What Is Fell Pony Syndrome?

Fell Pony syndrome (FPS) is a fatal disorder of young foals of the Fell Pony breed.

FPS-affected foals are born healthy but rapidly fail to thrive and experience severe anemia and lymphopenia within several weeks of life.

Pedigree analysis of the breed suggests that FPS may have an autosomal recessive inheritance, and a recent genome-wide association study identified a mutation associated with the syndrome on chromosome ECA26 (22).

The mechanistic implications of this mutation have not been resolved. In the absence of effective therapies, careful breeding management is necessary to decrease FPS incidence.

This is of particular importance because the Fell Pony breed is already considered threatened due to the small population size globally (Rare Breeds Survival Trust).

In 2006, reports showed the first case of Fell Pony syndrome in the United States, along with others in the Czech Republic and the Netherlands (6, 23, 28). Most recently, a case of the same syndrome was reported in a Dales pony, a breed that also originated in England (21).

Fell Pony syndrome was initially described in the United Kingdom in 1998 (60). The fatal illness became clinically apparent in foals within 1 month, and death occurred generally by 3 months of life. Clinical and post-mortem examinations revealed a syndrome comprised of anemia, immunodeficiency, and peripheral ganglionopathy.