Background: Warmblood fragile foal syndrome (WFFS) is a fatal, inherited connective tissue disorder in horses that shares similarities with
7 January, 2021
The research: An international team of scientists from Austria, Germany, Poland, and the United States, led by the UC Davis Veterinary Genetics Laboratory Director Dr. Rebecca Bellone, investigated the distribution of the WFFS allele across 38 different horse breeds in Europe and the USA, screening 4081 horses. They also probed the hypothesis that the WFFS allele originated in the Arabian breed. To assess the allele's prevalence in modern Arabians, they isolated DNA from 302 Arabians from diverse lines. To investigate whether the Arabian stallion Bairactar Or. Ar. (1813) was the founder of the allele, researchers isolated DNA from a museum specimen of his skeletal remains and analyzed it for the WFFS variant.
The results: 200 horses (4.9%) representing 21 breeds carried the WFFS allele. Most of these breeds were warmbloods; however, a few non-warmblood breeds also carried the allele. The non-warmblood exceptions include the Thoroughbred (carried by 17 out of 716 horses), the Knabstrupper (3/46), the Haflinger (2/48), and the American Sport Pony (1/12).
The WFFS allele was detected in 17 out of the 19 tested warmblood breeds, with the highest carrier frequency observed in Hanoverians and Danish Warmbloods (both approximately 17.3%). The allele was not detected in two warmblood breeds, the Swedish Warmblood and Zangersheide Warmblood, but sample sizes for both breeds in this study were small (n = 16 and n = 10, respectively). The average WFFS carrier frequency across all warmbloods tested was 11%.
The WFFS allele was not detected in any of the 302 Arabians tested, nor was it detected in the DNA sample isolated from the historical sire Bairactar Or. Ar., suggesting that an Arabian origin of the allele is unlikely. The origin of the WFFS allele remains unknown.
For more on this study see: Distribution of the Warmblood Fragile Foal Syndrome Type 1 Mutation (PLOD1 c.2032G>A) in Different Horse Breeds from Europe and the United States
