What does oocyst mean?
An oocyst is a specialized, resistant cyst formed by certain parasitic protozoans, particularly coccidia. It contains sporozoites, the infective stage of the parasite, and is commonly produced in the host's intestine before being released in feces. Its protective wall allows it to survive outside a host, making contaminated soil, water, food, or bedding potential sources of infection. The term is important in veterinary and human parasitology, including the study of diseases caused by organisms such as Cryptosporidium and Eimeria. Although “oo-” refers to an egg or egg-like structure, an oocyst is not an animal egg cell: it is a cyst containing many parasitic organisms at an infective stage. The word is most often used with terms such as “infective,” “sporulated,” and “shedding.”
nounA thick-walled, resistant cyst containing the infective sporozoites of certain parasitic protozoans, especially coccidia, usually formed in the host's intestine and released in feces.
- A thick-walled cyst containing the infective stage of a parasitic protozoan, especially a coccidian.
"The oocyst remains viable in the soil until an intermediate host ingests it."
"Microscopic examination of the stool sample revealed parasites in the form of oocysts."
"The resistant oocyst can remain infectious in contaminated soil for an extended period."
The standard plural is formed by adding -s; “oocyst” is unchanged in the singular.
"The laboratory detected oocysts in samples collected from the infected animals."
An oocyst is a microscopic time capsule: its tough wall helps a parasite survive outside its host and wait to be swallowed by another.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does oocyst come from?
The word combines the combining form oo-, from Greek ōion meaning “egg,” with cyst, from Greek kystis meaning “bladder” or “sac.” The compound was coined in the late 19th century to describe the egg-like resistant stage of certain parasitic protozoans. Its components also appear in modern scientific words such as oocyte, ovum, and cystic.
Related word forms
How oocyst is actually used
This is a technical biological term, chiefly used in parasitology, veterinary medicine, and microbiology. It is distinct from a generic cyst and from an oocyte, the immature egg cell of an animal.
Easily confused with oocyst
An oocyst is a protective cyst containing parasitic sporozoites, whereas an oocyte is an immature female egg cell that develops within an ovary.