Frequency of the severe combined immunodeficiency disease gene among horses in Morocco.
Authors: Piro M, Benjouad A, Tligui N S, El Allali K, El Kohen M, Nabich A, Ouragh L
Journal: Equine veterinary journal
Summary
# Editorial Summary: SCID Gene Frequency in Moroccan Horse Populations Severe combined immunodeficiency (SCID) is a fatal autosoemic recessive condition affecting Arabian and Arabian-cross horses, caused by a specific 5-base pair deletion in the DNA-PKcs gene that renders affected foals unable to mount immune responses. Researchers tested 300 Arabian horses, 150 Arab-Barbs and 3 Anglo-Arabs in Morocco using DNA-based genotyping to establish carrier frequencies and trace the disease's introduction into the population. Twenty-one carriers were identified (7% of Arabians, 4% of Arab-Barbs and 33% of the Anglo-Arab sample), with pedigree analysis revealing that three imported stallions were responsible for introducing and disseminating the mutant allele throughout the Moroccan breeding population. For breeders, studmasters and veterinarians working with Arabian bloodlines—particularly those with Moroccan ancestry or international breeding connections—this finding underscores the critical importance of DNA testing before breeding decisions, as carrier-to-carrier matings will produce 25% affected foals that will require euthanasia. These results highlight how founder effects and international horse trade can rapidly establish deleterious recessive alleles in geographically discrete populations, making molecular screening an essential component of Arabian breeding programmes.
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Practical Takeaways
- •Breeders working with Arabian horses and Arabian crossbreds in Morocco should use DNA-based testing to identify carrier animals and prevent breeding of homozygous affected foals
- •Three specific imported stallions have been identified as carriers; their offspring should be systematically screened to prevent perpetuation of the SCID mutation
- •Genetic screening should be incorporated into breeding programs for Arabian and Arabian crossbred horses in Morocco to reduce the frequency of this lethal hereditary disease
Key Findings
- •21 horses were identified as SCID carriers in Morocco: 14 Arabian horses (7%), 6 Arab-Barbs (4%), and 1 Anglo-Arab (33%)
- •The genetic defect responsible for SCID is a 5-base pair deletion in the DNA-PKcs gene
- •Genealogical analysis identified 3 imported stallions as the source of the mutant DNA-PKcs gene dissemination in Morocco
- •SCID is an autosomal recessive hereditary disease primarily affecting Arabian and Arabian crossbred horses