What are the common diseases and parasites in chickens?

Answer 1

Two common gastrointestinal diseases are endemic Newcastle's Disease and low-path avian influenza; both of these diseases circulate in the wild bird population, so any chickens exposed to wild birds are susceptible.

There are other diseases, but the frequency of them varies depending upon where you are located and how much exposure your chickens have to the outdoors.

Common parasites include mites, ticks and fleas; most chickens control these through dust baths and frequent grooming of their feathers, so unless it gets severe you don't need to worry about treating the chickens for these.