Ohio negative for CWD again
It is a good thing that Ohio’s wild deer so far apparently are not infected with the dreaded, deadly chronic wasting disease, or CWD, as recently reported by the Ohio Division of Wildlife and state agriculture authorities.
But the fact that no confirmed CWD cases have turned up among thousands of deer sampled here since 2002 is no cause for celebration. It is just another bullet dodged. CWD now infects deer in 22 states and two Canadian provinces, including neighboring Michigan, Pennsylvania, and West Virginia.
What is new and chilling in the long-standing CWD menace is a warning from the U.S. Centers for Disease Control in Atlanta. The abstract of a recent CDC advisory is worth quoting at length:
“Although detection in some areas may be related to increased surveillance, introduction of CWD due to translocation or natural migration of animals may account for some new foci of infection. Increasing spread of CWD has raised concerns about the potential for increasing human exposure to the CWD agent.
“The foodborne transmission of bovine spongiform encephalopathy to humans indicates that the species barrier may not completely protect humans from animal prion diseases (emphasis mine). Conversion of human prion protein by CWD-associated prions has been demonstrated in an in-vitro cell-free experiment, but limited investigations have not identified strong evidence for CWD transmission to humans. More epidemiologic and laboratory studies are needed to monitor the possibility of such transmissions.
So, the best science can tell us right now is that the question of CWD infecting humans is hardly a closed case. Which is why I stress the need to avoid smugness about CWD.
In Ohio state and federal agriculture and wildlife officials collected tissue samples from 753 deer killed on roads from last September through March. An additional 88 hunter-harvested mature bucks and nine deer displaying symptoms consistent with CWD were tested as well. All samples tested negative for CWD.
But the state of Missouri, where CWD was confirmed in 2010 and 2011 in captive deer herds in big-game hunting preserves (a classic culprit in CWD spread), is going all out now to protect its deer hunting industry. Since the captive outbreak another 10 free-ranging wild deer have been confirmed with CWD in a limited north-central region. Again, typical. It is what Ohio could face should CWD rear its ugly head here.
Some telling CWD snippets from the Missouri Department of Conservation:
CWD is spread both directly from deer to deer and indirectly to deer from infected soil and other surfaces. Animals with signs of CWD show changes in natural behavior and can exhibit extreme weight loss, excessive salivation, stumbling, and tremors. CWD in deer can only be confirmed by laboratory tests of brain stem or lymph tissue from harvested animals.
There is no scientific evidence that white-tailed deer have a genetic immunity to CWD that could be passed on to future generations.
Once well established in an area, CWD is impossible to eradicate. States with CWD must focus on limiting the spread of the disease and preventing its introduction to new areas.
The disease has no vaccine or cure. CWD is 100-percent fatal. Deer and other cervids can have CWD for several years without showing any symptoms. Once symptoms are visible, infected animals typically die within one or two months.
People often mistake for CWD hemorrhagic disease, or HD, which includes both bluetongue virus and epizootic hemorrhagic disease (EHD) virus. During the summer and fall of 2012, severe drought conditions contributed to a significant increase in cases of HD throughout Missouri. The naturally occurring viruses are spread by a small, biting midge fly during the summer and fall. Disease outbreaks end when cold weather kills the host flies. Deer typically show symptoms within days of being infected, and not all infected deer die from HD.
MDC has placed a restriction on activities that are likely to unnaturally concentrate white-tailed deer and promote the spread of CWD, including a ban on the placement of grain, salt products, minerals, and other consumable natural or manufactured products in its CWD Containment Zone.
MDC also has rescinded the antler-point restriction (four-point rule) in the CWD Containment Zone because antler-point restrictions protect yearling males and promote older bucks. Yearling and adult male deer have been found to exhibit CWD at much higher rates than yearling and adult females, so a reduction in the number of male deer can help limit the spread of CWD. The dispersal of yearling males from their natal or birth range in search of territory and mates is also one of the primary ways CWD spreads.
The foregoing items provide a lot of food for thought here in the Buckeye State. Last and not least a summary from Missouri about the size of the stakes:
“Infectious diseases such as chronic wasting disease (CWD) threaten Missouri deer, Missouri's nearly 520,000 deer hunters, millions of wildlife watchers, thousands of landowners, 12,000 Missouri jobs, and hundreds of businesses and communities that depend on the $1 billion boost in economic activity related to deer hunting and watching.”