Final answer:
Giardia lamblia, the organism causing giardiasis, attaches to the intestinal wall and causes edema (swelling) in the surrounding tissue due to inflammation and damage to the intestinal villi.
Step-by-step explanation:
The protozoan Giardia lamblia, which causes the intestinal disease giardiasis, attaches to the epithelium wall where they actively feed, resulting in edema (swelling) in the surrounding tissue. Giardia lamblia uses an adhesive disc to adhere to the intestinal mucosa and does not invade the intestinal cells directly. It causes damage to the intestinal villi and inflammation, leading to impaired nutrient absorption and symptoms like severe diarrhea.