KPC
CHRONIC WASTING DISEASE - NORTH AMERICA (02): MODE OF SPREAD ************************************************************ A ProMED-mail post
Date: 17 Jan 2020 Source: CIDRAP [edited]
A new study was the 1st to find in vitro evidence of chronic wasting disease (CWD) in samples of deer semen, the kind typically used for breeding purposes on deer farms. The study was published in PLOS One.
Tracy Nichols, PhD, an author of the study and a cervid health specialist staff officer with the United States Department of Agriculture (USDA), said the findings will not provoke a change in policy at this time. Instead they offer a necessary starting point in investigations concerning the transmission route of CWD, a fatal prion disease that affects cervids, members of the deer family.
"We need to know what the risk actually is, and if sexual transmission can occur," Nichols said. "We need someone to do artificial and natural pathway testing to get to the bottom of that question."
The current study tested reproductive tissue from 21 white-tailed deer (WTD) bucks, including semen, testes stroma, and epididymis samples. Using an amplification assay, researchers tested for CWD prions, and evidence of CWD was seen in 9 of the animals who had known CWN infections.
"The data indicate the presence of CWD prions in male sexual organs and fluids is prevalent in late stage, pre-clinical, CWD-infected WTD (80-100 percent of the animals depending on the sample type analyzed)," the authors said. "Our findings reveal the presence of CWD prions in semen and sexual tissues of prion infected WTD bucks."
In about half of the 9 positive specimens, the prions were in early stages, said Rodrigo Morales, PhD, of The University of Texas Health Science Center at Houston. Morales is a co-author of the study. This means if CWD is transmitted sexually, it could be done before an animal shows outward signs of the disease.
"We don't know at what level the prions could be transmitted, if they are transmitted sexually," said Morales.
CWD is always fatal in cervids, and in the later stages produces notable symptoms, including stumbling, drooling, and a lack of fear of humans.
Morales also pointed out CWD may be so infectious, sexual transmission may be a moot point.
"Animals in the same pen may be transmitting to each other; 2 females in the same pen could be transmitting to each other," he said. [While deer may be social animals, keep in mind, there is currently no proof of this conjecture. - Mod.TG]
Nichols explained deer are remarkable social animals. "They lick each other, they go nose to nose," she said. She also said they regularly consume soil via grazing. CWD prions have been detected in soil, in animal urine, and in the carcasses of dead animals.
Morales said he was interested in breeding studies, which would show whether a female deer's vaginal secretions can protect, or play host, to CWD prions.
Mark Zabel, PhD, the associate director of the Prion Research Center, Colorado State University, said he was not surprised by the findings, and though intriguing, said it was too premature to draw conclusions from the study.
"We know almost nothing about sexual transmission and prion diseases," said Zabel.
Scrapie, a prion disease affecting sheep, was also found to exist in sheep semen, Zabel said, but it was never determined whether the prions were passed during sexual intercourse.
For deer breeders, who can pay thousands of dollars for a single straw of deer semen to use in breeding, Zabel said the study should not cause panic.
"It's a wait-and-see approach," he said. "We don't want people to worry about testing and throwing straws away."
Michael T. Osterholm, PhD, MPH, director of the University of Minnesota's Center for Infectious Disease Research and Policy, which publishes CIDRAP News, said the study should sound alarm bells for cervid farmers who have documented an introduction of CWD into their herds when it cannot be accounted for by animal movement.
"I have always been skeptical of cervid farmers who blame a positive CWD detection on contact with wild animals," said Osterholm. "Does transmission occur between animals on different farms that are shipping semen to closed farms having no other explanation as to how the deer get infected?"
Osterholm, who led the August [2019] launch of a CWD Resource Center at CIDRAP, said research should now take both an epidemiologic and laboratory approach to the problem of potential sexual transmission.
In related news, the Montana Fish, Wildlife and Parks agency announced yesterday [16 Jan 2020] that up to 13 percent of WTD in Libby, Montana could be infected with CWD. They said that's almost 3 times the agency's threshold for more aggressive management actions.
According to a story by Yellowstone Public Radio, the agency hopes to get permission from the state to sell an unlimited number of WTD tags, which would increase harvest activity outside of Libby.
[See also: 30 Dec 2019 PLoS One study
[Byline: Soucheray]
-- Communicated by: ProMED-mail from HealthMap Alerts
[In some ways, believing that CWD could be passed through semen makes some sense. After all, the prions have been found in the urine. We know urine has been a mechanism of transmission, which of course begs the question of why was urine allowed as bait or lure for so long (and perhaps still is in some states)? Therefore, urine and semen have some common tubes, most especially the urethra, to travel through. While this may sound like, and may be, a breakthrough in understanding, there remain questions. Was it in the testes before it was found in the urine? In other words, there is still much to understand, but perhaps this is another of the puzzle pieces for the CWD puzzle. - Mod.TG
The Michigan Department of Agriculture and Rural and Development (MDARD) has confirmed chronic wasting disease (CWD) in 3 white-tailed deer from a Newaygo County deer farm. All 3 deer were 4.5 years old. The samples were submitted for routine testing as part of the state's CWD surveillance program for farmed deer.
