I never heard of the bot cough, sorry..
The botfly lays eggs on the horse's legs, shoulder, mane, everywhere the horse can reach or another horse, when they groom each other. They itch, so the horse bites/licks at them. Saliva makes them hatch and they attach in the mucous membrane of the mouth. They stay there for about a week, then being swallowed and attach themselves on the stomach lining, where they stay and grow until spring, emerging with the poop, bury themselves in the ground and eventually become bot flies.
The mouth phase can make a sensitive horse go off feed for a day or two.
Best prevention is taking the eggs off daily with a bot knife or this grooming stone. Or wash them with warm water, they hatch outside the horse and can't do any damage.
Deworming after the first frost is recommended because the frost has hopefully killed the adult flies and you get the larvae in one time deworming with Ivermectine.
Last edited by deserthorsewoman; 09-18-2012 at 10:01 PM.