SIOUX FALLS, S.D. (KELO) -- A winter tradition will be returning to Wind Cave National Park in January. The park will be doing an elk management program to reduce chronic wasting disease (CWD). The number of elk will be reduced to decrease the possibility of CWD in the southwestern herd, one of three herds in the park. The reduction is part of the 2009 park elk management plan. Park biologist Angela Jarding said that this herd has about 250 to 300 animals. The herd will be reduced to 230 to 270 animals, Jarding said. CWD was first detected in Wind Cave National Park in 2002, Jarding said. CWD was detected in a private herd next to the park in 1997, Jarding said. CWD is a disease in which proteins are abnormal and cause symptoms that cause death. The disease is spread through saliva, feces and others as well as through food or drinking, according to the Centers for Disease Control. Elk, deer, moose, caribou and reindeer can all get infected by CWD. Elk populations are reduced to decrease animal-to-animal contact and to maintain healthy vegetation. Symptoms include drastic weight loss, drooling and lack of fear of people and others. An elk can get infected but it may be years before they show the symptoms. "We don't see spikes in (CWD) but it's mostly seasonal (increases)," Jarding said of CWD. There is no vaccine for CWD. "Currently all that get it will die," Jarding. "Some live longer than others." The southwestern herd has an infection rate of 3%, "It's a low impact to the population growth from year to year," Jarding said. Although the third herd, or southwestern herd, is the focus of the winter reduction, the park service monitors two other herds. The park has radio-collared elk in those two northern herds, Jarding said. Those herds have been more impacted by elk, she said. "The population is maintaining, we didn't want to reduce the size," Jarding said. The park service will also do a ground count of herds during calving in the spring. The calves and other herd animals are counted, Jarding said. 2 Huron teens sentenced to 25 years for murder During the summer elk tend to "gather in the early morning and late evening...," Jarding said. Elk are more gregarious and tend to gather in groups during the winter, Jarding said. But just because the elk gather in the winter, doesn't mean the reduction is an easy task. "The elk are very educated, it's not easy," Jarding said. Program hunters can't simply approach the elk in the open. The park service has used qualified volunteer hunters to help reduce the herd. Now, only skilled park service employees cull the herd, Jarding said. The operation is set for about five weeks because park staff will need to follow and track the herd. "It's harder in a winter with no snow, we can't use tracks," Jarding said. Any downed elk is tested for CWD. Those infected are incinerated. The elk that are not infected are donated to the Pine Ridge Reservation. While only the herd in the southwest will be reduced, all the backcountry areas of the national park will be closed to hikers from Jan. 13 through Feb. 14, except on weekends and holidays. During a reduction operation, the elk tend to move north, Jarding said. It's safer for visitors and best to close all the backcountry trails during the operation, she said.