Giardiasis (Giardia lamblia):An enteric pathogen, Giardia has a huge impact on global health by causing diarrhea and exacerbating malnutrition, particularly in children. This pathogen causes chronic symptoms even in immune competent individuals and can be difficult to eradicate with currently available treatments. As a threat to public water and food supplies, Giardia is listed as a category B Biodefense agent..