Explore the recorded discovery and history of Giardia duodenalis, with source links and stated limits.
An intestinal protozoan with a flagellated feeding form and a separate cyst form. Infection may be asymptomatic or cause diarrheal illness.
The selected sources do not establish the first person ever infected. Naming, recognition and biological origin are separate questions.
Source check: 2026-09-21. Educational content; independent scientific review remains pending.