By MEAD GRUVER Associated Press CHEYENNE, Wyo. (AP) \u2014 Environmental groups have filed a new lawsuit against the feeding of elk on a Wyoming wildlife refuge, saying the U.S. government should act sooner to curtail the practice. Workers at the National Elk Refuge in Jackson Hole put out alfalfa pellets during most winters to supplement natural forage and help elk survive until spring. The timing of feeding each year depends on the weather; elk don't get fed during mild winters or might be fed through a prolonged period of heavy or icy snow covering the vegetation they naturally eat. Hunters and guides support the feeding as a way to keep elk numbers up but others worry the practice encourages the spread of disease similar to mad cow disease in humans. A U.S. Fish and Wildlife Service plan released Dec. 31 would delay feeding each winter so that elk could gradually become accustomed to surviving without human help. The plan resulted from a lawsuit filed against the federal agency last March by the Sierra Club, National Wildlife Refuge Association and Defenders of Wildlife, which warned the feeding could encourage the spread of chronic wasting disease by artificially concentrating elk. The plan falls short by not taking effect for at least two years, the same groups argue in a new lawsuit filed Monday in U.S. District Court in Washington, D.C. \u201cThe bottom line is, we're not going to sit by and let chronic wasting disease become the new normal in Jackson Hole on the National Elk Refuge,\u201d said an attorney for the groups, Tim Preso with Earthjustice. U.S. Fish and Wildlife Service officials didn't immediately return a phone message seeking comment. Chronic wasting disease causes deer, elk, moose and other cervids to become listless and emaciated. Caused by mis-folded proteins called prions, the neurological condition is similar to mad cow disease, which afflicts cattle and humans who eat infected beef, and scrapie in sheep. Chronic wasting disease has spread to at least 24 states since its discovery at a research facility in Colorado in the late 1960s. The disease made its first appearance in Jackson Hole in 2018, when a mule deer killed on a road in Grand Teton National Park tested positive. The detection raised concern chronic wasting disease could become established in Jackson Hole and the surrounding Yellowstone-area ecosystem.