radio collar. The moose died as it was being captured, and the worms were found during a necropsy.

The worms are transmitted through horsefly bites. The parasites travel through blood vessels to the brain, sometimes triggering blindness and other problems.

The Shira’s moose in Oregon are the smallest subspecies in North America, with females weighing up to 800 pounds and males weighing up to 1,000 pounds. Alaska and Yukon moose are the largest subspecies in North America, weighing about 1,500 pounds.

The Oregon herd is found in parts of the Umatilla and Wallowa-Whitman national forests. The animals migrated into northeastern Oregon from Washington state’s Spokane-Pullman region.

Moose have been reported from time to time in this corner of Oregon. Biologists say the first recorded sighting was along the Imnaha River in 1960.