Coccidiosis is host-specific, meaning the coccidia that affect chickens do not affect turkeys or other chickens or mammals, including man.

There are five main coccidial species in chickens and there is no cross protection between them. The disease primarily affects young flocks.  The Eimeria multiply in the digestive tract and cause tissue damage.

Coccidiosis is generally acute in onset and is characterised by depression,ruffled feathers and in some cases blood stained diarrhoea.  The severity of the disease depends on the number of oocysts ingested.  The signs can range from mild with depression, decreased growth and feed conversion through to severe with high mortality.