Frequency of the severe combined immunodeficiency disease gene among horses in Morocco.

The research paper is about a study conducted to determine the frequency of severe combined immunodeficiency disease (SCID) in Arabian and crossbreed Arabian horses in Morocco, using a DNA-based test.

Severe Combined Immunodeficiency Disease in Horses

• Severe Combined Immunodeficiency Disease (SCID) is a hereditary disease that primarily affects Arabian, or Arabian-crossbred horses. It is an autosomal, recessive disease implying that a horse needs to inherit the defective gene from both parents to develop the disease.
• The disease is caused by a mutation in the DNA-PKcs gene, a gene that encodes the catalytic subunit of DNA-dependent protein kinase. Specifically, the mutation responsible for SCID in horses is a 5-base pair deletion in the DNA-PKcs gene.
• SCID diagnosed horses have highly compromised immune systems, making them susceptible to various infections.

Objective and Methodology of the Study

• The primary objective of this study was to determine the incidence or frequency of the SCID gene in Arabian and Arabian crossbred stallions and mares in Morocco.
• The researchers utilised a DNA-based test to identify horses carrying the SCID gene.

Findings of the Study

• The results of the study reveal that out of a total number of horses tested, twenty-one were carriers of the SCID gene. The breakdown includes:
  1. 14 (7%) Arabian horses,
  2. 6 (4%) Arabian-Barb horses (a crossbred), and
  3. 1 (33%) Anglo-Arab horse (another crossbred).
• The researchers were also able to trace the spread of the SCID gene to three imported stallions. These stallions were identified as the original source of the mutants in the Moroccan horse population, having disseminated the mutated DNA-PKcs gene.

Significance of the Study

• This research provides valuable insights into the prevalence of SCID in the horse population in Morocco.
• By identifying the carriers of this gene, it could aid in preventing the spread of this disease by controlling the breeding of horses carrying the SCID gene.
• The identification of imported stallions as the source of the mutant gene also informs import control and breeding policies to prevent the spread of the disease.