Ask veteran chicken keepers near you what they do. Where I live, it is hot and dry in summer and cold and dry in winter, the ground freezes, not sure how deep though. No one I've met (so far, we're kinda new here) worms their chickens. We haven't seen any evidence or signs of worm problems, so we don't worm our flock either. If you live in a hot, humid, moist climate, then worms are going to be more likely of a problem.
Some people worm never, some once a year, some quarterly or more. Depending on the medication used, you may have to toss eggs for 2-4 weeks, as the worm medicine can get passed on through the eggs.
There are no specific medicines for worming chickens. You have to use ones designed for goats or horses, at least that's how it is in the USA.
