Poison Prevention Horses investigate unknown things with their lips so all dangerous substances must be kept out of their reach. Use safe paint. Don't let horses get near junk or vehicles where they might ingest toxic paints, plastic, rubber, antifreeze, or battery fluid. Don't apply insecticides or herbicides near their feed or water areas and be aware of which way the wind is blowing when you are spraying. Read all labels very carefully or you might accidentally give your horse an overdose of an antibiotic, dewormer or nutritional supplement.
All horses have internal parasites.
The worm eggs in manure hatch into larvae that are eaten by the horse. Once inside the horse they subsist on the horse's blood while they mature, lay eggs and continue the cycle. Bots live inside the horse until the pupae drops to the ground with manure and hatches into a bot fly. Although bot flies look like bees, they don't sting but lay eggs on the horse's hair. Nose bots try to fly up the horse's nose, which causes most horses to strike viciously with their front legs and run frantically.