Chronic Wasting Disease, it is here and it seems to be growing in affected areas.
From the CDC to QDMA, there is talk about this disease that is sweeping the nation’s population of the mule deer, whitetail deer, elk, and moose.
There is a good amount of information regarding this neurological disease.
Let us go some of this information to get you caught up if you are not familiar with it:
What is Chronic Wasting Disease?
The website CWD-INFO.ORG defines it as…
a contagious neurological disease affecting deer, elk and moose. It causes a characteristic spongy degeneration of the brains of infected animals resulting in emaciation, abnormal behavior, loss of bodily functions and death.
CWD belongs to a group of diseases known as transmissible spongiform encephalopathies (TSEs). Within this family of diseases, there are several other variants that affect domestic animals: scrapie, which has been identified in domestic sheep and goats for more than 200 years, bovine spongiform encephalopathy (BSE) in cattle (also known as “mad cow disease”), and transmissible mink encephalopathy in farmed mink.
Several rare human diseases are also TSEs. Creutzfeldt-Jakob disease (CJD) occurs naturally in about one out of every one million people worldwide. Variant Creutzfeldt-Jakob disease (v-CJD) has been associated with the large-scale outbreak of BSE in cattle herds in Great Britain.
Even the CDC chimes in on the topic defining it as…
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.
As mentioned above there are no treatments or vaccines for this disease.
What does CWD do to the animals?
Again CWD-INFO.ORG lets us know that…
yearlings and even fawns can contract CWD (often getting the disease in utero from their mother), late-stage CWD symptoms are usually only visible in adult animals because of CWD’s long incubation period (usually around 18 months but may be as long as two years). In most cases, animals with CWD show no visible, outward symptoms of the disease for all but the last few months of the disease’s cycle. Thus, the majority of infected animals are virtually impossible to distinguish from healthy, non-infected animals. Because CWD affects the neurological system of an infected animal first, other causes of mortality (predators, vehicle collisions, other diseases) usually remove the animals from the population far before outward signs of the disease become apparent.
However, if an infected animal survives to the final stage of this always-fatal disease, the most obvious and consistent clinical sign is emaciation. CWD affected animals continue to eat but amounts of feed consumed are reduced, leading to gradual loss of body condition. Excessive drinking and urination are also common in the terminal stages.
Behavioral changes also occur in the majority of cases of late-stage CWD, including decreased interactions with other animals, listlessness, lowering of the head, blank facial expression and repetitive walking in set patterns. In elk, behavioral changes may also include hyper-excitability and nervousness. Excessive salivation, drooling and grinding of the teeth also are observed.
It is important to note that the above-mentioned clinical signs alone are not sufficient to definitively diagnose CWD. There are other maladies that have symptoms that mimic those of CWD such as brain abscesses, trauma-related injuries, or other diseases such as epizootic hemorrhagic disease. Currently, the only conclusive diagnosis for CWD involves an examination of the brain, tonsils or lymph nodes performed after death to detect the presence of CWD prions.
Where is this disease detected?
The QDMA site showcases a map that will show where there has been a confirmed diagnosis…
The one question we are asking is: Can we get CWD from our harvests?
The CDC has been researching this topic and has some information we can look at:
Scientists believe CWD proteins (prions) likely spread between animals through body fluids like feces, saliva, blood, or urine, either through direct contact or indirectly through environmental contamination of soil, food or water. Once introduced into an area or farm, the CWD protein is contagious within deer and elk populations and can spread quickly. Experts believe CWD prions can remain in the environment for a long time, so other animals can contract CWD from the environment even after an infected deer or elk has died.
The CWD prion has been shown to experimentally infect squirrel monkeys, and also laboratory mice that carry some human genes. An additional study begun in 2009 by Canadian and German scientists, which has not yet been published in the scientific literature, is evaluating whether CWD can be transmitted to macaques—a type of monkey that is genetically closer to people than any other animal that has been infected with CWD previously. On July 10, 2017, the scientists presented a summary of the study’s progress (access the recorded presentationExternalExternal and slides Cdc-pdf[PDF 3.88MB]External), in which they showed that CWD was transmitted to monkeys that were fed infected meat (muscle tissue) or brain tissue from CWD-infected deer and elk. Some of the meat came from asymptomatic deer that had CWD (i.e., deer that appeared healthy and had not begun to show signs of the illness yet). Meat from these asymptomatic deer was also able to infect the monkeys with CWD. CWD was also able to spread to macaques that had the infectious material placed directly into their brains.
This study showed different results than a previous study published in the Journal of VirologyExternal in 2018, which had not shown successful transmission of CWD to macaques. The reasons for the different experimental results are unknown. To date, there is no strong evidence for the occurrence of CWD in people, and it is not known if people can get infected with CWD prions. Nevertheless, these experimental studies raise the concern that CWD may pose a risk to people and suggest that it is important to prevent human exposures to CWD.
Additional studies are under way to identify if any prion diseases could be occurring at a higher rate in people who are at increased risk for contact with potentially CWD-infected deer or elk meat. Because of the long time it takes before any symptoms of disease appear, scientists expect the study to take many years before they will determine what the risk, if any, of CWD is to people.
This is from the American Society of Microbiology from the Journal of Virology:
Clinical observations of CWD-inoculated cynomolgus macaques.Clinical CWD in cervids presents primarily as a wasting syndrome, with other clinical signs including changes in behavior, polyuria/polydipsia, and excessive salivation (23). In SM, the main presenting sign of CWD was also weight loss, with other clinical signs such as weakness, inactivity, tremors, mild ataxia, and excess salivation, which varied between individuals (21). In our study, CWD-inoculated CM were monitored closely for signs of wasting, neurologic disease, and behavioral changes. Between 6.6 and 10.9 years after CWD inoculation, 5 monkeys developed weight loss; of these monkeys, 4 were confirmed to have diabetes, and 1 had no definitive diagnosis (Table 1). All the other CWD-inoculated monkeys were euthanized for a variety of medical conditions or neurologic signs or electively at the termination of the study at >13 years postinoculation (Table 1). Each euthanized CM was screened for prion disease by using prion disease-specific diagnostic assays, including the RT-QuIC assay for amyloid-seeding activity, examination of brains and spinal cords for neuropathology, and IHC and immunoblotting for the deposition of disease-associated prion protein (PrPSc).
And for the information for hunters who have harvested an animal that may have been infected, this question is answered on how we should proceed with our meat…
Hunters are recommended to not eat meat from animals known to be infected with CWD. Hunters in CWD areas are also advised to bone out their meat and to not consume those parts where prions likely accumulate.
In the absence of complete information on risk, and in light of similarities of animal and human TSEs, public health officials and wildlife management professionals recommend that hunters harvesting deer and elk in the endemic area, as well as meat processors and taxidermists handling cervid carcasses, should take some common sense measures to avoid exposure to the CWD agent and to other known zoonotic pathogens.
What are your thoughts about this disease affecting our enjoyment of the outdoors?