Infectious Disease Compendium



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.

Epidemiologic Risks

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.

Albendazole 400 mg/day for 5 days, was comparable metronidazole with fewer side effects (PubMed).

In failures, quinacrine may work (PubMed) as well as nitazoxanide, paromomycin, quinacrine, and furazolidone.


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.

Curious Cases

Relevant links to my Medscape blog

The Curves Continue to Diverge

Last Update: 05/01/18.