COLORADO SPRINGS. Colo. — Chronic wasting disease is a growing threat for deer, elk and moose in North America, infecting a larger portion of the populations each year.
The fatal disease attacks the neurological system and seems, at this point, impossible to cure. Adding another layer to this complicated issue is a recent discovery that might indicate that efforts to stop it have been misaligned, with silver-lined implications that could have dire consequences if not heeded.
"We've got to do something soon …why do the research if the problem disappears," said Dr. Frank O. Bastian, implying that if chronic wasting disease is not stopped, it could be detrimental to entire cervid species.
Chronic wasting disease (CWD) is considered a transmissible spongiform encephalopathy, or TSE, which puts it in the same class as mad cow disease. Traditionally, always fatal TSE brain diseases have been considered to be the result of a deformed protein called a prion and studied as such. But one group of scientists led by Dr. Frank O. Bastian believes this explanation might not be accurate for CWD or other TSEs.
In an article published in the American Association of Neuropathologists' Journal of Neurology and Experimental Neuropathology (November 2019), Dr. Frank O. Bastian, a neuropathologist currently with the University of New Orleans and formerly with the Louisiana State University Agricultural Center, and his team of researchers claim that CWD is caused by a spiroplasma bacterium. If that's the case, it could mean that decades spent looking for an answer in prions might be for naught.
Prion vs. Bacteria
In order to comprehend the potential impact of Bastian's claim, it's important to understand the difference between a bacterium and a prion.
One distinguishing factor is prions don't contain nucleic acid while bacteria do. This means attempts to destroy a disease-causing pathogen by breaking down the nucleic acid won't work on a prion.
Another crucial difference is that a prion is a deformation of a protein that already exists in the body, meaning the deformation of a native protein won't trigger an immune system response that bacterial microbes might. Keep in mind that vaccinations work because they intentionally trigger this immune response, thus training the body to recognize and fight certain pathogens.
While vaccines won't work on prion-caused conditions, they can work on a bacteria-caused disease, as is the case with typhoid. This could open the door for preventative vaccinations if CWD is bacteria-caused.
The claim that TSEs might be caused by a spiroplasma bacterium instead of a deformed prion allegedly came after Dr. Bastian was able to isolate a bacteria microbe from the tissues of TSE-infected animals, including deer with CWD. After the microbe was isolated in his laboratory setting, it was put back into healthy animals, which then developed spongiform encephalopathy. In other words, after this isolated bacterium was introduced to otherwise healthy animals, they developed symptoms characteristic of naturally occurring TSEs.
According to Bastian, this previously unidentified species of bacterium can be considered an extreme thermoacidophile that's very difficult to kill. Microorganisms found in acid mine drainages, deep sea vents and thermal hot springs often fall into this category. In order to determine this attribute, Bastian put the bacterium through several tests and it survived them all, including exposure to boiling, formaldehyde, gamma irradiation, and extreme acidity. This ability to test the unidentified bacterium due to the new ability to consistently grow the organism in a culture is something Bastian considers to be one of his greatest recent successes.
Bastian has been studying CWD for more than a decade. In 2007, he injected spiroplasma bacteria into laboratory animals, which reportedly led to the animals showing signs of CWD in less than two months. He believes that while prions might be deformed in CWD victims, these are merely a sign the disease is present, not the cause.
Despite Bastian's extensive research, his claim of CWD causation is not widely supported. According to John Eveland, project director of North American CWD Project, a large majority of scientists studying the subject hold to the belief that the disease is caused by a prion despite little progress in understanding CWD or preventing its spread over several decades of research. Eveland says that the funding for CWD research reflects this division, with virtually all funding devoted to prion research.
Implications for Humans
While there aren't official reports of CWD infection in humans, health organizations advise against eating infected meat and research is ongoing.
One study, started in 2009 by a group of Canadian and German scientists, is working to determine if CWD can be transmitted to macaques — a type of monkey that is genetically closer to humans than any other species that has contracted CWD. While the results have yet to be published in academic literature, the scientists have publicly presented their progress, which preliminarily showed that monkeys can be infected with CWD by eating the muscle or brain tissues of infected animals. At times, this transmission is said to have occurred prior to the infected animal showing symptoms. When Bastian was asked about this study, he wasn't willing to throw his support behind the data, acknowledging that it had yet to be published.
