Typically deworming sheep is a "one time" treatment on an "as needed" basis, unless your vet gives directions otherwise. We deworm our sheep 2 to 3 times per year - sometimes more and sometimes less depending upon the weather and pasture conditions. Most producers would not recommend giving dewormers over an extended period of time as you could end up overdosing and injuring the animal, or continually underdosing and breeding drug resistant parasites. It would probably be a good idea to take some fecal samples in to your local livestock vet to be evaluated for other parasites as well. Nasal bots are gross and annoying, but they aren't nearly as dangerous to your sheep as some other parasites. Your vet can help you come up with a good deworming program to fit the needs of your flock.
