Coccidia (Coccidiasina) are a subclass of microscopic, spore-forming, single-celled obligate intracellular parasites belonging to the apicomplexan class Conoidasida.

Coccidian parasites infect the intestinal tracts of animals,[2] and are the largest group of apicomplexan protozoa.

An exception is Toxoplasma gondii, which can infect all mammals, although it can only undergo sexual reproduction in cats.

Depending on the species of coccidia, infection can cause fever, vomiting, diarrhea, muscle pain, and nervous system effects and changes to behavior, and may lead to death.

[3] Coccidian infections display symptoms mainly from the digestive tract including diarrhea, inflammation, intestinal pain or damage, vomiting, and irregular nutrition.

These can lead to weight loss or reduced growth development, anemia, exhaustion, and even death in severe cases.

Coccidiosis is most commonly treated through the administration of coccidiostats, a group of medications that stop coccidia from reproducing.