To date, CWD has not been detected in free-ranging deer in Newaygo County. As part of MDARD's disease response, an investigation will be conducted to rule out exposure of any other farmed deer.
"Chronic wasting disease is a serious disease affecting both farmed and free-ranging deer," said state veterinarian Nora Wineland, DVM. "MDARD and the Michigan Department of Natural Resources work together, in partnership with the state's deer farmers, to ensure the protection of all of Michigan's deer."
Since 2008, CWD has been detected in 4 additional privately owned cervid facilities from Kent, Mecosta, and Montcalm counties. The deer farm in Newaygo County is the 5th Michigan farm in which CWD has been detected.
Is it possible that ALL deer in a CWD area have CWD.... just not enough to be detected ?? Sorry in advance if that sounds like a stupid question.... Chris.
All positive results from the ELIZA test are sent to AMES lab for verification by the gold standard immuno staining of submitted tissue samples.
Analogy might be like water testing where the presence of nitrates (for example) are below detectable level and the water is safe to drink.
*The difference between immuno staining and ELIZA is that a screening assay allows for the testing of multiple samples in a timely manner. Immuno staining of tissue requires more "hands on" work by a lab tech and takes longer per sample. If the state did that, you would not get results back for months!
I've always been told that there is no stupid question.
I miss some things from MI, but am loving it here in WY. Have some great neighbors. I live in a town that is adjacent to the Bridger-Teton National Forest and have easy access. Looking forward to next fall.
We look and can walk to Cedar Creek Canyon trail. Two other access trails in our town.
The immunofluourescent test done for verification at the AMES lab is done on a single sample, so the amount of tech hands on per sample is much greater than the screening assay. Both of these tests require multiple manipulations (adding of reagents, wash steps, etc.).
My teleportation device is broken so I can't get to Kalamazoo this weekend for the Trad Expo. First time in years that I am missing it. ;o)
Chronic wasting disease (CWD) is difficult, if not impossible, to eliminate. The debilitating neurological disease that leads to death in deer and other cervid animals was found on a domestic deer farm in Avoca in the fall of 2018. The Quebec government recently reported that efforts to prevent the disease from spreading to the wild whitetail deer population have been successful. The measures taken by wildlife management authorities included the creation of an enhanced management area in the Laurentide and Outaouais regions where hunting regulations were relaxed in order to reduce the deer population.
However, it is impossible to completely remove CWD from the wild, if it is there.
The microscopic prions that contain [or cause] CWD can remain infectious for several years in the natural environment, according to the Quebec Ministere des Forets, de la Faune, et des Parcs (MFFP-Ministry of Forests, Wildlife, and Parks). A statement from press relations representative Catherine Ippersiel explained that the longevity of the CWD prion is unknown, but the prion for Scrapie, a similar disease that affects sheep, has been found to keep living for more than 16 years. Plants can absorb the CWD prion from soil contaminated from contact with infected deer or their feces, urine, or blood. The plants absorb the prion and can transfer the disease to other deer who eat the plants.
The MFFP does not consider any contamination of soil or plants in the natural environment outside the Avoca farm to be "significant." No positive samples from wild deer or other cervids in the region have been found, which in turn means that the possibility of the natural environment becoming present in the natural environment due to contact with wild deer is limited.
The incubation period for CWD is long. According to the MFFP, it usually takes 16-36 months [for] infected animals to show signs of having the disease, and testing has generally been ineffective at detecting CWD in animals infected for less than 12 months. In the region surrounding the Avoca farm, the MFFP will be continuing to maintain a low-density deer population, continuing enhanced surveillance to detect any emergence of CWD in the natural environment, and maintaining or improving measures to prevent new cases of the disease. For example, there are already regulations on moving or possessing certain parts of deer slaughtered near the affected farm.
Wildlife biologist Dr. Keith Munro confirmed assertions made by the MFFP and supported the measures it has taken. Munro works for the Ontario Federation of Anglers and Hunters (OFAH), which represents recreational hunters and fishers across the province.
"We don't actually know how long it lasts," Munro said in reference to the longevity of the CWD prions in the environment. There is no effective way of removing CWD from the wild landscape, he added.
Munro said the response by authorities in Quebec was important in order to prevent the cases of CWD in domestic deer from spreading to wild whitetail deer.
"If you have any cases, you have to respond really quickly," he said.
CWD was 1st detected in 1967, and there has never been a case in wild deer in Ontario. However, mule deer at the Metro Toronto Zoo died from an unspecified disease in the 1970s. Samples of tissue from those deer were re-tested many years later and found to be CWD.
Domestic deer farmers in Quebec are subject to all of the same animal welfare and accreditation regulations as other farmers are under provincial law. Municipalities can, however, regulate domestic deer farming using local zoning laws. In 2019, Grenville-Sur-La-Rouge effectively made deer farming impossible by limiting it to a very small portion of the municipality and requiring deer to be always inside a barn.
