Well....worming chickens definitely has 2 camps - some people worm their chickens regularly, others don't. I fall into the latter category - I have found no evidence of worms in my flock until very recently. Then I wormed with herbal remedies.
So to answer your question - chickens will start to be lethargic, laying goes down, combs can become anemic. If you are concerned take a fecal specimen to the local vet. S/he may not be a bird specialist but they should be able to find worms. If found, you have a couple of choices. First is to treat with regular worming medicine, all of which I believe, require an egg withdrawal period - I may be wrong on this. Your second choice is to treat herbally. Many people swear by herbal tinctures etc. This is what I used recently on my flock and the hen in question seems to be better now.
hope this helps,
