The disease is caused from the inhalation of mold spores that may be present in the environment. The main type of spores are from the genus Aspergillus though other mold species can cause the disease as well.
Severely affected chicks are most easily distinguished as their condition deteriorates. They will begin to have trouble standing, may fall repeatedly, and eventually will lay prone on their side unable to get up.
Coccidiosis is one of those diseases that, although prevalent in poultry, is almost entirely preventable with the use of either a vaccine or medicated feed (but never both).