Severe combined immune deficiency (SCID)
Severe combined immune deficiency (SCID) can appear in pure- and part-bred Arabians. Horses affected by SCID lack a functional immune system and are unable to fight infections. In their first few months foals are protected by antibodies in the mare's colostrum but as this protection declines their lack of immune system becomes apparent. The most common signs are respiratory illness, intermittent fever and/or diarrhoea. There is currently no effective treatment for SCID.
SCID is an autosomal recessive disorder. Autosomal disorders are equally likely to affect male or female horses, while "recessive" means that a horse needs to inherit the SCID mutation from both its sire and its dam to be affected.
Gene or region and technical reference
Gene: DNA-PKcs (causative). Reference: Patent (ceased)
n. Test developed using animal controls.
SCID. Test developed using animal cases.