‘Zombie Deer Disease’ headlines sow confusion

Many out-of-state media outlets have taken to calling Chronic Wasting Disease (CWD) the “Zombie Deer Disease,” but that is not as far as the sensationalized headlines go. Recently, a headline appeared in Field & Stream and elsewhere touting a tale of two hunters who “died after eating CWD-positive deer meat.”

There are a few things we know about prion diseases such as CWD. One of them is that we do not have a vaccine or a cure for any human-contractable prion diseases. The other is that there is another prion disease called Creutzfeldt-Jakob Disease (CJD) that can, and has, affected humans.

Most hunters, and many others, have heard of CWD. It is an always-fatal neurological disease in cervids such as white-tailed deer and elk. It may take up to two years for clinical signs of the disease to show, but sick animals will exhibit behavior such as drooling, confusion, no fear of people and stumbling or lacking coordination. They can often be found near water as the disease causes an insatiable thirst.

Creutzfeldt-Jakob Disease (CJD)

CJD is a progressive central nervous system disorder caused by misfolded proteins. It is characterized by progressive deterioration of mental function. It leads to dementia, involuntary jerking of muscles and staggering. A variant of CJD has been linked to eating beef contaminated with a disease that has been called “Mad Cow Disease.” It can also be found in some people who inherit an abnormal gene. The disease progresses rapidly, with most people succumbing to it between four months and two years after they contract the disease. While there is no cure, there are some medications that may alleviate symptoms for a time.

CJD can come from three sources. It may occur spontaneously. It may occur in family genetics. It may be acquired, as in the case above, when eating contaminated meat.  Due to the third source of illness, the Centers for Disease Control have long warned against consuming meat from sick animals or from cervids, such as white-tailed deer, that have tested positive for CWD.

There has not been a recorded case of CWD being zoonotic, or “jumping” from cervids to humans. However, a recent study, the subject of the aforementioned sensationalized headlines, has come closer to showing a link could exist.

The study

The study was published by Neurology (neurology.org) on April 9, 2024. It was entitled: “Two Hunters from the Same Lodge Afflicted with Sporadic CJD: Is Chronic Wasting Disease to Blame?” It did not give a location of the two hunters, but said that one, a 72-year-old man, exhibited “rapid-onset confusion and aggression,” and that he had a history of consuming meat from a CWD-infected deer population. This man passed away in 2020. A friend of the man, who had also eaten meat from the same deer population, also “recently” died of CJD, although the timing of his death was not made clear. He passed away within a month of the initial presentation of his symptoms.

The abstract of the study stated that causation remained unproven. However, it was not possible to definitively rule out CWD in these two cases. This case did point to the need for more research of implications for public health. While clusters of sporadic CJD have the possibility to occur in regions with CWD-positive deer in their populations, this disease can occur elsewhere, meaning there is a possibility of the disease being zoonotic, but this is not conclusive evidence.

National Deer Association urges caution with study findings

Earlier this month, the National Deer Association released a lengthy statement regarding this study and the conclusions researchers made. It called for caution and accuracy in looking for any possible link from CWD to human health. The online report, the association said, served to cause a great deal of confusion. 

Evidence remains strong that CWD in cervids is not causing disease among hunters who consume infected meat. However, because the prion disease is still not fully understood, the best guidance is still to have all cervids tested for the disease and to not consume meat from a positive animal. 

“The brief report focuses on a 72-year-old man who died in 2022 of Creutzfeldt-Jakob Disease (CJD), a human disease that is similar to CWD in deer but never definitively connected through causation,” the National Deer Association report read, “We aren’t told where he lived. The man reportedly had a friend who also died ‘recently’ of CJD. We are given scant details about any of this, but according to the report, both men had ‘…a history of consuming meat from a CWD-infected deer population.’” 

The report goes on further to point out that the study did not make it clear whether the two men actually consumed meat from a deer that tested positive for the disease, only that deer in that population had tested positive. Because it is unknown even where in the country the hunters lived (although the study was done by researchers in Texas), even the prevalence of the disease in that population is not known. In many CWD-affected areas, prevalence is quite low, with a large majority of the population being healthy and free of disease. 

CJD is known to appear in localized clusters where it does appear, which would make this particular event not out of the ordinary for the disease. It affects approximately one in every 1 million people in the country annually, with most of those people being over 55 years of age.

Localized clusters of CJD have been researched in the past. None have been found to be linked to meat consumption from CWD-positive animals. 

Studies have been done in Colorado, Wyoming and here in Wisconsin with Dr. Joe Abrams of the Centers of Disease Control in Atlanta releasing preliminary data last summer regarding surveys of hunters in some of the oldest CWD outbreak areas. The study reviewed data from 2 million hunters going back 30 years. Hundreds of thousands of those hunters hunted in CWD-endemic areas. Abrams said there was no indication of those hunters dying at higher rates than the general population. The Wisconsin study identified almost 650 hunters who were known to have consumed meat from animals that tested positive for CWD and none of them had been diagnosed with a prion disease. However, it should be noted that finding one positive in 642 people would far surpass the average annual rate of one per million.

The National Deer Association statement reminds that there still, even with this study, has not been a proven case of CWD moving species or “jumping” to humans. They agreed that more research is needed, as the study authors suggested, and hoped the authors would provide more clarity and details from their study.

“Any assertion that CWD has spilled over into humans needs a full and comprehensive diagnostic investigation,” said Dr. Krysten Schuler, wildlife disease ecologist with the Cornell Wildlife Health Lab. “The implications of such a finding would have huge implications for wildlife and the hunting community.”

Beckie Gaskill may be reached via email at [email protected].