Coccidiosis is caused by a protozoa – a single-celled organism – of the species Eimeria (also known as Isospora). Members of all orders of reptiles can harbour coccidian parasites.
Coccidiosis is spread through contamination with faeces – the coccidiosis parasites reproduce in the intestines and create infective eggs, which are passed out ready to infect the next animal. Young reptiles, and breaded dragons in particular, are especially susceptible to developing signs of an infection.
A subspecies of coccidiosis is cryptosporidium, which can also be seen in reptiles.