Giardiasis or Giardia Intestinal Parasites

Giardiasis is a zoonotic parasitic disease caused by the common intestinal parasite Giardia (also known as Giardia lamlia, Giardia intestinalis, or Giardia duodenalis) most commonly found in food & water that's been contaminated by the droppings of birds and other animals, as well as humans. This microscopic parasite causes diarrhea, weight loss, bloating, nausea, vomiting, and dehydration in humans.


The Giardia parasite infects the intestines of birds, animals, and humans, and is passed back into the food chain via ingestion of infected feces. Giardiasis is often experienced by travelers and people who are otherwise exposed to fecal-contaminated food and drink, including swallowing water when swimming in lakes, ponds, rivers, streams, as well as some swimming pools. Giardia parasites are easily passed into the food chain much like a bacteria or virus, such as on contaminated door knobs.

Birds and other animals with the parasites can easily spread onto food sources through air conditioners and vents, so proper pest control methods must be taken to prevent contamination, especially at restaurants, food processing plants, or anywhere humans consume food or drink. Giardia can also spread through bodies of water if swallowed while swimming, so care ought to be taken in lakes, rivers, streams, and public swimming pools. Since birds are naturally drawn toward bodies of water, including ducks, geese, and many others, they are frequently to blame for Giardia water contamination.

Think it Couldn't Happen?

In 2013, a Giardia outbreak was reported in Niagra Falls when a swimming pool was contaminated1. At least 18 people were confirmed to be contaminated by the Giardia outbreak, while 50 others were under investigation.

The CDC regularly reports outbreaks of Giardiasis in the United States, available on their website at

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