Turnaround: 3-5 business daysTurnaround: 7-10 business days
Price: $40.00Price: £30.00
Breeds: Appaloosa/Quarter Horse, Arabian/Quarter Horse, Quarter Cross, Quarter Horse, Quarter Pony, Quarter/Paint Horse, Quarter/Stock Horse, Quarter/Thoroughbred
Description
Equine Juvenile Spinocerebellar Ataxia (EJSCA) is a fatal autosomal recessive neurological disorder first identified in American Quarter Horse foals in 2020. Affected foals are born normal but rapidly develop severe pelvic limb ataxia, asymmetric gait deficits such as “sideways walking,” and limb weakness between 1 and 5 weeks of age, usually alongside elevated blood glucose and GGT levels.
The condition is caused by an intronic variant in the ferredoxin reductase gene, FDXR-203 c.177+1778G>C, which creates a cryptic exon and disrupts mRNA splicing. This reduces FDXR transcript and protein levels and leads to severe axonal and myelin degeneration along the spinal cord’s dorsal spinocerebellar tract. It is the first non-coding neurological variant identified in horses and the first known genetic cause of a degenerative axonopathy in the species.
The disorder progresses swiftly to complete recumbency and there is no effective treatment, so humane euthanasia is necessary. Because affected foals do not survive and carriers show no signs, every affected foal comes from a carrier-to-carrier mating. DNA screening of breeding stock is the only way to identify carriers and avoid pairings (N/JSA x N/JSA) that carry a 25% risk of producing an affected foal.
Possible results
| Genotype | Description |
|---|---|
| JSA/JSA | Affected: Horse has two copies of the JSA variant and is expected to develop signs of the disorder. |
| N/JSA | Carrier: Horse has one copy of the JSA variant and is not expected to show signs of the disorder. Each offspring has a 50% chance of inheriting the variant. |
| N/N | Clear: Horse does not carry the JSA variant and cannot pass it on to offspring. |
Breeds Affected
Appaloosa/Quarter Horse, Arabian/Quarter Horse, Quarter Cross, Quarter Horse, Quarter Pony, Quarter/Paint Horse, Quarter/Stock Horse, Quarter/Thoroughbred
Reference
[PMID: 42160398]