Original: Giardia lamblia (synonymous with Lamblia intestinalis and Giardia duodenalis) is a flagellated protozoan parasite that colonises and reproduces in the small intestine, causing giardiasis.
Simplified: Giardia lamblia (synonymous with Lamblia intestinalis and Giardia duodenalis) is a flagellated protozoan parasite that infects the gastrointestinal tract and causes giardiasis.