How Disease Influences Gene Variations in Rocky Mountain Elk

David Palenski
31st January, 2024

How Disease Influences Gene Variations in Rocky Mountain Elk

Rocky Mountain Elk

Photo adapted from: Quartl / CC BY SA (Source)
Chronic wasting disease (CWD) is a fatal prion disease affecting deer, elk, and moose in North America, with recent cases emerging in Europe[2]. Prions are misfolded proteins that cause progressive neurological damage. The disease’s spread poses a significant challenge for wildlife management, and understanding how animals respond to CWD is crucial. A recent study by researchers at the Wyoming Game and Fish Department[1] investigated the link between CWD prevalence and genetics in Rocky Mountain elk. The study focused on a specific gene, the prion protein gene, and a particular variation within it – an allele (version) at codon 132, where leucine (L) is present. Previous research had indicated that elk with one or two copies of this leucine allele (denoted 132L﹡) experienced a longer time before showing symptoms of CWD[3]. The Wyoming Game and Fish Department researchers aimed to determine if the presence of this protective allele was increasing in elk populations as CWD became more common. From 2011 to 2018, the team analyzed the genetic makeup of 997 elk from Wyoming. They used a technique called PCR (polymerase chain reaction) and Sanger sequencing to identify which version of the prion protein gene each elk possessed. Simultaneously, they examined CWD prevalence data collected through ongoing wildlife surveillance. The analysis revealed a clear correlation: for every 1% increase in CWD prevalence in a region, the likelihood of an elk having at least one copy of the 132L﹡ allele increased by 9.6%. This suggests that the protective allele is becoming more common in areas where CWD is widespread, indicating natural selection is occurring. However, the relationship wasn’t uniform across all areas. In some regions, the 132L﹡ allele was found even when CWD was absent, highlighting that local factors and variations in disease spread influence the evolutionary process. This finding underscores the complexity of CWD epidemiology and the importance of considering regional differences. Interestingly, the study also found that CWD infection isn’t rare in elk with the 132L﹡ allele. This challenges the idea that the allele completely protects elk and suggests that even these animals can become infected and contribute to disease transmission. This finding builds on earlier work that demonstrated prion shedding – the release of infectious prions into the environment – occurs even in early stages of the disease[3]. The Wyoming researchers suggest further investigation into how quickly elk with the 132L﹡ allele shed prions and whether the disease manifests differently in these animals is warranted. Understanding these factors is vital, as environmental contamination with prions is a major driver of CWD spread[4]. The implications for managing CWD are complex. While the increasing prevalence of the 132L﹡ allele might seem positive, the fact that these animals can still become infected and shed prions means the allele doesn’t offer a simple solution. The study emphasizes the need to consider how the spatial distribution of elk populations influences evolutionary outcomes and disease spread. This knowledge can help refine mitigation strategies, determining the appropriate scale and extent of actions needed to control CWD.

WildlifeGeneticsEcology

References

Main Study

1) Ecology and Chronic Wasting Disease Epidemiology Shape Prion Protein Gene Variation in Rocky Mountain Elk (Cervus elaphus nelsoni).

Published 30th January, 2024

https://doi.org/10.7589/JWD-D-23-00062

Related Studies

2) Evolution of Diagnostic Tests for Chronic Wasting Disease, a Naturally Occurring Prion Disease of Cervids.

https://doi.org/10.3390/pathogens6030035

3) Early and Non-Invasive Detection of Chronic Wasting Disease Prions in Elk Feces by Real-Time Quaking Induced Conversion.

https://doi.org/10.1371/journal.pone.0166187

4) Field validation and assessment of an enzyme-linked immunosorbent assay for detecting chronic wasting disease in mule deer (Odocoileus hemionus), white-tailed deer (Odocoileus virginianus), and Rocky Mountain elk (Cervus elaphus nelsoni).

Journal: Journal of veterinary diagnostic investigation : official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc, Issue: Vol 15, Issue 4, Jul 2003


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