Giardiasis etiology: what causes it

Giardia lives in the intestines and leaves the body in stool. If microscopic forms from stool reach the mouth, they can start an infection. Common routes include drinking untreated or contaminated water, eating food handled with unwashed hands, touching contaminated bathroom surfaces, and close contact with an infected person. Swimming water can also be a source when it is swallowed.

The infection may lead to watery diarrhoea, abdominal cramps, bloating, gas, nausea, and fatigue. Symptoms can be absent, mild, or prolonged. See [Giardiasis](/conditions/giardiasis/) and [Bloating](/symptoms/bloating/) for related explanations.

Use safe drinking water, wash produce with safe water, and clean your hands with soap and water after toilet use and before eating. Avoid swallowing pool or natural water. If you have diarrhoea, avoid preparing food for others and clean shared bathroom surfaces. Arrange a [GP Consultation](/treatments/consultations-and-assessment/gp-consultation/) if symptoms follow a possible exposure or do not settle. Treatment may include prescribed [Antibiotic Treatment](/treatments/medical-management/antibiotic-treatment/), depending on assessment.

Contact a clinician for ongoing diarrhoea, recurrent symptoms, dehydration, or unexplained weight loss. Seek urgent help for severe abdominal pain, fainting, confusion, blood in stool, or inability to keep fluids down. Get advice earlier if the affected person is a baby, older adult, pregnant, or living with reduced immunity.

Ask which exposure is most relevant, whether stool testing is needed, how to prevent spread at home, and which treatment is appropriate if Giardia is confirmed.