Something’s not right in the woods, at least if you’re a white-tailed deer. In this episode, the guys dig into chronic wasting disease (CWD), a strange illness reshaping deer populations in many areas of the Lower 48 (and Scandinavia!). It’s not caused by a virus or a bacteria, but it is related to mad cow disease. They break down what it is, how it spreads, what’s happening inside infected animals, and why it’s so dang hard to contain. The deer are not alright… and there’s a reason.
This episode was recorded on April 23, 2026 at Walton Woods Park in Amherst, NY (a suburb of Buffalo).
Episode Notes and Links
Several questions came up during recording of the episode. Here’s what we found:
Are there different CWD strains in a single animal? Chronic wasting disease isn’t a single, uniform pathogen. It’s more like a shifting swarm. Infected deer can carry multiple prion “strains” at once, meaning different misfolded shapes of the same protein that behave in slightly different ways. They could spread through the body differently, build up in different tissues, and cause disease at different rates. Lab experiments show this most clearly: when CWD prions are passed through model systems, what looks like one strain can split into multiple distinct variants, or reveal that a mixed population was there all along (e.g., Angers et al. 2010 PNAS; Béringue et al. 2012 Journal of Virology; Li et al. 2010 Journal of Virology). In actual deer, the picture is harder to pin down, but studies comparing prions from different tissues and individuals show real strain diversity and suggest that more than one strain can exist within a single animal (e.g., Angers et al. 2009 Journal of Virology; Moore et al. 2016 Emerging Infectious Diseases). The takeaway is that CWD behaves less like a single disease agent and more like a moving target: a cloud of protein shapes, some dominant, some hidden in the background, that can shift over time, giving the disease more chances to adapt, persist, and potentially jump into new hosts.
Does repeated exposure to CWD reduce incubation time in deer? Repeated exposure to CWD prions does likely shortens incubation time, mainly because prion diseases are strongly dose-dependent. Higher cumulative exposure, whether from a single large dose or many smaller ones over time, can both increase the chance of infection and accelerate disease progression. Experimental studies in deer and elk show that animals exposed to higher or repeated doses tend to develop symptoms faster than those exposed once at low levels. In the wild, this likely plays out through repeated contact with contaminated environments like soil, plants, and carcass sites. That said, factors like genetics and prion strain can still influence how quickly the disease develops in any given animal.
Is CWD the only prion disease that affects wildlife? CWD is the only prion disease currently thriving as a self-sustaining epidemic in wild populations. The others mostly sit at the edges and are livestock diseases that occasionally spill into wildlife or appear in captive/wild interface cases. For example, scrapie occasionally “leaks” into the wild (it has been found in bighorn sheep), but it doesn’t take over. It flickers at the edges of livestock systems. Nothing like the landscape-level, self-sustaining spread we see with CWD. That’s what makes CWD so concerning: it’s not just present in wildlife, it seems to be built for it.
Steve talked about the possibility of vampire bats and wild hogs spreading CWD. What’s the story? There’s currently no evidence that vampire bats are spreading CWD, but the wild hog story has gotten more interesting recently. Blood-feeding bats like the Common Vampire Bat (Desmodus rotundus) are often mentioned because prions can occur in blood at low levels, but there are no peer-reviewed studies showing bat-mediated transmission, nor any field patterns linking bats to CWD spread. So the bat idea remains speculative. Wild hogs (Sus scrofa), on the other hand, have moved beyond pure theory. A recent peer-reviewed study (e.g., Soto et al. 2025 Emerging Infectious Diseases) detected low levels of CWD prion activity in free-ranging pigs in endemic areas, suggesting they can pick up and carry prions after scavenging infected carcasses. Combine this with earlier work showing prions can survive digestion and still remain infectious (e.g., Nichols et al. 2009 PLoS ONE), it all points to hogs as plausible mechanical vectors: in other words, organisms that can move infectious material without necessarily developing the disease themselves. The takeaway: vampire bats are still a biologically interesting but unsupported idea, while wild hogs are emerging as potential “messy middlemen,” capable of redistributing prions across the landscape, even if they’re not a primary engine of CWD transmission, which is still driven by deer-to-deer contact and long-lived environmental contamination.
