Eimeria is a genus of single-celled parasites known as coccidia, primarily affecting the intestines of various animals, including birds and mammals. These parasites are responsible for a disease called coccidiosis, which can lead to severe gastrointestinal issues, especially in young or immunocompromised animals. The life cycle of Eimeria involves multiple stages, including oocyst formation, which is the infectious form that can survive outside the host. Transmission typically occurs through contaminated food or water, making sanitation crucial in preventing outbreaks, particularly in livestock and poultry farming.