While no one is certain, experts think that another always-fatal prion disease—this one currently known to occur only in cervids such as deer, moose, and elk—may behave the same way if it should jump the species barrier and infect people.
Chronic wasting disease (CWD) has been decimating cervid populations throughout North America since it was first diagnosed in a captive Colorado mule deer in 1967. While mitigation measures such as hunting may help slow its spread, it can’t be stopped.
This is because cervids are ubiquitous and free ranging, the interval from infection to symptom onset can take years, and prions spread easily from animal to animal and through environmental contamination, which can persist for years.
Johnston’s daughter, Kristal Enter, 39, a fundraiser in Boston, is familiar with CWD and its potential implications for human health. “Seeing what my mom went through, I do not want anyone else to have to experience that, nor their family members,” she told CIDRAP News. “The more we’re on top of chronic wasting disease and thinking about it, the better.”
But the frightening thing is that, for well over a month during the recent US government shutdown, no one was watching the human disease landscape for CWD, a highly infectious disease with no treatment or cure.
If cases slip by, it will be too late
Nine days after the government shutdown began, all four staff members of the Centers for Disease Control and Prevention’s (CDC’s) National Center for Emerging and Zoonotic Infectious Diseases Prion and Public Health Office were sent home after receiving reduction-in-force (RIF) notices. While the end of the shutdown led all four to be reinstated through at least January, layoffs after that time are possible.
Within the past few months, two other researchers who had been part of the team also had to be let go after their fellowship contracts weren’t renewed, per the administration’s policy of blocking contract renewals.
The prion unit, which monitors the nation for human prion diseases, is part of the Division of High-Consequence Pathogens and Pathology. It launched in the mid-1990s in response to the outbreak of bovine spongiform encephalopathy (BSE, or “mad cow disease”) in UK cattle. BSE prions were inadvertently consumed by people who ate contaminated beef, causing the human form of BSE, variant CJD (vCJD). All infected people—more than 230—died.
The initial goal of the Prion and Public Health Office was to watch for any cases of vCJD in the US population. Since then, its focus has expanded to include advising hospitals on how to prevent and respond to prion contamination of instruments used in neurosurgery (prions are resistant to many usual sterilization methods), as well as working with state health departments on disease surveillance. Unit members also answer questions from the public.
Today, as CWD continues its inexorable march across the landscape, exposing more and more people, the prion unit’s priority is conducting surveillance for signs of a CWD species jump into high-risk people such as hunters. Without this expertise, no one will be able to evaluate whether a suspected case of CWD prion transmission to humans is likely from an animal.
The prion unit has launched several epidemiologic studies in collaboration with multiple states to look at whether more hunters are dying of prion diseases than would be expected.
As an example of the unit’s work, last spring, a cluster of CJD cases in Oregon was widely conjectured to be linked to CWD. Such cases require autopsy and an epidemiologic investigation to determine whether CWD was involved and, if so, what kind of public health measures are needed. The prion unit shared ideas and strategy with the Oregon state health department in this investigation, which, thankfully, found no link.
But experts say that without anyone looking for these deviations from normal—particularly given that signs of illness may take years to appear—cases could easily go unnoticed, and it will be too late to implement public health measures that could mitigate some of these consequences.
Lawrence Schonberger, MD, MPH, retired chief of the Prion and Public Health Office, said that, as was the situation with BSE, CWD containment efforts must continue. “Unlike with mad cow disease, however, these efforts to date have not been successful,” he said. Surveillance and research “should continue to help people recognize any emerging risk to humans from this agent now and in the future, when this agent’s pathogenicity [ability to cause disease] may change.”
‘Worst time to get rid of such a division’
Brian Appleby, MD, is director of the National Prion Disease Pathology Surveillance Center at Case Western University, which conducts diagnostic testing for human prion diseases and conducted Johnston’s autopsy. The CDC funds the center, which collaborates with the Prion and Public Health Office on public health efforts and research projects.
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