Good pasture maintenance is the most important step in reducing parasites in horses. Parasite eggs, having been dropped in the horse's manure, are then eaten along with the grass. Keep your pastures clear of old manure. Allow pastures to rest if possible. Keep stalls clean and dry.
Fly sprays may help repel bot flies and many people pull the small yellow eggs off of their horse's hair coat so the horse does not ingest them.
It is also important to deworm any new horse that comes on the property before you turn it out on pasture.

