HERDA Testing

Introduction * Article courtesy of Animal Genetics US

Hereditary Equine Regional Dermal Asthenia (HERDA) also known as Hyperelastosis Cutis (HC) is a genetic skin disease found in the American Quarter Horse.

Researchers at Mississippi State University and Cornell University believe that the origin of this genetic disorder may be the Poco Bueno's sire line. Symptoms of this disorder is a lack of adhesion within the layers of skin due to a genetic defect in the collagen that holds the skin in place. This defect causes the outer layer of skin to split or separate from the deeper layers sometimes tearing off completely. Areas under saddle seem to be most prone to these lesions often leaving permanent scares, preventing the horse from being ridden.

The disorder is recessive, which means that a horse must be homozygous positive or have two copies of the defective gene to suffer from the disease. Consequently both the sire and the dam must possess at least one copy of the mutated gene in order for the offspring to be afflicted. Offspring born with one copy of the defective gene and one non-defective copy are considered a carrier and have a 50% chance of passing the defective gene on.

Although there is no cure for the disorder, Animal Genetics has developed a simple DNA test to detect a single nucleotide polymorphism (SNP) mutation with a high degree of association to this disorder. Animal Genetics offers DNA testing and detection of the gene mutation responsible for Hereditary Equine Regional Dermal Asthenia (HERDA) also known as hyperelastosis cutis (HC).

Herda Results Designation:

nn: - Non-Herda. Negative for associated HERDA gene mutation.

nHrd: - Heterozygous. Positive for recessive HERDA gene mutation, carrying one inherited copy. Skin disease will not take effect in Heterozygous horses. Will pass the HERDA gene to 50% of foals, and if bred to another HERDA carrier may produce HERDA offspring with associated skin condition.

HrdHrd: - Homozygous. Positive for recessive HERDA gene mutation, carrying two inherited copies. Skin disease will take effect to some degree, Homozygous horses will pass the HERDA gene to 100% of foals regardless of mate - however will only produce foals with Skin condition if bred to another carrier.