Friesian Horse Hydrocephalus

Quick Summary

Hydrocephalus is an inherited condition in Friesian and Friesian crosses characterized by excessive accumulation of fluid in the brain that results in severe cranial distension.

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Phenotype: Hydrocephalus is characterized by excessive accumulation of fluid in the brain that results in severe cranial distension. This condition often causes foals to be stillborn.

Mode of Inheritance: Autosomal recessive

Alleles: N = Normal/Unaffected, H = Hydrocephalus

Breeds appropriate for testing: Friesians, Friesian crosses

Explanation of Results:

  • Horses with N/N genotype will not have hydrocephalus and cannot transmit this hydrocephalus variant to their offspring.
  • Horses with H/N genotype will not exhibit the hydrocephalus phenotype, but are carriers. They may transmit this hydrocephalus variant to 50% of their offspring. Matings between two carriers result in a 25% chance of producing a hydrocephalus-affected foal.
  • Horses with H/H genotype will have hydrocephalus, foals are typically stillborn or euthanized at birth due to complications.

Turnaround Time
At least 15 business days; may be delayed beyond 15 business days if sample requires additional testing, or a new sample is requested.
Price

$45 one test per animal
$60 this test + one test from list below

$75 entire Friesian Health Panel (all 3 tests)

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.

Hairs with roots

7. Place the folded form containing the sample in a paper envelope and mail it to the laboratory.

 

Additional Details

Hydrocephalus is a condition characterized by excessive accumulation of fluid in the brain that results in severe cranial distension. It is thought to occur because of an abnormal narrowing of the jugular foramen (opening at the base of the skull) and can lead to dystocia in dams pregnant with affected foals. This condition often causes foals to be stillborn or to be euthanized at birth due to problems during parturition. A mutation (c.1423C>T) in exon 12 of the β-1,3-N-acetylgalactosaminyltransferase 2 (B3GALNT2) gene has been identified that is associated with this disorder. The mutation does not allow for the full-length protein to be produced, which compromises its normal function. Mutations in this gene also cause muscular dystrophy-dystroglycanopathy with brain abnormalities in humans.

Friesian hydrocephalus is inherited as an autosomal recessive trait. This means that affected foals have two copies of the defective gene and that the disorder occurs in males and females. It is estimated that about 17% of Friesian horses are carriers (N/H).

Testing for hydrocephalus is important to assist veterinarians in correct diagnosis and to assist owners in management and breeding decisions. Matings between two hydrocephalus carriers have a 25% chance of producing hydrocephalus-affected foals.