Chronic Wasting Disease study enters third year

Deer always go home for the winter. This makes life easier for Dr. Tom Hobbs and his team of Colorado State University graduate students studying Chronic Wasting Disease among deer in northern Larimer County.

In January and February, teams of researchers, wranglers and helicopter crewmen will conduct their third annual capture of deer for a five-year study. Last year they captured 190 animals for testing, including 90 that had been captured previously.

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Deer are captured on private lands, with the landowners’ permission, by helicopter wranglers using nets. The animals are transported to a field testing site where blood, urine and feces samples are taken to study genetics and other factors. The deer are then equipped with radio transmitting collars and released.

By tracking radio transmissions, the researchers can follow deer migration patterns and social groupings as well as locate the animals for recapture. The collars also allow researchers to find animals that die and determine the cause of death.

Fewer than 1 percent of the deer are lost in the capture and testing phase, according to Hobbs. The goal is to transport them no more than three miles and release them close to their home range, although ranchers near Livermore reported captures in the Owl Canyon area that did not follow those guidelines last year.

CWD is a progressive, neurodegenerative disorder, similar to bovine spongiform encephalopathy or Mad Cow Disease, caused by infectious proteins known as prions. Sick deer appear to be starving and simply waste away, hence the name.

CWD cannot be transmitted to humans, but is spread from animal to animal by saliva, feces and urine. It becomes an environmental toxin capable of persisting in the outdoor environment for a long time.

To date, the CSU researchers have found a lower incidence of the disease than previous hunter data implied. Female deer in the study area have a 6 percent chance — or one out of 16 — of becoming infected in a given year. However, a much higher percentage of males — about one out of four — catches the disease each year, because they interact with more social groups than the females.

In the coming year, 50 percent or more of infected animals will succumb.

As they weaken, these deer also have a 20 percent greater chance of dying of natural causes, chiefly predation by mountain lions. The CSU researchers are also studying the dietary effects and possibility of CWD transmission to mountain lions by feeding infected meat to two lions in captivity.

Researchers have identified two genes that determine how CWD affects individual animals. Deer carrying either gene will succumb to CWD. Yet, one gene leads to a more mild case such that deer will live longer — and can thus spread the disease further. The researchers are focusing on whether certain families of deer carry the particular genes. If so, how wildlife officials might manage these families becomes a possible outcome from the study.

The CSU study is funded by a $2.5 million grant from the National Science Foundation. More details, including a video of a deer capture can be found at