microscopic view of giardia intestinalis a protozoan parasite that causes giardiasis

parasite protozoan giardia giardiasis infection waterborne cysts symptoms diarrhea nausea vomiting abdominalpain fever fatigue microscopic organism illness disease health medical science biology microbe microorganism tiny small invisible hidden danger risk spread transmit contaminate water food soil animals humans children adults elderly immunesystem compromised weak vulnerable healthcare treatment medication view intestinalis causes