Giardiasis is an intestinal infection caused by a microscopic parasite called Giardia lamblia. This parasite is often found in contaminated water, food, or surfaces, and it can spread through person-to-person contact. Symptoms of giardiasis may include diarrhea, abdominal cramps, bloating, and nausea, which can last for several weeks if untreated. Diagnosis typically involves testing stool samples to identify the presence of the parasite. Treatment usually includes medications that target the infection. To prevent giardiasis, it is important to practice good hygiene, such as washing hands regularly and drinking clean, treated water.