| Contents |
|---|
| Foal Immunodeficiency Syndrome (FIS) |
| Summary |
| Understanding the Results |
| Disease Name and Genes |
| Inheritance |
Foal Immunodeficiency Syndrome (FIS)
Summary
Foal Immunodeficiency Syndrome (FIS) is an inherited disorder of the immune system that manifests as B-lymphocyte immunodeficiency and progressive anemia. Affected foals appear to be normal at birth, but develop infections within a few weeks. The infections are resistant to treatment, and foals die or are euthanized by three months of age.
The condition is found in two rare related British pony breeds, the Fell and the Dales. A significant percentage (10%) of the Fell ponies born each year die from FIS.
Date of Last Update: 08/02/2016
Results
Understanding the Results
Results of the genetic test for FIS are presented as shown below.
| Foal Immunodeficiency Syndrome (FIS) | ||
|---|---|---|
| N/N | Clear | This horse tested negative for FIS. |
| N/FIS | Carrier | Both the normal and mutant alleles are present. This horse is positive for the FIS mutation but will not develop symptoms. |
| FIS/FIS | Affected | This horse carries two copies of the FIS mutation and will die of the disease. |
Disease Name and Genes
Foal Immunodeficiency Syndrome (FIS) is associated with a Proline (P) to Leucine (L) substitution at amino acid position 446 of the sodium/myo-inositol cotransporter gene (SLC5A3-P446L).
Inheritance
Foal Immunodeficiency Syndrome (FIS) is caused by a recessive variant of the SLC5A3 gene (SLC5A3-P446L). The recessive allele is commonly abbreviated as FIS, with the dominant wild-type allele abbreviated as N.
Carriers of the recessive allele (N/FIS) have no symptoms of the disease. If two carriers are bred, each foal has a 25% chance of having two copies of the normal allele (N/N), a 50% chance of being a carrier (N/FIS), and a 25% chance of being affected (FIS/FIS).
If a carrier of the recessive allele (N/FIS) is bred to a normal horse (N/N), each foal has a 50% chance of having two copies of the normal allele (N/N) and a 50% chance of being a carrier (N/FIS).
