CWD -- Could animal medicine include PMN science? Got some time on your hands, might be a good idea to get more informed about CWD…
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Chronic wasting disease (CWD) is a
prion disease that affects deer, elk, reindeer, sika deer and moose. It has been found in some areas of North America, including Canada and the United States, Norway and South Korea. It may take over a year before an infected animal develops symptoms, which can include drastic weight loss (wasting), stumbling, listlessness and other neurologic symptoms. CWD can affect animals of all ages and some infected animals may die without ever developing the disease. CWD is fatal to animals and there are no treatments or vaccines.
Since the CFIA's original CWD eradication program started in 2000, the North American CWD picture has changed dramatically. Wild and farmed cases of CWD have continued to increase despite the CFIA’s aggressive attempts to eradicate it. A significant re-occurrence rate has also been seen in Canadian herds that were previously depopulated, cleaned, decontaminated, and permitted to re-stock. This led to a program review and to the ultimate conclusion that eradication measures, using quarantines and stamping-out actions in areas where the disease is endemic in wild cervids, are both ineffective and unsustainable. Based on all available information, a decision was made to switch from an eradication policy to one of control.
The CFIA's new disease control program is based on the OIE (World Organisation for Animal Health) concept of compartmentalization. Compartmentalization identifies a group of animals having a distinct health status based on biosecurity management and husbandry practices. Herds enrolled on a VHCP and compliant at level D or higher are considered to be the compartment for CWD in Canada.
Only a few viable tools exist to deal with CWD. As a result, disease prevention is the most effective control measure. By participating in a VHCP, individual producers mitigate the risk through immaculate inventory control, rigorous herd testing, restricting herd entry to cervids at a similar or higher VHCP level, and enhanced on-farm biosecurity measures. Promoting compartmentalization in the national disease response program supports producers who are taking measures to keep CWD out of their farm.
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By Collene Ferguson, Faculty of Veterinary Medicine, U of C April 18, 2019 Cases of an infectious disease that kills deer, elk, and moose are on the rise in Alberta.
Similar to mad cow disease (BSE) in cattle, chronic wasting disease (CWD) is a prion disease of members of the deer family. Infected animals lose weight drastically (wasting), and suffer other symptoms like stumbling, lack of co-ordination, and drooling. CWD is fatal in all cases. There is no cure, treatment, or way to prevent it.
But the study of a vaccine against CWD has made researchers in the
Faculty of Veterinary Medicine (UCVM) hopeful. The study was published recently in the
Journal of Biological Chemistry. It found the vaccine, tested in a mouse model, prolonged the time before infected animals developed symptoms by up to 60 per cent.
“The vaccine doesn’t prevent the disease, but it delays its onset,” says Dr. Dalia Abdelaziz, PhD, a researcher in
Hermann Schaetzl’s lab. “And that’s what we want. In mice, if we are extending it for around 70 days that’s significant, because their life span is much shorter than deer or elk. That’s why we are excited about the results. We couldn’t induce full protection, but the survival time was greatly increased.”
Triggering an animals’ immune system to fight its own mutant proteins CWD isn’t caused by a virus or bacteria. The infective agent is a prion — an abnormal form of a harmless protein found in the brain. Once prions are present in the brain, they multiply by causing normal proteins to refold into an abnormal shape.
“The immune system of the animal doesn’t detect prions as an enemy, so there’s no immune response against the disease,” says Simrika Thapa, an
Eyes High and Killam doctoral student and co-author of the study. “We are trying to create an immunogen that induces an immune response in the animal. It’s like a flu shot producing a response so your body recognizes and defends itself against the disease.”
CWD ‘spreading like crazy’ in North America “There’s no treatment, and the other huge problem with this disease is it’s very contagious, so its spreading like crazy in North America,” says Abdelaziz. “Animals spread the infection, shedding it in their urine, saliva and feces, and the result is the infection is almost everywhere in the environment.”
