One Health Collaboration between UTMB and Texas Parks and Wildlife Department

By: Madeline Steck, MPH

Chronic Wasting Disease (CWD) is a prion disease that was first reported in the US (and globally) during the 1960’s and is known to affect many species of the cervid family including various species of deer, moose, and elk¹. Prion diseases are those associated with “misfolded” prion proteins that cause misfolding of other normal prion proteins naturally found in our brains. The characteristic symptom is neurodegeneration, which is ultimately fatal since there are no vaccines, cures or even approved treatments to prevent disease progression. Apart from CWD, other notable prion diseases of animals include Bovine Spongiform Encephalopathy in cows and Scrapie in sheep, as well as human prion diseases such as Creutzfeldt-Jakob Disease ².

Erin Lee (DVM, MS, DACLAM) and Douglas Brining (DVM, DACLAM) are two UTMB veterinarians leading a novel investigation into the transmission potential of CWD between two specific deer species present in Texas. Dr. Lee is a senior clinical veterinarian with the UTMB Animal Resources Center which oversees responsibility for all animal care on campus while Dr. Brining is both the attending veterinarian and program director. Their study team is primarily made up of veterinarians and wildlife biologists. No physicians are involved because human health is not being investigated in this project; however, the underlying concern for public health consequences of CWD on hunters and consumers of deer-meat is clear. Unlike Bovine Spongiform Encephalopathy (aka “Mad Cow Disease”) with its ability to infect humans, CWD is not yet known to infect humans. But as Lee explained, “It's an area of interest because humans like to eat deer and elk”. Prion diseases have long incubation periods between the time of infection and appearance of symptoms and CWD itself takes several years for infection to lead to death in cervids. Brining posed the question “Is it due to the slowness of when you might see clinical manifestations or are there manifestations that are just not recognized yet?”. The long-term implications of any unintended ingestion of CWD-infected tissues by humans are not known. For humans, the only scientific evidence is still inconclusive and based on a singular study surveilling a group of people that ate infected meat during a social event³.

CWD first appeared in Texas in 2012. With further discovery of the disease in both free-ranging and captive deer populations, the Texas Parks and Wildlife Department (TPWD) and Texas Animal Health Commission (TAHC) developed a cooperative management plan4. Many import research questions on CWD exist including whether CWD can be transmitted via environmental shedding of prions from the feces, urine, saliva, or blood of infected animals. The susceptibility status (ability to be infected) of many cervids is also unknown, especially for exotic species that are imported into Texas for the big game industry. It is now common for exotic deer to live alongside native species, including the white-tailed deer, that are CWD susceptible. Studying this intersection of animal health and predicted environmental transmission mechanisms is benefited by a One Health approach, especially with the additional concern of human health risks.

“The main driver for this study is to look at a different deer population, the axis deer (Axis axis), which are not regulated by the current CWD management plan. We want to determine if axis deer are susceptible to CWD transmission from white tailed deer (Odocoileus virginianus). And if so, does it progress into full blown CWD?”. For this study, TPWD will breed the deer and Lee and Brining’s team will conduct the CWD transmission experiments. The project aims to understand if axis deer will become infected and how environmental transmission may be involved. Another potential outcome is to see signs of illness; however, humane endpoints will be in place so that the deer will never have to endure severe illness.

References:

1. Centers of Disease Control and Prevention. “Chronic Wasting Disease (CWD)”. Reviewed 10 September 2021. Accessed 8 March 2023 from https://www.cdc.gov/prions/cwd/index.html
2. Centers of Disease Control and Prevention. “Prion Diseases”. Reviewed 17 November 2021. Accessed 8 March 2023 from https://www.cdc.gov/prions/index.html
3. Olszowy KM, Lavelle J, Rachfal K, Hempstead S, Drouin K, Darcy JM 2nd, Reiber C, Garruto RM. Six-year follow-up of a point-source exposure to CWD contaminated venison in an Upstate New York community: risk behaviours and health outcomes 2005-2011. Public Health. 2014 Sep;128(9):860-8. doi: 10.1016/j.puhe.2014.06.012. Epub 2014 Sep 13. PMID: 25225155.
4. Texas Parks and Wildlife, Texas Animal Health Commission. “CWD Management Plan in Texas”. August 2020. Accessed 10 March 2023 from https://tpwd.texas.gov/huntwild/wild/diseases/cwd/plan.phtml