If transmission to humans is possible, it likely would put many at risk. One 2006-2007 estimate from the Center for Disease Control and Prevention indicated that more than two-thirds of Americans have eaten cervid meat. Keep in mind that TSEs tend to have a very long incubation period in humans, up to several decades, allowing the infection to go unnoticed for years.
While the verdict is out on whether or not humans are susceptible to CWD, other diseases in the TSE classification can be contracted by humans. One condition that is similar to CWD is Creutzfeldt-Jakob disease (CJD). Like CWD, CJD traditionally has been believed to be the result of a misfolded prion and is a fatal degenerative disorder that impacts the neurological system. Unlike CWD, which tends to have an incubation period of around 16 months in deer, CJD typically has an incubation period of decades in humans, with most people that show signs of the disease aged between 60 and 65. Some worry that if CWD is infecting humans, it might have a similarly long incubation period making the disease difficult to diagnose.
A Possible Solution
In the wake of Bastian's most recent research, North American CWD Project was formed to help advance his attempt to develop new diagnostic tests and vaccines related to CWD. Primary research for the project is now being conducted at the University of New Orleans' Advanced Materials Research Institute in the Bastian Laboratory for Neurological Disease Research. Field tests are expected to take place at a second research facility in Pennsylvania.
The group has targeted four areas it believes could help fight the spread of CWD. First, the group hopes to address a key problem with CWD — effectively determining which animals are infected. Currently, testing is a slow process that requires hunters to bring the carcass to a designated facility. North American CWD Project is pushing to develop a field diagnostic kit that will allow hunters to test the animal at the kill site. The next goal is to create a live-animal test. The group believes that better access to testing will prevent humans from ingesting potentially infected meat.
The group also aims to develop antibiotic vaccines that might prevent the spread of the disease — one that would be injectable for captive animals and another that would be oral for free-range animals. One major implication of CWD being caused by a bacterium and not a prion would be that vaccines could be an effective solution. The goal is to have the vaccines created within three years.
Finally, the group is trying to develop a cure for the human-infecting Creutzfeldt-Jakob Disease within 5-6 years, moving on to address additional neurological diseases such as Alzheimer's and Parkinson's within 6-10 years.
One roadblock to this plan of attack, according to project director John Eveland, is lack of funding considering that nearly all government and private money spent is spent on prion research.
The Debate Continues
Colorado Parks and Wildlife refutes the claim that CWD could be caused by a spiroplasma bacteria.
Support for their stance includes a 1982 study by Dr. Stanley Prusiner that demonstrated that the causative agent of another TSE disease was "most likely" protein based. This was concluded after a scrapie-infected brain remained infectious after bacteria destroying enzymes were introduced. When protein-neutralizing enzymes were introduced, the infectivity dropped.
In another 2006 study cited by Colorado Parks and Wildlife representatives (Irina Alexeeva, et al.), researchers found that no bacteria was consistently associated with scrapie, drawing the conclusion that the "agent responsible for TSE disease cannot be spiroplasma or any other eubacterial species."
One study conducted by Hilari Maree French (2011) had difficulty recreating research claims that supported the bacteria-causation of CWD. During this study, French found that three spiroplasma bacteria tested were each susceptible to common laboratory disinfectants. This same research introduced spiroplasma mirum to animals with no resulting infection. The species of bacteria that Bastian claims to have identified as the cause of CWD is not spiroplasma mirum.
The Association of Fish and Wildlife Agencies also disputes claims that CWD may be caused by something other than a prion. Their official statement is as follows: "We felt that until there was definitive proof otherwise, it was important that the Association go on the record as supporting the overwhelming scientific consensus that Chronic Wasting Disease is caused by mutated protein known as prions."
According to Eveland, claims that Dr. Bastian's research has not successfully been duplicated are false. According to Dr. Bastian, no one has adequately tried.
While Bastian's research has stoked the debate regarding what causes CWD, it seems as if official organizations are lagging when it comes to adopting findings from the study. Definitively determining the cause of CWD and garnering support from the larger scientific community will likely prove crucial in stopped the spread of this infection before it's too late.