How Disease Influences Gene Variations in Rocky Mountain Elk

David Palenski
31st January, 2024

How Disease Influences Gene Variations in Rocky Mountain Elk

Image Source: Natural Science News, 2024

A silent and intriguing battle is being waged within the bodies of the Rocky Mountain elk in Wyoming, USA—one that centers around a mysterious disease and the genetic armor the animals may, or may not, possess. This disease, chronic wasting disease (CWD), is an insidious illness that slowly degrades the brains of deer, elk, and other cervids, leading to a heartbreaking decline marked by weight loss, erratic behavior, and eventual death. There's no cure, no vaccine, and the disease is spreading. Scientists are locked in a race to understand CWD, particularly how the elk's genes might play a role in resisting or succumbing to this fatal condition. At the heart of this struggle lies a tiny fragment of DNA within the prion protein gene at a specific location known as codon 132. The variation, or allele, of this gene that includes leucine (which is symbolized as 132L*), has been the focus of recent studies because it seems to be a factor in how long an elk can stave off the symptoms of CWD. In other words, elk with this genetic twist appear to have a longer grace period before the disease takes hold. Between 2011 and 2018, researchers embarked on a genetic exploration that spanned the Wyoming landscape, analyzing the genes of 997 elk. They were particularly interested in figuring out whether there was a connection between the presence of the 132L* allele and how widespread CWD was in the elk populations. By using PCR and Sanger sequencing, two techniques that allow for the reading of genetic information, the scientists painstakingly categorized the genetic profiles of these majestic creatures, searching for the existence of the valuable leucine allele. What they found was a pattern as intricate as the landscapes these elk call home. It turned out that for every 1% increase in the prevalence of CWD, the odds that an elk would have the protective leucine allele rose by 9.6%. This suggested that as CWD spreads, the pressure it exerts on the elk population could be selecting for individuals that carry this genetic variant. Yet, the story isn't so simple. Nature loves complexity, and the scientists noted that, in some areas, elk with the leucine allele were living in regions untouched by CWD. This indicates that the interplay between genetics and disease is not consistent across the board; the patterns differ from one region to another, influenced by a tapestry of ecological, geographical, and probably many unidentified factors. Furthermore, while the leucine variant at codon 132 does appear to lengthen the period before the onset of symptoms, it is by no means a shield against CWD. The researchers underscored that those elk carrying one or two copies of the 132L* allele were still vulnerable to contracting the disease, a fact that suggests there's more to the story. This understanding beckons further research, particularly in how these genetically different elk might shed the disease and affect strain diversity—concerns that hold significant implications for managing CWD in wild cervid populations. Deciphering these nuances could be key for wildlife managers in strategizing against CWD's spread, which could include herd culling, controlled burns, or altering landscapes to prevent disease transmission. Predicting how the dance between the elk's genetic defenses and the relentless advance of CWD will play out is fiendishly complex. Still, by piecing together the genetic puzzle and the impact of landscape on disease dynamics, we inch closer to understanding how these majestic animals might adapt over time to this deadly adversary. Pulling from these findings, conservation efforts may evolve to focus not only on the immediate fight against CWD but also on fostering genetic diversity within elk populations, which could, in turn, become a natural bulwark against the disease. Knowledge, as always, is power—and in this case, it could mean the difference between survival and extinction for an iconic species of the American West.



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

Journal: Journal of wildlife diseases

(DOI unavailable)

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