The Missouri Department of Conservation (MDC) received final test results today from 656 tissue samples taken from free-ranging deer harvested earlier this year. Results included three CWD-positives with two from adult does and one from an adult buck. The testing was conducted by MDC staff and area landowners in a 163-square mile area in northeast Linn and northwest Macon counties specifically for CWD sampling.
Missouri’s first two cases of CWD in free-ranging deer were detected in two adult bucks harvested in northwest Macon County during the 2011 fall firearms deer season. The three most recent CWD positives were harvested within two miles of the two original cases of CWD.
MDC conducted its 2011 fall tissue-sampling effort in response to two cases of CWD found in captive white-tailed deer at two private, captive-hunting preserves in Macon and Linn counties. Since October 2011, three more captive deer at the Macon County preserve have tested positive for CWD. Depopulation, quarantine and other management activities at the private preserve are being coordinated by the Missouri Department of Agriculture. The five cases of CWD in free-ranging deer have been found within two miles of the Macon County preserve.
While MDC identified the first case of CWD in free-ranging deer in Missouri in January, the Department has been testing for it for years. With the help of hunters, MDC has tested more than 34,000 free-ranging deer for CWD from all parts of the state since 2002.
MDC staff are further analyzing recent test results, continuing to evaluate efforts and lessons learned from other states with CWD, and consulting with various other wildlife experts around the country. The Department’s main objectives are to limit the prevalence and restrict the spread of CWD in Missouri.
According to MDC Deer Biologist Jason Sumners, there are several main factors associated with the management of free-ranging deer that will influence the future prevalence and distribution of CWD in Missouri: local deer density, deer concentration, the movement of deer and the movement of deer carcasses.
“Yearling and adult male deer have been found to exhibit CWD at a much higher rate than yearling and adult females,” Sumners said. “Of the 10 cases of CWD identified in both captive and free-ranging deer in Missouri, eight have been in adult bucks. Additionally, dispersal of yearling males from the range where they were born is one of the most likely means of expanding the distribution of CWD. The movement of infectious materials in the form of hunter-harvested deer carcasses that contain heads and spinal columns, where the disease concentrates, may also serve as a means of introducing CWD to other regions of the state.”
Sumners added that CWD has been found in only one small pocket of the state. “Our management efforts will focus on minimizing the prevalence and preventing the further spread of the disease from the area. We will keep the public informed as we develop those efforts.”
CWD is a neurological disease that is limited to deer, elk, moose and other members of the deer family, known as “cervids.” CWD can only be confirmed in deer by laboratory testing of the brain stem or lymph tissue. CWD is transmitted through prions, which are abnormal proteins that attack the nervous systems of these species. These prionsaccumulate in the brain, spinal cord, eyes, spleen, and lymph nodes of infected animals. CWD is spread by animal-to-animal contact or by animal contact with soil that contains prions from urine, feces or the decomposition of an infected animal.
Deer and other cervids with signs of CWD show changes in natural behavior and can exhibit extreme weight loss, excessive salivation, stumbling and tremors. CWD can be present in and transmitted by infected animals for up to several years before symptoms of the disease appear.
“Most deer that test positive for CWD appear to be healthy,” Sumners said. “Although one of the free-ranging does that tested positive for CWD did exhibit clinical signs of the disease.”
The Missouri Department of Agriculture (MDA) says there is no evidence from existing research that CWD can spread to domestic livestock, such as sheep or cattle. The Missouri Department of Health and Senior Services (MDHSS) says there is no scientific evidence that CWD is transmissible to humans through contact with or the consumption of deer meat.
The disease was first recognized in 1967 in captive mule deer in Colorado. CWD has been documented in both captive and free-ranging deer in Missouri, along with neighboring Kansas and Nebraska. It has been documented in free-ranging deer in neighboring Illinois, and in captive elk in neighboring Oklahoma. CWD has also been documented in both captive and free-ranging members of the deer-family in Colorado, Minnesota, New York, South Dakota, Wisconsin and the Canadian provinces of Alberta and Saskatchewan. Maryland, New Mexico, North Dakota, Utah, Virginia, West Virginia and Wyoming also have documented cases of CWD in free-ranging members of the deer family. Michigan and Montana have documented cases of CWD in captive members of the deer family.