Here & Now

Wisconsin Researcher On Rise Of Chronic Wasting Disease

ACCORDING TO THE DNR, CHRONIC WASTING DISEASE, ALWAYS FATAL TO INFECTED DEER, HAS NOW BEEN FOUND IN 18 WISCONSIN COUNTIES. BUT CURRENTLY 41 COUNTIES ARE AFFECTED BY CWD. IN THESE COUNTIES, BAITING AND FEEDING IS PROHIBITED AND THE COUNTY IS INCLUDED IF A WILD OR CAPTIVE ANIMAL HAS BEEN TESTED AND CONFIRMED TO BE POSITIVE FOR CWD OR IS WITHIN A TEN-MILE RADIUS OF AN ANIMAL CONFIRMED POSITIVE. IN ONE HOT ZONE FOR CWD IN NORTH CENTRAL IOWA COUNTY, THE PREVALENCE OF THE DISEASE IN ADULT MALE DEER IS NOW AT ABOUT 45%. THE SPREAD OF CWD IS A GROWING CONCERN FOR GOVERNOR SCOTT WALKER, WHO SAYS TESTING FOR THE DISEASE IS ON THE INCREASE.

SCOTT WALKER:

SO FAR, WE’VE TESTED MORE THAN 193,000 DEER, MORE THAN ANY OTHER STATE. WE ALSO CREATED COUNTY DEER ADVISORY COUNCILS IN EVERY COUNTY TO GIVE A VOICE TO HUNTERS, FARMERS AND FORESTERS IN THEIR HOME AREA SO WE CAN HAVE AN UNITED FRONT IN MANAGING THE STATE’S DEER POPULATION. AS A HUNTER MYSELF, I APPRECIATE THE NEED TO DO ALL WE CAN TO COMBAT CWD EFFECTIVELY. ADDITIONALLY, WE’RE WORKING IN A BIPARTISAN EFFORT TO HELP KEEP OUR HUNTERS IN THE WOODS AND PROTECT THE HEALTH OF OUR DEER POPULATION BY INVESTING IN SOUND SCIENCE, CREATING A RAPID TESTING PROTOCOL AND ESTABLISHING BEST MANAGEMENT PRACTICES FOR THE DEER FARM INDUSTRY.

FREDERICA FREYBERG:

IT SHOULD BE SAID THAT IN 2012 GOVERNOR WALKER ADOPTED A SO-CALLED PASSIVE MANAGEMENT OF CWD IN WISCONSIN AND THE EXPERT WHO ADVOCATED THAT POLICY SAYS THE DISEASE IS NOT ON THE MOVE. THE STATE IS SIMPLY SAMPLING MORE. OUR NEXT GUEST IS A SCIENTIST WITH THE U.S. GEOLOGICAL SURVEY’S NATIONAL WILDLIFE HEALTH CENTER, CWD EXPERT BRYAN RICHARDS. HE ALSO ADVISES THE STATE DNR. THANKS VERY MUCH FOR BEING HERE.

BRYAN RICHARDS:

YOU’RE WELCOME.

FREDERICA FREYBERG:

WHAT CAN YOU TELL US ABOUT THE SPREAD GEOGRAPHICALLY AND THE GROWTH AND PREVALENCE OF CWD IN WISCONSIN SINCE IT WAS FIRST ISOLATED IN THE EARLY 2000s?

BRYAN RICHARDS:

WELL, CWD– IT’S VERY CLEAR WHEN IT BECOMES ESTABLISHED IN A FREE-RANGING POPULATION WE TEND TO SEE TWO PHENOMENA. THE FIRST IS GEOGRAPHIC GROWTH AND THE SECOND IS A GROWTH IN PREVALENCE, WHERE THE PROPORTION OF ANIMALS POSITIVE. BOTH OF THESE ARE VERY CLEAR PHENOMENON WE’RE WITNESSING IN SOUTHWESTERN WISCONSIN.

FREDERICA FREYBERG:

AND HOW MUCH HAS IT GROWN? I THINK YOU HAD DESCRIBED THAT GROWTH AS UNPRECEDENTED?

BRYAN RICHARDS:

THAT’S CORRECT. THE PREVALENCE RATE WE’VE SEEN IN NORTH CENTRAL IOWA COUNTY HAS BEEN MATCHED IN OTHER GEOGRAPHIC AREAS IN THE UNITED STATES AND IN SOUTH SASKATCHEWAN BUT THE RATE AT WHICH IT GOT TO THAT HIGH PREVALENCE LEVEL IS UNPRECEDENTED IN FREE-RANGING POPULATIONS.

FREDERICA FREYBERG:

NOW, IN YOUR MIND ARE WE FINDING MORE OF IT BECAUSE WE’RE TESTING FOR IT MORE?

BRYAN RICHARDS:

I THINK QUITE THE CONTRARY. IF YOU LOOK AT THE SAMPLING DATA FROM THE STATE OF WISCONSIN, DUE TO FISCAL CONSTRAINTS, THE AMOUNT OF SAMPLING HAS GONE DOWN PRECIPITOUSLY SINCE THE DISEASE WAS FIRST DETECTED. SO WE’RE LOOKING AT FEWER ANIMALS EACH YEAR BUT FINDING THE SAME OR MORE POSITIVES EACH YEAR.

