Giardiasis is one of the most widespread parasitic diseases that is present not only in developing countries but in the developed countries as well. Giardiasis can cause both endemic and epidemic intestinal disease and diarrhea. The causative agent of Giardiasis is the cosmopolitan protozoan parasite, Giardia lamblia which colonizes the small intestines of humans; it is also present in other mammals (Fauci, et al. , 2008). Infection follows the ingestion of very resistant cysts, which enables the organism to survive even through harsh environmental conditions.
These will excyst or “hatch” in the small intestines releasing the flagellated trophozoites, which increases in number and proliferate through binary fission. The trophozoites may remain free in the lumen of the intestines or it may attach to the mucosal epithelium. As the trophozoite encounters an unfavorable condition, it again forms a morphologically distinct cyst and passes into the feces. Trophozoites are the dominant stage found in patients with loose or watery stools.
However, it is the resistant cyst that is able to survive outside its human host and is the form responsible for infection (Fauci, et al. , 2008). Figure 1 describes the life cycle and mode of transmission of Giardia lamblia that involves human host. Ingestion of as few as 10 cysts was said to be adequate to initiate infection in humans. Since the cysts form is the potentially infectious form when excreted and then ingested, the person-to-person mode of spread of the disease is common when fecal hygiene is poor.
The prevalence of Giardiasis, both symptomatic and asymptomatic cases, was found to be very high in day-care centers where there are high risk for anal-oral contact (Black, Dykes, Sinclair, & Wells, 1977) and other institutional settings that have poor fecal hygiene. Waterborne transmission was responsible for episodic infections, which frequently happen to campers and travelers. Waterborne transmission was also highly implicated for the major epidemics in various metropolitan areas as well. In the United States, Giardia is commonly involved in epidemics of gastroenteritis (Fauci, et al.
, 2008). In 2004, case reports of Giardiasis in the United States increased by 4. 4% from 20,084 in 2003 to 20,962 (Yoder & Beach, 2007). Surface water from the mountain streams to the large municipal reservoirs can be a vehicle for transmission of Giardia cysts. Also, leaking water pipe system could be a route for the spread of Giardiasis due to sewage contamination. The efficacy of water as a vehicle for spread of disease is enhanced by the prolonged survival of its resistant cyst (Fauci, et al. , 2008).