The gradual spread of chronic wasting disease from northwest Kansas east continues at a gradual, predictable rate.
But prevalence of the disease, which is always fatal to deer, within that area has increased tremendously, according to samples tested from deer last fall and this winter.
“We had 53 positives this year and collected about 700 samples,” said Shane Hesting, Kansas Department of Wildlife, Parks and Tourism wildlife disease coordinator. “That means our sample size has gone down and our positives have gone way up.”
The results were mostly from northwest and north-central Kansas, with a few deer tested from other parts of the state that appeared to be ill.
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CWD can infect all members of the deer family, including elk and moose, but has never been spread to humans or livestock. It’s a close relative to mad-cow disease and some fear it might someday make the jump to other species.
Hesting said the previous annual high was 15 cases back in 2009, when more than 2,000 samples were taken and from most areas of the state.
CWD was first diagnosed along the Wyoming-Colorado border in the 1960s. It has spread over the past 20 years to several Canadian provinces and more than 15 states as far east as New York. Kansas’ first case was in 2005 in Cheyenne County, in the extreme northwest corner of the state, near where it had been found across the Nebraska border.
The disease has since spread to the east and south at the rate of about a county or two per year. A single positive result last fall in Jewell County, in north-central Kansas against the Nebraska border, is the easternmost case of the disease in a wild deer.
Wildlife and Parks tested deer all over Kansas for several years, but budget restrictions condensed testing different parts of Kansas are tested annually. Hesting said 40 of the diseased deer recently diagnosed were from northwest Kansas, which is roughly from Hays north and westward. The previous high for that region was 10 deer in 2010. The other 13 were from north-central Kansas.
Hesting referred to the increase in prevalence as “alarming” and said it may continue to rise at fast rates.
“The prions that spread the disease are becoming more and more prevalent now up in the area. As well as deer carrying them, they are in the soil and may even be in the dust. When the dust gets on the plant, and a deer eats that plant…,” he said. “It’s something you hope will never happen, but you aren’t real surprised when it does.”
He said it can be spread through many other ways, including if a coyote or scavenger eats portions of an infected deer’s nervous system. Though not affected by the disease, the feces of that coyote could spread more the prions to new areas. Hunters transporting diseased animals, and discarding the bones in new areas could also be contributing to the spread.
Hesting said recent research largely focused on mature bucks of at least 2 1/2 years in age because they seem more likely to carry the disease. They are often the most common kind of deer that can provide samples for taxidermists who cooperate by taking samples for the research, as do some wild game meat processors.
He estimates about 14 percent of such animals in northwest Kansas carry the disease.
Hesting said even in states with longer histories of CWD, it’s not believed the disease kills a sizable percentage of a deer population in most areas.
The exception is an area in southern Wyoming, with some of the nation’s highest CWD densities.
“Around there it sounds like you could pretty much flip a coin to decide if a deer has CWD or not, it’s that common,” he said. “That’s the only place where I know they think it’s really hurt the population, but I don’t think they’ve ever said exactly how much it has hurt.”