Why doesn’t NYS do more free testing?
New York doesn’t offer broad, free testing for every deer. Not because it’s ignoring CWD, but because it uses a more targeted, strategic approach. There are a few key constraints on broad, free testing:
Cost & logistics: Each test isn’t just a swab. It involves lab processing (often PCR or amplification assays), trained staff, and sample handling. Scaling that to hundreds of thousands of deer is a major lift.
Low prevalence (right now): When disease prevalence is near zero, mass testing tends to return very few positives, so agencies prioritize early detection in hotspots instead.
Management strategy: Agencies often invest more in prevention (carcass transport rules, feeding bans, education) than broad surveillance.
Hunter participation: “Free for all” testing can overwhelm systems unless tightly managed, and many states have learned that targeted programs get better data per dollar.
So NYS is focusing its efforts on where they see it mattering most: high-risk areas, roadkills, sick/dead deer, and zones near known outbreaks—because testing every hunter-harvested deer statewide would be extremely expensive for relatively low yield in a state with no established CWD population.
More info on NY’s response, as well as what’s happening nationally:
The NYS Department of Environmental Conservation’s page on CWD (including information on how you can help, scroll down to “Members of the Public”)
CWD in Captive Deer: DEC’s Response in 2024
Chronic Wasting Disease Detection and Management: What Has Worked and What Has Not? A report by the CWD Alliance, a nonprofit organization focused on education, coordination, and outreach around chronic wasting disease. It was created to bring together a mix of stakeholders: state wildlife agencies, federal partners, scientists, and hunting/conservation groups to help share reliable information and improve how CWD is managed across North America.
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Works Cited
Bian, J., et al. (2022). Transmission of cervid prions to humanized mice demonstrates the zoonotic potential of chronic wasting disease. Acta Neuropathologica Communications, 10, 149.
Edmunds, D. R., Kauffman, M. J., Schumaker, B. A., Lindzey, F. G., Cook, W. E., Kreeger, T. J., Grogan, R. G., & Cornish, T. E. (2016). Chronic wasting disease drives population decline of white‑tailed deer. Ecology, 97(3), 620–632.
Henderson, D. M., Denkers, N. D., Hoover, C. E., Garbino, N., Mathiason, C. K., & Hoover, E. A. (2015). Longitudinal Detection of Prion Shedding in Saliva and Urine by Chronic Wasting Disease-Infected Deer by Real-Time Quaking-Induced Conversion. Journal of virology, 89(18), 9338–9347. https://doi.org/10.1128/JVI.01118-15
Küry, S., et al. (2023). The zoonotic potential of chronic wasting disease—A review. Pathogens, 12(3), 342.
Miller, M. W., et al. (2024). U.S. Geological Survey science strategy to address chronic wasting disease. U.S. Geological Survey Circular 1546.
Monello, R. J., Powers, J. G., Hobbs, N. T., Spraker, T. R., O’Rourke, K. I., & Wild, M. A. (2014). Endemic chronic wasting disease causes mule deer population decline in Colorado. PLOS ONE, 9(10), e110353.
Pirisinu, L., et al. (2024). Zoonotic potential of chronic wasting disease after adaptation in sheep. Emerging Infectious Diseases, 30(12).
Sandberg, M. K., et al. (2022). Humanized transgenic mice are resistant to chronic wasting disease prions from reindeer and moose. Journal of Infectious Diseases, 226(5), 933–942.
Saunders, S. E., Bartelt‑Hunt, S. L., & Bartz, J. C. (2012). Occurrence, transmission, and zoonotic potential of chronic wasting disease. Emerging Infectious Diseases, 18(3), 369–376.