ABSTRACT
Coccidia are among the most important parasites of animals, and they were the first protozoa discovered. The oocyst is the key stage of all coccidians, and their classification was based on the number of sporozoites and structure of the oocyst. The host becomes infected by ingesting sporulated oocysts of Eimeria. Oocysts are produced after fertilization and are passed in feces in a noninfective unsporulated stage. Sporulation occurs outside the host and oocyst become infectious. The tachyzoite consists of various organelles and inclusion bodies including a pellicle, cytoskeleton, secretory micropore, a mitochondrion, endoplasmic reticulum, a Golgi complex, ribosomes, rough and smooth endoplasmic reticula, nucleus, acidocalcisomes, amylopectin granules, Golgi apparatus, and an apicoplast. The nucleus is usually situated toward the central area of the tachyzoite. It is nearly spherical with an anterior concavity.
