Coryzoa is to be treated with either Tylan or a tsp of Galliymicin powder & 1 tablespoon of Sulmet/ Aureomycin powder to a gallon of water for 7 days. After 7 days take out the Sulmet/ Aur and up the Galliymician to 2 tsp for another 7 days. Then vaccinate all birds 3 months or older with Coryzoa vaccine. repeat in 4 weeks. Any bird showing symptoms after 2-3 weeks are carriers and should be culled. Vaccinate birds yearly and any new birds.
