A specific parasite cause the infection. Giardia cysts are a form of the parasite that survive outside of humans and animals. The cysts spread the infection. You can get it by swallowing the cysts. It grows once it gets to the small intestine. It can pass to you from water, food, or stool that have the cysts. Examples include:
Eating food, drinking water, or swimming in water that have the cysts
Contact with a person's hands contaminated by human or animal stool
Oral to anal contact during sex
Giardiasis spreads easily. It takes only 10 cysts to cause infection.
Giardiasis. Kids Health—Nemours Foundation website. Available at: ...(Click grey area to select URL) Updated August 2017. Accessed May 29, 2018.
Giardiasis. Merck Manual Professional Version website. Available at: https://www.merckmanuals.com/professional/infectious-diseases/intestinal-protozoa-and-microsporidia/giardiasis. Updated February 2017. Accessed May 29, 2018.
Parasites–giardia. Centers for Disease Control and Prevention website. Available at:
https://www.cdc.gov/parasites/giardia. Updated July 22, 2015. Accessed May 29, 2018