By Don “Doc” Sanders
I can still remember as a 12-year-old seeing live deer for the first time, in the field near my childhood home in Auglaize County. With his Super-8 movie camera my uncle captured four deer jumping a fence after they scouted the field for several minutes. It was an awesome experience for our whole family; none of us had ever seen deer in the wild.
Fast forward to today: We see deer everywhere. We also see the consequences of their presence, like damaged crops, deer-vehicle collisions and trampled flower beds. Deer seem to take a special liking to the security of residential areas, within city limits, safe from hunters. As a plus for the city deer, some people delight in putting out food, apparently in case the moochers are still hungry after plundering their neighbors’ gardens.
With deer as plentiful as they are, we’re constantly on edge as we drive on highways and country roads, especially at dusk, fearful one might run out at any moment into our path or the side of our car or truck. The deer are probably on edge, too.
Now they have an additional concern, besides becoming roadkill or getting bagged by a hunter: chronic wasting disease, or CWD. With CWD, as the disease’s name implies, an infected deer’s musculature and flesh waste away over time until the animal dies from emaciation.
But CWD isn’t just another infection like Strep, Staph or E. coli. CWD is believed to be caused by abnormally folded brain proteins called prions.
Scientists are still trying to learn why brain proteins become misfolded, but they recently learned that copper ions bind to the tail of prion proteins. They don’t know how copper binding causes the misfolding, but they do know that it seems to lead to misfolding of proteins in adjacent brain cells, which clump together.
These clumped, misfolded brain proteins become dangerous pathogens that lead to widespread destruction of an infected brain.
Prion diseases are categorized, as a group, as transmissible spongiform encephalopathy (TSE). TSE diseases are known by different names in different species — Creutzfeldt-Jakob disease in humans, scrapie in sheep and mad cow disease in cattle (so called due to the bizarre, aggressive behavior of infected cows that endangers caretakers). By the way, cannibalistic tribes in New Guinea also have a TSE disease known commonly as kuru, which spreads when people eat the brains of misfolded-prion-infected dead family members. It appears that all TSE diseases are spread by consuming infected brain tissue or by inheriting it from the dam.
Hot off the press while I was writing this column a scientific report published by Texas Life Sciences, Colorado State and the USDA has reported that the CWD misfolded prions to also occur in deer semen and other reproductive organs. Researchers aren’t certain, but believe there may also be other causes.
There is some evidence that Alzheimer’s disease has prion-like lesions similar to those in CWD and mad cow disease. In Alzheimer’s, amyloid beta proteins malform and clump together in the brain. This suggests a link to prion diseases in animals — more than previously speculated — though amyloid beta proteins are different than prions.
Mad cow disease became epidemic in Britain during the ‘90s when carcasses of sheep that died from scrapie were processed into a protein source for cattle feed. At one point, Britain had 800,000 cases of mad cow disease, apparently as a result of this. Mad cow disease disappeared gradually in Britain once the cause was discovered and the processing of scrapie-infected sheep was stopped.
To prevent the spread of TSE diseases, packing plants under state or USDA inspection are required to remove brain and nerve tissue from food animal sources. Custom slaughter plants that process meat for individual customers must also follow inspection guidelines established by state veterinary and agricultural officials.
And to prevent the spread of CWD, Ohio state laws require that deer killed during a hunting season must have the head submitted for testing, to check for misfolded prions before the meat is processed. Checking for misfolded prions in the brain stem and mandibular lymph nodes is a reliable method for determining if a deer has CWD. Any deer carcass testing positive is immediately destroyed.
Ohio’s regulations require testing of any bagged deer a year old or older but will test younger harvested deer when requested. Ohio officials report that no deer have tested positive in the past few years. Prior to this, in 2014 multiple cases were diagnosed in one herd on a private Ohio deer farm. That herd was immediately destroyed. And several years ago, individual deer on three private farms tested positive. There have not been positive cases reported for CWD in deer since then.
CWD-infected deer have also been reported being harvested in the wild in Minnesota, Wisconsin, Pennsylvania and Indiana. We are living in an interesting new era as scientists work to discover the cause of all prion diseases, CWD included.
And even more hopeful for us humans are scientists’ continuing efforts to determine the causes of Alzheimer’s and dementia, to identify ways to prevent and treat this brain pathology.