UC Davis School of Veterinary Medicine Veterinary Genetics Laboratory

Hoof Wall Separation Syndrome in Connemara Ponies

Dr. Carrie Finno, Carly Stevens, and Dr. Danika Bannasch

Funding provided by the Morris Animal Foundation, UC Davis Center for Equine Health, and Merial

Hoof Wall Separation Syndrome (HWSS) is an inherited condition seen in Connemara ponies and typified by the dorsal hoof wall splitting away from underlying structures.  This hoof defect develops in young foals between one to six months of age. The condition results in afflicted ponies having to support weight on the sole of the hoof instead of the dorsal hoof wall.  Affected animals can become severely painful despite careful management; their quality of life can diminish and euthanasia may be necessary.  Even if the condition is initially controllable, ponies may still develop laminitis over time.

Description: Affected Hoof Square.tif Description: close-up cross section square 2.tif

Distal hoof wall lesions characteristic of HWWS

Affected hoof cross section, with arrow pointing to separation in the hoof wall

HWSS is particularly troubling for the Connemara community because the parents of affected ponies are themselves completely unaffected.  Although affected individuals do share common bloodlines, it is problematic to predict whether a particular breeding will produce a foal with unhealthy hooves.  Investigation into the underlying genetic cause of HWSS has the potential to inform these breeding decisions, and could also provide insight into the disease pathophysiology.

To investigate the underlying genetic cause of HWSS, a genome wide association study was performed and a strong association between disease status and polymorphisms in a two-megabase (Mb) region of the genome was observed.  Sequencing of candidate genes within this region is currently underway, and any functionally relevant genetic differences identified will be validated using a larger sample set.  Consequently, we are still collecting DNA samples from both affected and unaffected Connemara ponies.  If you are interested in submitting a sample, please contact Carly Stevens (cstevens@ucdavis.edu) or Miriam Aguilar (miraguilar@ucdavis.edu) for more information.

Veterinary Genetics Laboratory, Tel 530-752-2211, Email VGL