Hydrocephalus in horses

Hydrocephalus is a life-threatening condition characterized by excessive accumulation of cerebrospinal fluid in or around the brain´s ventricles. This condition leads to a progressive skull enlargement, head deformities and increased intracranial pressure, which has a negative impact on brain function and is manifested by neurological disorders. Affected individuals may exhibit impaired coordination of movement, lethargy, difficulty suckling, seizures or behavioral disorders.

A genetically determined form of hydrocephalus has been confirmed mainly in Friesian horses, Belgian coldblood and warmblood breeds.

The disease is caused by a nonsense mutation c.1423C>T in the B3GALNT2 gene, which encodes an enzyme that is important for the proper function of cellular structures related to the development of nervous tissue.

The mutation is inherited in an autosomal recessive manner. This means that the disease develops only in individuals who inherit the mutated gene from both parents. Carriers of the mutated gene are clinically healthy, but they pass the mutation on to their offspring. In the case of mating two heterozygous individuals, theoretically 25% of the offspring will be completely healthy, 50% of the offspring will be carriers, and 25% of the offspring will inherit the mutated gene from both parents and will therefore be affected by this disease.

A genetic test can clearly reveal the genotype of the animal and is a suitable tool for breeders to prevent the unintentional breeding of affected foals.

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References:

Ducro, B.J., Schurink, A., Bastiaansen, J.W., Boegheim, I.J., van Steenbeek, F.G., Vos-Loohuis, M., Nijman, I.J., Monroe, G.R., Hellinga, I., Dibbits, B.W., Back, W., Leegwater, P.A. : A nonsense mutation in B3GALNT2 is concordant with hydrocephalus in Friesian horses. BMC Genomics 16:761, 2015. Pubmed reference: 26452345