Extra stress makes a hoof more susceptible to this fungus.

Warco van de Halhoeve was diagnosed with white line disease two years ago, and the promising young show jumper spent most of a year recovering.
   
“In his first year at grand prix he has won two World Cup [qualifiers] and was second in another,” said his rider, Ali Nilforushan of San Diego, Calif. “He’s an amazing, great horse.”