More cases followed in that hunting unit, 3F2. In recent years the disease also has been confirmed in two northwestern units, 3A1 and 3B1, and in Unit 4B in the west central part of the state, in the Badlands.

Testing of deer heads submitted by hunters during last fall’s gun season led to six more confirmed cases in 3F2 and two more in 3A1.

“Only about 15% of hunters submit heads for testing in units where CWD has been found, so the infection rate is more meaningful than the raw number of positive animals found,” Bahnson said. “Approximately 3% of harvested mule deer were infected with CWD in Unit 3F2, and roughly 2% in Unit 3A1. Our infection rate in whitetails in 3F2 was about 1%.

“Overall, we could probably live with these current infection rates long-term, but they suggest an upward trend and we’ve certainly seen an expansion in the known distribution of the disease,” Bahnson said. “We need to continue to try to limit the spread within our herds as best as we can.”