Breeds Affected: Fell and Dales pony
Samples Accepted: Blood, Hair
Disease Information: Foals affected with FIS appear normal at birth, but as maternal antibiodies decrease, show symptoms of diarrhea and cough, followed by anemia and infections. Because they cannot develop a functional immune system, the disease is fatal. Affected foals are normally humanely euthanized between 4-12 weeks of Age.
Inheritance Information: Animals which have two copies of this allele are affected with FIS, and animals with one copy are clinically-normal carriers.
The possible genotypes are:
N/N The horse is normal, and cannot produce FIS-affected offspring.
N/fis The horse is a carrier of FIS, and can pass the allele on to approximately 50% of any offspring. If bred to another N/fis carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.
fis/fis The horse is affected with FIS. This disease is fatal, and affected horses do not usually live long enough to reproduce.
– Carriers may be bred to normal animals (N/fis x N/N) without any risk of producing affected offspring. The offspring should also be tested before breeding to determine if they are carriers or normal.
– Breeding two carriers (N/fis x N/fis) is not recommended due to the possibility of 25% of the offspring being affected.
Test Information: This mutation test identifies a single base change in exon 1 of the SLC5A3 gene.
Fox-Clipsham, LY., Carter, SD., Goodhead, I., Hall, N., Knottenbelt, DC., May, PD., Ollier, WE., Swinburne, JE.: Identification of a mutation associated with fatal foal immunodeficiency syndrome in the fell and dales pony. PLoS Genet 7:e1002133, 2011. Pubmed reference: 21750681. Doi: 10.1371/journal.pgen.1002133.
Further information is available at the Online Mendelian Inheritance in Animals website.