EVALUATION OF A TEST FOR IDENTIFICATION OF ARABIAN HORSES HETEROZYGOUS FOR THE SEVERE COMBINED IMMUNODEFICIENCY TRAIT

Objective-To determine whether a recently developed test would correct ly identify horses heterozygous for the severe combined immunodeficien cy (SCID) trait.Design-Case series. Animals-17 healthy Arabian horses that had previously produced foals with SCID, 1 healthy Arabian foal w hose dam and sire had produced foals with SCID, 4 foals with SCID, and 1 healthy non-Arabian foal. Procedure-DNA was extracted from leukocyt es or fibroblasts, amplified by means of polymerase chain reaction, an d hybridized with probes specific for the normal and mutant alleles of the catalytic subunit of DNA-dependent protein kinase, the factor who se absence is responsible for SCID in Arabian foals. Results-Amplified DNA from the healthy non-Arabian foal hybridized only to the probe sp ecific for the normal allele, whereas amplified DNA from the 4 foals w ith SCID hybridized only to the probe specific for the mutant allele. Amplified DNA from the 2 stallions and 15 mares hybridized with both p robes, as did amplified DNA from the healthy foal whose dam and sire h ad previously produced foals with SCID, indicating that these horses w ere all heterozygous for the SCID trait. Clinical implications-Results suggest that the genetic test will be useful in identifying Arabian h orses heterozygous for the SCID trait and foals with SCID, provided th at all Arabian horses with SCID have the same genetic mutation.