New research has identified specific genetic markers linked to Recurrent Laryngeal Neuropathy (RLN), a disease that significantly impacts the performance of Thoroughbred racehorses. This discovery, hailed as a major step forward in combating this debilitating condition, paves the way for the development of a genetic test to identify horses with a threefold increased risk of developing RLN. 
(c) Miltudog Dreamstime.com
Often referred to as laryngeal hemiplegia or "roaring," RLN is an upper respiratory tract (URT) disorder that affects up to 18% of Thoroughbred horses. The condition is characterised by the progressive degeneration of the recurrent laryngeal nerve, which controls the muscles that open the horse’s airway. As the disease progresses, airflow during exercise becomes restricted, leading to laboured breathing, reduced oxygen intake, and impaired athletic performance.
RLN represents a significant challenge for the Thoroughbred racing industry due to its economic and competitive implications. While pre-purchase examinations, including upper respiratory endoscopy ("scoping"), can detect RLN, resting evaluations in young horses often fail to identify the disease or predict its future onset.
To tackle these challenges, researchers at University College Dublin, in collaboration with Equinome and a world-class Thoroughbred training facility, conducted an extensive study funded by Research Ireland. The research team employed state-of-the-art diagnostic methods, including resting and overground exercising endoscopy of the upper airway, as well as laryngeal ultrasonography. This rigorous approach ensured accurate phenotyping of horses as either RLN cases or controls.
The study analysed over 200 Thoroughbred horses in training, utilizing both clinical evaluations and genetic testing. The case-cohort group was supplemented with detailed questionnaires to capture additional phenotypic data. A full report of the research is published in the Equine Veterinary Journal.
Using advanced DNA technologies, researchers conducted a genome-wide association study (GWAS) to identify genetic variants associated with RLN. They genotyped 43,831 single-nucleotide polymorphisms (SNPs) from 235 horses (110 RLN cases and 125 controls) and estimated the heritability of the trait. The findings revealed a set of genetic markers that significantly contribute to RLN risk, independent of other factors such as height.
This discovery is particularly important because it confirms a genetic predisposition to RLN and identifies specific markers that could be used to predict the disease in Thoroughbreds.
This research marks a significant advance in equine genetics and respiratory health, offering new hope for addressing RLN, a disease that has long plagued the Thoroughbred racing industry. The ability to identify horses with a higher genetic risk for RLN has far-reaching implications for the Thoroughbred racing industry.
The next step will involve translating these findings into a practical genetic test that can be readily adopted by breeders, trainers, and veterinarians.
UCD Professor in Equine Genomics and Chief Science Officer at Equinome, Emmeline Hill said the new findings would “lay the groundwork for the development of a genetic test to improve the welfare of horses that have a genetic predisposition to the disease.
“As well as identifying horses with an increased risk of disease, this new information could also inform breeding guidance to reduce the incidence of the disease and provide targets for new therapies.”
Project lead Lisa Katz, UCD Professor in Equine Internal Medicine, added: “Understanding the genetic risk of your horse for roaring can help with early intervention and management. This might include monitoring highly predisposed horses more closely and considering surgical interventions at an earlier stage to improve treatment success.”
For more details, see:
A genome-wide association study for recurrent laryngeal neuropathy in the Thoroughbred horse identifies a candidate gene that regulates myelin structure
Charlotte L. McGivney, Beatrice A. McGivney, Gabriella Farries, Katie F. Gough, Haige Han, Amy R. Holtby, David E. MacHugh, Lisa Michelle Katz, Emmeline W. Hill
Equine Vet J (2025)
No comments:
Post a Comment