Wherever there is manure, there are parasite larvae. The life cycle of all horse parasites involves leaving the horse host via the manure and then reinfesting a new host. Parasite larvae can do great internal damage to a horse as they migrate through the tissues. When a horse eats from manure-contaminated ground, he ingests parasite eggs. Flies Stable flies breed in moist, decaying organic matter.
Manure is perfect breeding medium for flies.
The life cycle of stable flies is 21 to 25 days from egg to adult. A female often lays twenty batches of eggs during her thirty day life span. Each batch contains between 40-80 eggs. When the eggs hatch, the adult flies emerge ready to breed. The number of flies produced by one pair of adults and their offspring in thirty days is a staggering figure in the millions.