Geography and weather affect deworming schedules. Hot, dry climates are the least hospitable environment for parasites transmission; moist, warm environments are the most hospitable. Some parasite eggs are killed by dry, hot temperatures above 85°F at ground level; others can stay viable for long periods even in hot or freezing conditions. Fortunately, transmission during those times are low. A special note for summer – when flying insects emerge, summer sores and other parasite related conditions can develop, and bot eggs may be visible on horse’s legs and elsewhere. The age of your horse, where they are housed and grazed, how much they travel, and other conditions also affect deworming schedules. Young horses are prone to infestation with roundworms (ascarids) and typically need the most frequent deworming schedule. Some older horses develop abilities to cope naturally with parasites, while others may experience more parasite issues. Grazing horses and horses that travel come in contact with a greater variety and quantity of parasites that may cause damage and decrease performance.