Wildlife biologists at the Texas Parks and Wildlife Department (TPWD) and Texas Animal Health Commission (TAHC) epidemiologists are initiating a Chronic Wasting Disease Management Plan after a two year old white-tailed captive deer confirmed positive for the deadly cervid disease last week.
The deer, originating from a breeding ranch southwest of San Antonio in Medina County, marks the first captive deer in Texas and the first white-tailed deer in the state to be confirmed with CWD.
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CWD is a member of the group of diseases called transmissible spongiform encephalopathies (TSEs). Other diseases in this group include scrapie in sheep, bovine spongiform encephalopathy (BSE or mad cow disease) in cattle, and Cruetzfeldt-Jakob disease in humans. CWD among cervids is a progressive, fatal disease that commonly results in altered behavior as a result of microscopic changes made to the brain of affected animals.
Animal health officials and TPWD biologists are concerned over the incident because the disease has the potential of spreading to native wildlife herds and could also pose serious risk to the state's captive deer population. Landowners and rural communities could also suffer serious economical losses if the disease were to spread in an uncontrolled environment.
The $10 billion-plus Texas hunting industry could suffer significant losses if the disease spreads among the state's wild deer herds.
"This is a terribly unfortunate development that we are committed to addressing as proactively, comprehensively, and expeditiously as possible. The health of our state's wild and captive deer herds, as well as affiliated hunting, wildlife, and rural based economies, are vitally important to Texas hunters, communities, and landowners," Carter Smith, TPWD Executive Director, said last week. "Working collaboratively with experts in the field we have developed protocols to address CWD, and our implementation efforts are already well under way."
Also helping in the implementation of the response is a veterinary services team from the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (USDA/APHIS/VS).
TAHC reports that part of a routine surveillance protocol for cervid breeding facilities included tissue samples taken from the suspect Medina County deer and sent to the Texas A&M Veterinary Medical Diagnostic Laboratory in College Station where testing revealed the presence of CWD. A second test was conducted by the National Veterinary Services Laboratory in Ames, Iowa, and the initial findings were confirmed on June 30.
"Our primary objectives are to determine the source of the disease and to identify other deer breeding facilities and release sites that may have received deer from affected facilities," Smith added.
Officials have taken immediate action to secure all cervids at the Medina County breeder facility. In addition, breeder facilities that have received deer from the Medina County facility or shipped deer to that facility during the last two years are under movement restrictions and cannot move or release cervids until further notice.
TPWD is also disallowing liberation of captive deer from all breeder facilities into the wild pending further review. Additional measures to minimize risk of CWD spreading into Texas' free-ranging white-tailed deer herd and to protect the captive deer breeding industry are being considered.
Since 2002, the state has conducted surveillance throughout Texas for the disease. More than 34,000 samples collected from hunter-harvested and road kill deer have been tested for CWD.
But it wasn't until 2012 that Texas became the 18th state to confirm Chronic Wasting Disease in its mule deer population after two animals tested positive for the disease in July of that year. The animals were tested as part of a regular sampling checkpoint in the Hueco Mountains in Hudspeth County in far West Texas. The check station was established after mule deer just over the Texas-New Mexico state line were reported positive in June.
Last year in April, two additional mule deer tested at a Trans Pecos roadside check station and were confirmed positive with CWD.
"We are working with experts at the local, state and federal levels, to determine the extent of this disease, and are responding appropriately to limit further transmission," said Dr. Andy Schwartz, TAHC Epidemiologist and Assistant Executive Director. "Strong public awareness and the continued support of the cervid industry are paramount to the success of controlling CWD in Texas."
Although animal health and wildlife officials cannot say how long or to what extent the disease has been present in the Medina County deer breeding facility, the breeder has had an ongoing and active CWD surveillance program in place since 2006 with no other cases reported.
The agent that causes CWD and other TSEs has not been completely characterized. However, the theory supported by most scientists is that TSE diseases are caused by proteins called prions. The exact mechanism of transmission is unclear. However, evidence suggests CWD is transmitted directly from one animal to another through saliva, feces, and urine containing abnormal prions shed in those body fluids and tissues. The species known to be susceptible to CWD are North American Elk or Wapiti, Red Deer, Mule deer, Black-Tailed Deer, White-Tailed Deer, Sika deer, and Moose.
In June 2012, USDA-APHIS published an interim final rule that established a national voluntary CWD herd certification program (HCP) as well as interstate movement requirements for farmed and captive cervids. The program’s objective is to achieve a national approach that minimizes the risk of introducing, transmitting, and spreading CWD in cervid populations.