Fat Daddy X2. DE does not work internally to kill worms or eggs. It loses it's properties of being razor sharp when wet. It does work well on external mites and bugs when you use it on floors, nest boxes or even the birds themselves.
I would suggest a good chemical wormer to remove heavy infestations of worms. As Fat Daddy has suggested, Wazine is an excellent wormer to use.
2 Tablespoons per gallon of water for 24 hours. (it helps to remove their water an hour before roosting the night before so they are nice and thirsty the following morning. Repeat in 10 to 12 days to get any eggs that have hatched. Do not eat the meat, eggs or hatch any eggs for 14 days after the last dose.