How often you worm your birds depends on your environment. Warm moist or wet soil will require frequent wormings. Cold or mountainous or hot desertlike soil requires less frequent wormings.
One female large roundworm lays over 100,000 eggs a day contaminating your soil which will be picked up by other chickens and consumed starting the worms lifecycle all over again.
Worms suck the life out of chickens, starving them, multiplying. They weaken the chickens immune system opening the door for all kinds of diseases which eventually spread through a flock. The root cause being worms.
By the time you see worms in feces, internal damage has occurred. There are only two reasons why you would see worms in feces: A worm died of old age and was excreted, or the there wasnt no more room in the guts and they were excreted.
Why would a parasite leave its host?
It's important to worm birds, as well as keeping everything as dry as possible and rotating areas where birds forage. Sand in the pens helps keep everything dry.
I use sand in the coops and some of the nest boxes as well.
