FREQUENCY OF THE SCID GENE AMONG ARABIAN HORSES IN THE USA

Severe combined immunodeficiency disease (SCID) of horses is an autoso mal, recessive hereditary disease occurring among Arabian horses. The genetic defect responsible for this disease was recently identified as a 5-basepair deletion in the gene encoding DNA-protein kinase catalyt ic subunit (DNA-PKcs). Horses with one copy of the gene appear normal, while horses with two copies of the gene manifest the disease. The pr esent report describes a PCR-based test for detection of the gene defe ct and the results from testing 250 randomly selected Arabian horses. The frequency of SCID gene carriers was 8.4% (21/ 250). Based on the g ene frequency reported here, the authors would expect 0.18% (1 out of 567) of Arabian foals to be affected with SCID based on a random breed ing population.