Arabians, pure and part-bred
Friesians, pure and part-bred
Fell Ponies, Dale Ponies and Gypsy horses, pure and part-bred
Quarter horses and related breeds, pure and part-bred
Saddlebred and related breeds, pure and part-bred
Coat colour tests
Foal Immunodeficiency Syndrome (FIS) is a fatal inherited disorder that has been found in pure and part-bred Fell Ponies, Dale Ponies and Gypsy breeds. Foals with FIS are normal at birth, but within a few weeks develop severe anaemia and B-lymphopenia. If they are not euthenased they will die from the effects of opportunistic infections.
FIS is an autosomal recessive disorder. Autosomal disorders are equally likely to affect male or female horses, while "recessive" means that a horse needs to inherit the FIS mutation from both its sire and its dam to be affected. Horses that have inherited the FIS mutation from just one parent are called FIS carriers, and do not have physical signs of this disorder.
Our information and terminology is based on the sequences and content in Fox-Clipsham et al. (2011): doi:10.1371/journal.pgen.1002133
FIS has been found in pure and part-bred:
It may also occur in other breeds and crosses.