We had chickens long before we had peafowl. although still new to peafowl - our chicks (4-5 months old) are in the same coop as our chickens. they are separated by chicken wire for now, the chickens are free range and i just open the door in the morning. not ready to free range the peas yet. but when we're ready the wall will come down so they can go out too. but thats the only reason they're separated for now.
We take preventative measures, worming and antibiotics to both chickens and peafowl when they first arrived. and we've never had a problem. we did loose one peachick when we first got them, but they'd been inside and never seen the chickens so i don't think it had anything to do with them. we too will worm them 3-4 times a year. and when we worm them i also give them antibiotics (preventative dose). i'd brather prevent sickness than treat it. and i think if you take the precautions you'll have no problems.