Dales Pony Society of America

Foal Immunodeficiency Syndrome (FIS)


Understanding Foal Immunodeficiency Syndrome

Foal Immunodeficiency Syndrome (FIS) was first identified in Fell Ponies and later in Dales. The syndrome is an inherited disease (it is not contagious, foals are born with it) resulting from a single recessive gene. “Carriers” are ponies that carry one copy of the faulty gene and one copy of the healthy gene. When two Carriers are bred together, there is a 1 in 4 (25%) chance that the foal will be syndrome foal. Syndrome foals will die within weeks of foaling.

Breeding a Carrier to an unaffected ("Clear") pony will give a 1 in 2 (50%) chance of the foal being a Carrier. Carrier foals do not have the disease but can pass on the gene to potential offspring.

Foals affected by the syndrome have a defective immune system and cannot resist disease properly – they die, usually within the first month or two of life, of problems including pneumonia, scouring, and anemia. To the best of our knowledge, the condition is invariably fatal.

All colts must be tested FIS Clear to be eligible for DPSA stallion licensing. Breeding mares, however, may be Carriers.

Currently, testing is only available in the United Kingdom. The current cost of a FIS test is £55. Visit the following Web site to learn more about testing your Dales for FIS: http://www.aht.org.uk/cms-display/genetics_fis.html . All stallions must be tested for FIS before a breeding license will be issued by the DPSA.


1. Does my pony have FIS?
If your pony is older than 3 months of age then NO, it will not develop FIS. However, it could be a Carrier and only testing will tell you for sure.

2. I want to buy a weanling, could it have the syndrome?
If it is old enough to be weaned, then NO, although again it could be a Carrier.

3. What is a Carrier?
A Carrier is a pony who is outwardly normal and healthy but whose DNA contains the gene for FIS. If a Carrier mare and a Carrier stallion are bred then there is a 1 in 4 (25%) chance of breeding an affected (syndrome) foal. If a Carrier is bred to an unaffected ("Clear") pony, there is a 1 in 2 (50%) chance that the resulting foal will be a Carrier.

4. How many ponies could be Carriers?
Unfortunately, we just don’t know. It has been suggested in Dales to be 12-15%, but this has not been proven.

5. I want to breed from my pony, could he/she be a Carrier?
Unfortunately, the only answer to this is: maybe. If the pony has previously produced a syndrome foal, then the pony IS a Carrier.

6. I want to breed from my mare, how can I tell if the stallion or my mare is a Carrier?
Ask the stallion owner to see a Certificate to see if he is FIS Clear. If the certificate can’t be produced, assume he is a Carrier and only use him on a Clear mare. You will have to test your mare to determine if she is Clear or a Carrier.

7. Should I avoid breeding from my Carrier mare?
No, but you must ensure that any stallion you use is Clear to avoid breeding a fatally affected foal. Breeding from a Carrier and a Clear pony will give you a 50% chance of breeding another Carrier and a 50% chance of breeding a Clear pony.