New chronic wasting disease test: Game-changer or unproven?
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When a chronic wasting disease (CWD) outbreak in a herd of captive deer in Beltrami County was discovered earlier this year, it was the result of investigators tracing a connection to potentially infected animals moved there from a Winona County farm.
That's often the case with CWD outbreaks — investigators tracing the movement of infected animals after the fact.
Chronic wasting disease is an always fatal neurodegenerative disease spread by malformed proteins, called prions, which are spread by infected animals.
As Minnesota officials work to contain the spread of CWD in deer, researchers are developing new technology that can help track the disease sooner.
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Under current regulations, the state Board of Animal Health requires testing of captive animals that die or are killed. Testing live animals with those types of tests is possible, but difficult.
That makes it hard to stop outbreaks because deer infected with CWD can spread the disease months before they appear sick.
"I think options for testing live animals would be a game-changer,” said Linda Glaser who runs the farmed cervidae program for the Board of Animal Health.
Cervids include members of the deer family such as various species of deer, elk and moose.
All are susceptible to chronic wasting disease.
"If we can test healthy, live animals, and potentially repeat that testing to monitor those animals over time, that would be a great benefit to detecting the disease," said Glaser.
Live tests available, but held up
There is a test for live animals, but there’s a dispute over whether it’s ready for deployment as a diagnostic tool.
The testing method has been around for more than a decade and is used to detect some human neurodegenerative diseases. It’s called RT-QuIC (real-time quaking-induced conversion).
The technology could be used to test animals before they are moved from one farm to another “to understand whether or not these animals are positive for CWD," said Peter Larsen, who leads a CWD research initiative at the University of Minnesota.
The test is more sensitive than the current methods being used, Larsen said, and works on a variety of materials from animal tissue to soil infected with prions.
Researchers have used the test to accurately detect chronic wasting disease in blood and fecal matter.
"So that would prevent situations like the Beltrami County case from happening, and ultimately, that would save the state millions and millions of dollars over time," said Larsen.
U of M researchers sampled bones, soil and plants at a Beltrami County site where CWD-infected deer carcasses were dumped by a farmer. They found CWD prions in all of those materials. Prions can remain infectious in the environment for years, but it’s unclear how easily they transfer from the environment to live wild animals.
Newest test is field-deployable
Over the past year, U researchers finalized a version of the test called MN-QuIC that can be used in the field without sending samples to a lab.
The portable test idea got its start about a year ago, when a student working in the lab observed that prion proteins interacted with nanoparticles.
“The solution turned red for [a] positive sample, and it was blue or purple for a negative sample,” said Larsen. “And so when we had that discovery, we knew it was important, because that put us on a path to field-deployable CWD diagnostics.”
The new field test would be cheaper and faster, he said, and makes Minnesota a leader in CWD testing technology.
In March of this year, the test was used in southeastern Minnesota — the first time a CWD test was used in the field and returned results within 24 hours, said Larsen.
But the Board of Animal Health has no immediate plans to use the test on live animals because it doesn't meet standards set by the U.S. Department of Agriculture.
The USDA coordinates with state agencies to encourage cervid owners to comply with certification program standards.
"This [RT-QuIC test] has not been validated for use in a diagnostic sort of situation,” said Glaser. “So in other words, it would have to be validated and approved by USDA to use it for that routine surveillance. And that hasn't happened yet."
The Minnesota Department of Natural Resources is taking the same position.
"There will be benefits of this RT-QuIC testing method. But we as an agency won't be using that until the USDA does validate that test," said wildlife health specialist Erik Hildebrand.
The USDA did not respond to questions about the test validation process or timeline.
Test delay frustrates some
State regulators' decision not to use the test at this time doesn't sit well with some lawmakers.
"I don't think we can wait two or three or four or five years for validation," said Rep. Rick Hansen, DFL-South St. Paul, who chairs the Minnesota House Environment and Natural Resources Finance and Policy Committee.
Hansen wants all captive cervids tested using the RT-QuIC method. He says that would provide a good assessment of the risk of CWD spreading from farmed deer to wild white-tailed deer.
Hansen says state agencies have the authority to use the test, even if it's not validated.
The language in the Board of Animal Health rules regarding testing states reads: “Other testing protocols may be used if they are approved by the board and are equally effective for the detection of CWD in farmed cervidae herds.”
Glaser argues that until the test is validated, its effectiveness is uncertain.
Larsen says he is confident the test is very effective on blood samples and tissue.
Hansen believes the test can be an early warning, preventing farmed deer from spreading CWD.
"We should use [RT-QuIC] as an indicator, and if it indicates that there's a positive, then you can follow up with a post-mortem test, if you cull that animal,” said Hansen. “I think that's a reasonable precaution to take."
Doing that testing on the approximately 8,000 farmed cervids in Minnesota would require an investment in lab equipment and training, since the state doesn't currently have a lab set up to do large-scale RT-QuIC testing.
Researchers in other states, including Wisconsin, are working to validate the RT-QuIC test, and Peter Larsen sees multiple labs focusing research on the test as concerns about CWD grow nationally.
"It's the negative impact on multiple economic sectors, and it's for protecting the heritage of deer. This is why we must improve CWD diagnostics," said Larsen.
