Final answer:
Giardia is transmitted through water as resistant cysts that are dispersed and survive cold temperatures and chlorination. These cysts develop into trophozoites in the small intestine, leading to gastrointestinal symptoms.
Step-by-step explanation:
Giardia is transmitted as cysts that are dispersed through water. These cysts are resistant to cold temperatures and chlorination and must be filtered out of municipal water supplies to prevent transmission.
Giardiasis, the type of gastroenteritis caused by Giardia lamblia, is a waterborne illness that can also be spread through contaminated food or from person to person, especially in day-care centers or between children.
Once ingested, these cysts develop into the active form known as trophozoites, which attach to the lining of the small intestine, blocking nutrient absorption and often causing diarrhea and abdominal pain.