<P> Foal immunodeficiency syndrome (FIS), originally known as Fell pony syndrome, mainly affects two breeds of ponies: the Fell and Dales . FIS is a recessive genetic disease . Affected foals appear normal at birth, but become weak, and either die or are euthanized by three months of age due to persistent infections caused by immunodeficiency . </P> <P> Affected foals are healthy when born . By one month of age, foals become depressed, lose weight, and have diarrhea, and a cough with nasal discharge . The diarrhea and cough initially improve in response to treatment, but then worsen as treatment becomes ineffective . The foal's coat becomes dry and staring and the foal weakens further by two months of age as the foal fails to suckle, and by the age of 3 months, the foal dies (or is euthanized), giving this disease a 100% mortality rate . </P>

Foal immunodeficiency syndrome in the fell and dales pony