Severe Combined Immunodeficiency Disease (SCID Horse)

• Recurring severe infections
• Severe course of infections

• Severe Combined Immunodeficiency Disease (SCID) causes improper development of cells of the immune system (T- and B cells) resulting in severe, non-specific infections → usually lethal.
• Foals appear healthy at birth, but usually die of infection within the first 6 months.

This test detects the deletion of 5 basepairs (c.9478_9482del) in the DNAPK gene.

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Inheritance: autosomal recessive

→ Only horses with two copies of the variant (scid/scid) are affected. Horses with only one copy of the variant (N/scid) are clinically healthy carriers.

Genotypes:

N/N = normal

The horse has no copies of the genetic variant causative for SCID and therefore cannot pass it on to its offspring.

N/scid = a carrier

The horse is clinically healthy. The genetic variant will be passed on to the offspring with a probability of 50%.

scid/scid = affected

If the horse lives long enough to reproduce, the variant will be passed on to all offspring. All offspring will be carriers (N/scid).

• Carriers may be bred to normal animals (N/scid x N/N) without any risk of producing affected offspring. The offspring should also be tested before breeding to determine if they are carriers or normal.
• Breeding two carriers (N/scid x N/scid) is not recommended due to the possibility of 25% of the offspring being affected.
• Affected animals (scid/scid) should not be used for breeding.

Shin, E.K., Perryman, L.E., Meek, K.: A kinase-negative mutation of DNA-PK(CS) in equine SCID results in defective coding and signal joint formation. J Immunol 158:3565-9, 1997. Pubmed reference: 9103416.

Further information is available at Online Mendelian Inheritance in Animals.