Cysts may appear to shrink from the cell wall. The cysts are infective as soon as they are passed. Clinical Disease Giardia lamblia colonises the small intestine where the trophozoites adhere to the mucosal surface by means of their sucking disc. Cysts are produced as the parasites descend the intestinal tract although trophozoites can be passed in the faeces in severe infections . G. lamblia is transmitted through ingestion of cysts in contaminated water or food.
Cysts can survive outside the body for several weeks under favourable conditions.
The main symptoms are abdominal pain, flatulence, and episodic diarrhoea with steatorrhea and periodical soreness in severe cases. No blood or mucus is normally seen. What determines susceptibility is poorly understood. After swallowing cysts for the first time, symptoms commonly develop 2-6 weeks later. Laboratory Diagnosis Cysts can be found by examination of the deposit of a formol-ether concentrate of a stool preparation.