Foal Immunodeficiency Syndrome (FIS)  is an autosomal recessive disorder, meaning the affected foal must receive a copy of the mutation from each parent. The mutation occurs in the SLC5A3 gene and results in a deficiency of B lymphocytes. Affected foals are unable to produce antibodies on their own and succumb to infection as the maternal antibodies supplied by the mare’s colostrums are lost at 3-6 weeks of age. Foals either die or fail to thrive to the point that they are humanely destroyed.

About 30% of Fell Ponies and 18% of Dales Ponies are carriers. The syndrome is also found in Gypsy horses, most likely due to crosses with Fell Ponies. Since carriers of the mutation show no outward signs, it is important to determine if a horse is a carrier for this mutation prior to breeding.

The cost is $45 for each test.