Life History/Reproduction

Life CycleGiardia lamblia exists in two stages; trophozites which is the active stage living in a host, and cysts; the non-active stage found in the environment, each encompassing two trophozites (Buret 2007). Cysts have been found to survive in water sources for months even in cold temperatures (idph). These environmentally resistant cysts are found in 80% of water from outdoor sources such as lakes, streams, and ponds, as well as 15% of filtered water (Robertson et al 2007). These cysts can be transmitted in multiple ways such as digesting contaminated water or food, direct fecal-oral contact, or any sexual acts involving the anus, only needing about a dozen of these cysts to cause an infection (Tessier & Davies 1999). Once in the stomach they undergo a process by the name of excystation, which breaks down the cysts walls and produces the active version, trophozoites (CDC). Trophozites use the sucking disk on the side of their body to attach to the villi of the small intestine where they reproduce by binary fission (Erlandsen, p.334). The trophozites continue down the intestinal track and go through the process of encystation, becoming cysts once again, once they reach the colon. These cysts contaminate any feces passed, and the cycle repeats itself (CDC).


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