The FEI has already done the same to the showjumping horses that competed in Doha.

The dressage horses competed one week earlier than the showjumping. Since a showjumping horse tested positive, the FEI doesn't want to take any risks. 

Nineteen dressage horses and 17 para-dressage horses are now blocked in the FEI Database, which means they won't be able to compete at international shows for a while.