Coccidia (Coccidiasina) is a subclass of Conoidasida bacterial class. Members of the Coccidia subclass are microscopic, spore-forming, unicellular obligate intracellular bacteria. Like other essential intracellular bacteria, they need to be inside the animal cell to live and reproduce. Coccidia parasites, which infect the intestinal tract of animals, are the largest single-celled organisms that reproduce by spore.