What is the main etiology of Giardia lamblia?

Giardia lamblia is classified as a protozoan parasite, which is why it falls under the parasitic etiology. This organism causes giardiasis, an intestinal infection characterized by diarrhea, abdominal pain, and gastrointestinal discomfort. Its life cycle includes a cyst stage, which is highly resistant to environmental conditions and can survive in water for extended periods. Transmission occurs primarily through the ingestion of contaminated water or food, leading to infection in humans and other animals.

The other options involve different types of pathogens. Viral infections are caused by viruses, which are much smaller and replicate differently than protozoan parasites. Bacterial infections involve bacteria, single-celled organisms that can also cause a range of diseases but differ fundamentally from parasites like Giardia. Fungal infections are due to fungi, which are a distinct group of organisms that also do not include protozoa. By identifying Giardia lamblia as a parasitic organism, it helps clarify the nature of infections it can cause and the appropriate measures needed to prevent and treat such infections.