Cysts of this flagellated organism survive in water; when ingested, the trophozoite grows in the intestine, causing diarrhea.

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Identify the key characteristics described: the organism forms cysts that survive in water, is flagellated, and its trophozoite stage grows in the intestine causing diarrhea.

Recall common flagellated protozoan parasites that have a cyst stage and cause intestinal infections, such as Giardia lamblia.

Understand that cysts are the infectious form that can survive outside the host, especially in water, facilitating transmission.

Recognize that once ingested, the cysts transform into trophozoites in the intestine, where they multiply and cause symptoms like diarrhea.

Conclude that the organism described is likely Giardia lamblia, a flagellated protozoan known for waterborne transmission and causing giardiasis.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Life Cycle of Flagellated Protozoa

Flagellated protozoa often have two main stages: the cyst and the trophozoite. The cyst is a dormant, resistant form that survives harsh conditions like water exposure, while the trophozoite is the active, feeding stage that multiplies in the host's intestine, causing symptoms such as diarrhea.

Transmission and Infection Route

Ingestion of cysts through contaminated water is a common transmission route for intestinal flagellates. Once inside the host, cysts excyst to release trophozoites, which colonize the intestine and lead to infection, highlighting the importance of water sanitation in preventing disease.

Pathogenesis and Clinical Manifestations

The trophozoite stage of flagellated protozoa causes intestinal damage or disrupts absorption, resulting in diarrhea. Understanding how the organism causes disease helps in diagnosing and managing infections, often involving symptoms like watery stools and abdominal discomfort.

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