“It’s not just in the animals’ brains, it’s in their muscles as well,” adds Thapa. “It’s not only in the central nervous system, it’s throughout the body. When an animal dies and decomposes in the environment, they are contaminating all the plants and the soil. So, when deer eat plants or get in contact with soil, the infectious protein gets inside the body. And the infectious protein can stay in the soil for many years.”
Does CWD pose a risk to people? There are questions about whether CWD can jump the species barrier and infect people. That’s what happened in another prion disease called variant Creutzfeldt-Jacob disease, the human form of mad cow disease.
“The potential of cross-species transmission into humans is an alarming issue and is still an open question,” says Abdelaziz. “There haven’t been any reported cases of CWD in people, but studies of squirrel monkeys have shown its transmissibility into non-human primates.” The Schaetzl lab is part of a multinational consortium studying whether CWD can infect also macaques, using transgenic mouse models as an additional read-out.
The question now is whether the vaccine is as effective in deer. As a first step, Dr. Rob McCorkell, DVM, with the help of three vet med students, did immunization studies in reindeer at UCVM’s Spy Hill campus.
“Our next step is to work on an oral vaccine that can be used in wildlife. You can’t vaccinate free-ranging deer by injection, so we are considering plant-based vaccines that can be eaten directly by deer and elk,” says Abdelaziz. “We are working on arranging collaborations with other facilities where it is possible to immunize and then infect with CWD, to test in the real host.”
“We have lots of future directions in this project, and we are so excited.”
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June 22. 2019
Canadians are being warned about the spread of a deadly animal disease that has the potential to infect humans especially after some of the animals were released for human consumption.
Chronic wasting disease (CWD) is similar to mad cow disease (formally known as bovine spongiform encephalopathy or BSE). It infects deer, elk, and moose and it's spread by a protein — called a prion — which has the unusual ability to spread between animals causing a deadly wasting disease.
There is no direct evidence that it can spread to humans, but recent research showing transmission to non-human primates (macaques) has heightened concerns.
Until last fall, CWD had only shown up in wild and farmed deer and elk in Alberta and Saskatchewan.
But in September 2018, a deer farm in Quebec had a major outbreak; 2,788 animals were destroyed and 11 animals were found to have been infected.
According to the
Canadian Food Inspection Agency, the rest of the animals that tested negative, along with younger animals under 12 months — 2,777 deer — were released for human consumption, a decision that remains controversial.
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Dr. Neil Cashman was one of the signatories. He's a professor at the Faculty of Medicine at the University of British Columbia and has researched prion diseases for over 20 years.
"I think CWD has the possibility of having more negative impact for Canada and its economy then did … mad cow disease," he said. "I think we're teetering on the edge of a catastrophe."
The directives listed in the letter include:
- Contain the geographic spread of CWD, for example, by banning the movement of deer, and potentially infected carcasses.
- Prevent human exposure.
- Fund independent, evidence-based initiatives to prevent the transfer of CWD via food and feed chains.
"I think the Canadian consumer should be very worried," Cashman said. "The problem is the positive carcasses are being consumed all the time, with no knowledge, and no planning about how to reduce this risk."
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PrioNet Canada teams up scientists with industry partners to conduct cutting-edge research
Vancouver, BC - Several Canadian researchers have come together to help control the relentless spread of a prion disease, chronic wasting disease (CWD) in deer and elk, through vaccines. At the same time they aim to generate safe and effective therapies for common cancers. This simultaneous research is possible thanks to a unique connection they have discovered between the two unrelated diseases.
The project builds on links between prion proteins present in certain prion diseases like CWD in animals and common cancers in people like melanoma and lymphoma. The multi-provincial research is made possible by Vancouver-based PrioNet Canada's Bootstrap program and involves three scientists along with two industry partners, Toronto-based Amorfix Life Sciences Ltd. and Saskatoon-based PREVENT - the Pan Provincial Vaccine Initiative.
https://www.vchri.ca/media-release/articles/2010/07/26/canadian-researchers-testing-unique-vaccines-prion-diseases