A flagellated (it has a flagella, it doesn't beat itself with a whip) protozoa. G. lambia is the human pathogen, every animal has its own Giardia.
Water born, food born, and person to person. Many wild animals carry Giardia. Camp, drink the fresh water, get diarrhea. There are day care outbreaks. And swimming pools; kids use pools as a toilet (PubMed).
1-2 week incubation period. Watery diarrhea, often prolonged, with bloating, gas and malabsorption.
Hypogammaglobulinaemia can result in chronic infection (PubMed).
Metronidazole for seven days.
As a small bowel pathogen, it can be hard to find once it passes to the large bowel. It is the reason for O&P x 3.
It is a cause of lactose intolerance after infection.
Relevant links to my Medscape blog
Last Update: 05/01/18.