Giardia lamblia

Giardia lamblia is an intestinal parasite of vertebrates. The feeding stage, called a trophozoite is teardrop shaped, binucleate, with 4 pairs of flagella and has pair of ventral sucking discs that allow it to adhere to the epithelial cells of the intestine. Transmission is by contaminative ingestion of the cyst, which excysts in the duodenum. The trophozoites divide by binary fission and huge numbers can build up. It is estimated that a single diarrheic stool contained 14 billion parasites. This parasite cannot survive outside of the body as a trophozoite and so must encyst. Only trophozoites are present in small intestine and in the diarrheic watery stool. As faeces enter the colon and begin to dehydrate, the trophozoite becomes encysted. Newly formed cysts have 2 nuclei, older cysts have 4. The life cycle is completed when the cyst is ingested.

So many parasites may be covering the epithelial cells of the intestine that absorption of nutrients is physically blocked especially interfering with the absorption of fats. Although most cases are asymptomatic, in disease cases there is diarrhea, dehydration, intestinal pain, flatulence, and weight loss and increased mucous production in the intestine. The stool is "fatty" but never bloody. The gall bladder can become infected leading to jaundice. It is not fatal but can be extremely discomforting.

Giardia lamblia trophozoite

Giardia lamblia early cyst

Giardia lamblia late cyst

Giardia lamblia cyst

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