Molecular Detection of Severe Combined Immunodeficiency Disorder in Arabian Horses in Egypt

Severe combined immunodeficiency (SCID) is a fatal genetic disorder and one of the common genetic diseases of the Arabian horse. The genetic mutation responsible for this disease is a five base pair deletion (TCTCA) in the DNA-protein kinase catalytic subunit gene. Severe combined immunodeficiency is a recessive autosomal genetic disorder with 25% chance inheritance of the disease among the progeny of carrier parents. It causes complete absence of certain immune cells, like B and T lymphocytes, leaving foals with immunodeficiency and exposing them to early death within 4 to 6 months. This study aimed to establish a reliable DNA test for detection of asymptomatic SCID carriers in the Egyptian Arabian horse population and to re-examine cases of unexplained foal death to exclude presence of SCID disease. Samples collected from live horses were chosen at random from the registered population, as well as postmortem samples from reported cases died at different ages in Arabian farms. Among these samples, we did not identify SCID carriers. Improved SCID diagnostic assays will help in selection within breeding programs to avoid carrier-to-carrier mating and the birth of clinically affected foals. This will have a positive effect on the financial value of Arabian horse production by decreasing economic losses due to affected foal deaths, extended veterinary care, and intensive but futile treatments. Application of the DNA test overall Egyptian population is recommended.