Hydrocephalus (HCP)


Turnaround: 3-5 days

US: $45.00 | UK: £35.00

Breeds: Appaloosa/Friesian, Arabian/Friesian Cross, Baroque Pinto, Belgian Draft Horse, Friesian, Friesian Cross, Mixed Breed, Moriesian, Stonewall Sporthorse, Unspecified, Warlander


Hydrocephalus is a developmental disorder involving an accumulation of cerebrospinal fluid within the skull. This disorder typically causes a large abscess on the head. This often results in foals born prematurely, stillbirth of affected foals, and dystocia in dams during the birthing process. In Friesian and other horse breeds, hydrocephalus is inherited as an autosomal recessive disorder. This means that two copies from either parent are needed in order for the horse to display symptoms.

A nonsense mutation (a type of mutation that codes for a premature stop in DNA code) was found to be associated with hydrocephalus in a number of horse breeds. Hydrocephalus is primarily a result of years of inbreeding in the horse population and the widespread use of only a few influential ancestors.

Foals can only be affected by hydrocephalus if the foal inherits the disease from both parents. Parents that are carriers do not have any symptoms associated with the disorder. If breeding two carriers together, there is a 25% chance per foal born of developing symptoms of hydrocephalus. There is a 50% chance per foal born that they will inherit a copy of the mutated gene and become a carrier of hydrocephalus. This makes genetic testing an important tool while breeding.

Possible Results

Genotype Description
HCP/HCP Affected: Horse has two copies of the mutation causing Equine Hydrocephalus and will exhibit signs of the disorder.
N/HCP Carrier: Horse has one copy of the mutation causing Equine Hydrocephalus. Horse has a chance of passing this gene on to any offspring.
N/N Clear: Horse is negative for the mutation causing Equine Hydrocephalus and will never produce and affected foal.