Equine Juvenile Spinocerebellar Ataxia (EJSCA)Quick Summary
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Phenotype: Affected foals develop ataxia, or incoordination, between 1 and 4 weeks of age. The disorder progresses within a few days until affected foals are unable to stand without assistance.
Mode of Inheritance: Autosomal recessive
Alleles: N = Normal/Unaffected, JSA = juvenile spinocerebellar ataxia
Breeds appropriate for testing: American Quarter Horse
Explanation of results:
• Horses with N/N genotype will not have equine juvenile spinocerebellar ataxia and will not transmit the JSA allele to their offspring.
• Horses with N/JSA genotype will not have equine juvenile spinocerebellar ataxia, but are carriers. They may transmit the JSA allele to 50% of their offspring. Breedings between two carriers result in a 25% chance of producing an EJSCA-affected foal.
• Horses with JSA/JSA genotype will have juvenile spinocerebellar ataxia.
Sample Collection
Horse DNA tests are carried out using cells from the roots of a hair sample (roughly 20-30 hairs).
1. Grab about 10 hairs at the base.
2. Wrap the hairs around your finger and give it a quick pull.
3. Check the ends to make sure the pulled hairs have roots.
4. Repeat the process until you have collected about 20-30 hairs with intact roots.
5. You can choose different places on the mane or tail. NOTE: For foals, we recommend pulling all hairs from the tail only.
6. Tape the hairs to the submission form and fold the form along the dotted line to protect the sample. Do not use ziploc bags as they can cause condensation that allows mold to grow on the hair.
7. Place the folded form containing the sample in a paper envelope and mail it to the laboratory.
A new neurologic disease of American Quarter Horse (QH) foals was identified in 2020. Affected foals developed ataxia, or incoordination, between 1 and 4 weeks of age. Glucose and gamma-glutamyl transferase (GGT) concentrations were commonly elevated in blood tests. Most foals exhibited severely affected hind limbs and less severely affected front limbs. As the disease progressed, these foals would turn the hind limbs to one side, with the front limbs planted on the ground, causing them to appear to walk sideways. Within a few days, the affected foals were unable to stand without assistance and had to be euthanized. Postmortem examinations revealed distinctive lesions in their spinal cords. This disease has been named Equine Juvenile Spinocerebellar Ataxia (EJSCA).
Whole genome sequencing was performed on a group of affected and unaffected related foals. Analysis of the results led to the identification of the genetic variant that causes EJSCA.
The disease is inherited as an autosomal recessive trait. A scientific paper describing this gene and the genetic mutation is currently in progress. This page will be updated when the publication becomes available.
Genetic testing can determine whether a horse is a carrier of the variant that causes EJSCA. Breeding of two carrier animals has a 25% chance of producing an affected foal.
