E. acervulina and E. maxima develop in epithelial cells within the small intestine and generally cause chronic intestinal coccidiosis. The most easily recognized clinical sign of severe cecal coccidiosis is the presence of bloody droppings. Dehydration may accompany cecal coccidiosis. Coccidiosis caused by E. tenella first becomes noticeable at about three days after infection. Chickens droop, stop feeding, huddle together and by the fourth day blood begins to appear in the droppings.
Mortality is highest between the fourth and sixth days.
Death may occur unexpectedly, owing to excessive blood loss. Birds that recover may develop a chronic illness as a result of a persistent cecal core. However, the core usually detaches itself by eight to ten days and is shed in the droppings. E. necatrix causes a more chronic disease than E. tenella and does not produce as many oocysts. Therefore, a longer time is usually required for high levels of environmental contamination.