الفهرس 
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Abstract
The Arabian horse is commonly believed to be one of the oldest horse breeds and the only purebred in the equine world. It is the most valuable, expensive species of equine as it combines unique and different characteristics than other breeds and other species of animals, which qualify it to be the breed of choice for long distance trail competitions and international festivals, hence has a great role in the improvement of the country’s economy.
It is believed that 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 (DNA-PKcs). SCID 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 four to six months. The condition in the affected foals is lethal although some cases have been treated with bone marrow transplants, but it is of high cost and not effective in most cases. Although the carriers don’t affected with mutation, but detection of mutation will help to avoid of carrier-to-carrier mating and the birth of clinically affected foals
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. Live samples were chosen at random from the registered population as well as post-mortem samples from reported cases died at different ages in Arabians farms. No SCID cases were found among the examined groups.
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 to affected foal deaths, extended veterinary care and intensive but futile treatments. Application of the DNA test overall Egyptian population is recommended.