Worms How to tell and what to do!

My first post! I saw a few of my chickens discharge a stool that was pure liquid so I did a little research and found that it could be a sign of worms. Is there anyway to be sure if your chickens have worms? Do you treat just the infected ones or the whole flock? Is there someway to treat them without having to destroy the eggs (medicine - wazine says not to use eggs during treatment)? Thanks in advance!