Do a worm count (incl fluke in that), then if your ground has not had goats/sheep on it in the last 12 to 18 months you should be fine if their worm count is low.
If you don't bring in new goats/sheep there is not much of a chance to get in worms I think. The do a worm count once a year. Hay doesn't bring in worms, only freshly cut grass would, silage should be ok too.