The ongoing COVID-19 pandemic has changed the world as we know it. Chronic wasting disease (CWD) is changing the world for deer, elk and moose just as profoundly, and impacting people in less obvious ways.
Eric Seabloom and Elizabeth Borer, professors in Ecology, Evolution and Behavior, recently joined an interdisciplinary team of researchers to study CWD, a fatal neurological disease, typically killing infected animals within two years.
CWD is common in Wisconsin and is a growing concern in Minnesota where scientists are closely monitoring its arrival. The potential impact is staggering. The Minnesota Department of Natural Resources (DNR) estimates that deer hunting season generates 500 million dollars annually for the state. And deer might not be the only living thing impacted. Recent research indicates that plants can take up the CWD-causing proteins and might transmit them to animals that eat those plants. For, this reason, Norway has banned agricultural commodity imports coming from areas with CWD, and more countries may follow.
A research team, with Seabloom as the lead, recently received the 2020 Minnesota Futures Grant, offered annually by the Office of the Vice President for Research, to better understand how plants, soil, and water may contribute to CWD transmission. The team includes researchers from UMN’s College of Veterinary Medicine and the College of Food, Agricultural, and Natural Resource Sciences.
Researchers have expertise in how diseases can spread through wildlife, watersheds and plants, which will help provide a more complete picture of disease transmission. They are particularly interested in tracking potential transmission via plants. “If crops readily integrate prions into their leaves and seeds, there are major implications for the agricultural industry,” says Seabloom.
Unlike more typical infectious diseases, CWD is not caused by a virus, bacteria, or other microbe. Instead, CWD is more akin to a cancer, because the disease arises when normal cells go awry. Known as a prion disease, the disease is triggered by animals ingesting misfolded prion proteins. When these misfolded proteins enter their system, they cause other proteins to also misfold, creating a domino effect that kills cells in the nervous system.
The transmission pathway is also unique. “In some ways it is the opposite of COVID-19. The viruses responsible for infecting patients with COVID-19 don’t hang around for a long time. Prions on the other hand, persist in the environment for an extremely long time,” says Seabloom. This makes it challenging to eradicate the disease once it becomes established.
Typically deer hunters shoot a deer, take the meat, and leave the carcass in the field. If that deer is CWD-positive, the carcass could release prions into the environment that remain infectious for years. These prions may spread far beyond that site due to other scavengers, water runoff, and snowmelt. Scientists currently aren’t sure the likelihood of deer contracting CWD from environmental sources — like drinking from a stream or eating a plant containing prion, and this new work will address this knowledge gap.
Experiments kicked off in July and involve growing plants in a soil that contains prions. The researchers will then quantify how many prions end up in the plants, soil, or runoff water. This is the first in a series of experiments aimed at quantifying how readily plants take up prions and the fate of prions in the environment.
Researchers are also developing two computer models of CWD spread. One will identify areas of the state that are at higher risks of having CWD “reservoirs,” or areas of concentrated occurence of the disease. This will help the DNR prioritize containment strategies. The other model will give scientists a clearer picture of how CWD spreads and how prion diseases spread more generally.
“There’s rightfully a lot of concern about CWD impacting agricultural commodities. There is also some concern about CWD spreading beyond wildlife, because similar prion diseases have moved to humans,” says Seabloom. By gaining an insight into the intricacies of the spread, researchers hope that they can limit the spread in Minnesota and beyond. — Claire Wilson