You can rub the bot eggs off with a pumice stone if you are uncomfortable using a knife. Also, there is a product called "Ovitrol" spray that kills the eggs on contact so that they can never hatch. If you keep it applied during bot fly season, the eggs will die as soon as they land on the horse. (Also kills fleas, ticks, mosquitos, mites, etc.) Great stuff.
I saw on YouTube where bots had burrowed into a lady's chest and they had to dig out those maggots from the giant holes with tweezers. So yeah, I wouldn't go on YouTube to find bot fly info!! You'll be all kind of grossed out.
**I must not forget to thank the difficult horses, who made my life miserable, but who were better teachers than the well-behaved school horses who raised no problems.**