Gene or Region: PLOD1
Reference Variant: C
Mutant Variant: T
Affected Breeds: Warmblood and Other Breeds
Research Confidence: High - Findings reproduced multiple studies
Explanation of Results: ffs/ffs = homozygous for Fragile Foal Syndrome, trait expressed ffs/N = heterozygous for Fragile Foal Syndrome, carrier N/N = no variant detected
General Description
Fragile Foal Syndrome is a connective tissue disorder resulting in joint laxity and extremely thin skin that is only loosely connected to the body. The skin is easily torn, resulting in lacerations, hematomas, and seromas across the foal. Affected foals are euthanized shortly after birth. As Fragile Foal Syndrome is a recessive disorder, horses must inherit two copies (ffs/ffs) to show the disease. Horses with only one allele (ffs/N) are known as carriers due to their ability to produce affected offspring.
Gene Information
PLOD1 is an enzyme involved in collagen synthesis. Mutations in mice and humans result in similar connective tissue disorders. The mutation observed in horses alters an amino acid, likely disrupting the function of the encoded protein.
References Monthoux C et al., “Skin malformations in a neonatal foal tested homozygous positive for Warmblood Fragile Foal Syndrome.” (2015) BMC Vet Res. 11: 12. PMID: 256373371.
West Nile Virus (WNV) is a mosquito-borne virus that can infect multiple types of mammals, including horses. Infection can lead to a series of severe symptoms, most commonly encephalitis – acute inflammation of the brain. Severe neurological symptoms develop in ~8% of exposed horses, and once symptoms manifest, the fatality rate ranges from 20-40% and is higher in older horses.