FREDERICA FREYBERG:

DO YOU THINK IF WE WERE TESTING MORE, WE’D BE FINDING IT EVEN MORE?

BRYAN RICHARDS:

ABSOLUTELY. IT’S VERY CLEAR. THE SURVEILLANCE THAT’S BEING CONDUCTED TODAY PROBABLY FINDS MAYBE IN THE REGION OF MAYBE 10%, 15%, 20% OF THE POSITIVES OUT THERE.

FREDERICA FREYBERG:

WHAT IN YOUR MIND WOULD BE THE BEST WAY TO STEM CWD IN WISCONSIN?

BRYAN RICHARDS:

THERE’S TWO CONCERNS. THE FIRST IS PROTECTING THE REGIONS OF NORTHERN WISCONSIN THAT HAVE NOT DETECTED CWD YET. AND THEN THE SECOND ISSUE IS DEALING WITH CWD WHERE IT IS. WITH REGARD TO PREVENTION, I THINK WE CAN IDENTIFY PATHWAYS, YOU KNOW, HOW CWD INFECTIOUS MATERIAL IS LIKELY TO MOVE TO THE NORTHERN PARTS OF THE STATE AND WE CAN PREVENT THOSE THROUGH GOOD EDUCATIONAL PROGRAMS AND REGULATORY MEASURES AS WELL.

FREDERICA FREYBERG:

ARE MORE PEOPLE EATING VENISON THAT MIGHT COME FROM ANIMALS POSITIVE FOR CWD?

BRYAN RICHARDS:

YES. I THINK THAT’S CLEAR AS WELL. AS DISEASE SPREADS, PREVALENCE GROWS AND DEER DENSITIES REBOUND IN THE SOUTHWESTERN PORTION OF THE STATE. IT MAKES SENSE THAT MORE PEOPLE ARE HARVESTING AND CONSUMING CWD-POSITIVE VENISON EACH YEAR.

FREDERICA FREYBERG:

SO WHAT IS KNOWN ABOUT THE DANGER OF THE SPREAD OF CWD TO HUMANS WHO MIGHT BE CONSUMING MORE AND MORE OF THIS VENISON EVERY YEAR?

BRYAN RICHARDS:

WELL, IF WE BOIL ALL THE SCIENCE THAT’S BEEN CONDUCTED DOWN, A SIMPLE WAY TO LOOK AT IT WOULD BE THAT THE RISK OF TRANSMISSION TO HUMANS IS VERY LOW, BUT IT IS NOT ZERO. RECENT RESEARCH THAT’S BEEN CONDUCTED SUGGESTED THAT OVER TIME THAT ABSOLUTE RISK CHANGES. SO NOW AS WE LOOK AT THE INCREASE IN CONSUMPTION OR EXPOSURE TO THAT CWD-POSITIVE VENISON, THAT EXPOSURE RATE IS INCREASING EXPONENTIALLY AS WELL. SO I GO BACK TO A GOOD FRIEND OF MINE WHO’S AN M.D. AND RESEARCHER IN PRION DISEASES. HE TOLD ME A LONG TIME AGO, HE SAID BRYAN, “THE CHANCES OF THIS ARE HAPPENING, BUT YOU’D HATE TO MAKE MEDICAL HISTORY.”

FREDERICA FREYBERG:

AND THE DISEASE THAT THE HUMAN WOULD GET IS CREUTZFELDT-JAKOB?

BRYAN RICHARDS:

CREUTZFELDT-JAKOB’S DISEASE IS A PRION DISEASE THAT AFFECTS HUMAN BEINGS. IF CWD WERE TO CROSS THE SPECIES BARRIER INTO A HUMAN HOST, WE DON’T KNOW EXACTLY WHAT IT WOULD LOOK LIKE, BUT IT WOULD CERTAINLY, ALMOST ASSUREDLY HAVE CHARACTERISTICS SIMILAR TO CREUTZFELDT-JAKOB DISEASE, WHICH IS A PROGRESSIVE DEMENTIA FOLLOWED BY DEATH.

FREDERICA FREYBERG:

ARE WE BEING ALARMIST EVEN TO TALK ABOUT THIS?

BRYAN RICHARDS:

I THINK IT’S REASONABLE TO TALK ABOUT IT. WE’VE SEEN OTHER DISEASES, BOVINE SPONGIFORM ENCEPHALOPATHY OR MAD COW DISEASE. INITIALLY IT WAS THOUGHT THAT IT COULD NOT CROSS OVER THE SPECIES BARRIER AND INFECT HUMANS AND NOW THE SCIENCE SUGGESTS IT HAS CROSSED OVER AND HAS CAUSED NEARLY 300 HUMAN MORTALITIES WORLDWIDE. SO THAT’S WHY WE DO THE SCIENCE. THAT’S WHY WE CONDUCT THE SCIENCE. BUT WE’LL NEVER REALLY KNOW UNLESS WE PICK IT UP IN A HUMAN HOST.

FREDERICA FREYBERG:

ALL RIGHT. BRYAN RICHARDS, THANKS VERY MUCH.

BRYAN RICHARDS:

YOU’RE VERY WELCOME.