Breeds Affected: Arabian
Samples Accepted: Blood, Hair
Disease Information: Foals affected with SCID appear healthy at birth, but cannot develop a functional immune system. Affected foals normally die of infections by five months of age.
Inheritance Information: Animals which have two copies of this allele are affected with SCID, and animals with one copy are clinically-normal carriers.
The possible genotypes are:
N/N The horse is normal, and cannot produce SCID-affected offspring.
N/scid The horse is a carrier of SCID, and can pass the allele on to approximately 50% of any offspring. If bred to another N/scid carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.
scid/scid The horse is affected with SCID. This disease is fatal, and affected horses do not usually live long enough to reproduce.
– 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
Test Information: This mutation test identifies a 5 base deletion in the DNAPK gene.
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 the Online Mendelian Inheritance in Animals website.