Life Cycle of Giardia Lamblia

Giardia lamblia is a single celled, protozoan flagellate that can infect the intestinal tract of humans, causing severe diarrhea, abdominal pain, bloating, nausea and vomiting. Malabsorption problems may also result from chronic cases of giardiasis.

Distribution

• Giardia lamblia occurs in warm climates throughout the world. It is common among children, who are more likely to place contaminated items in their mouths. It is the most common parasitic infection in the United States.

Cyst Stage

• Giardia cysts will pass through the digestive system of a host, eventually being eliminated in stool. Cysts may then inadvertently contaminate food, water or other items, continuing to survive for months. These cysts may eventually be eaten by a host. Trophozoites, the mobile form of the parasite, can also be passed in the stool, but will not survive outside the host.

Trophozoite Stage

• Once eaten, a cyst will open within the small intestine and release two trophozoites. These will then reproduce through binary fission in the small intestine. They will then either swim freely within the intestines or attach to the wall of the intestine with a ventral sucker.

Encystation Stage

• As the trophozoites move through the intestinal tract toward the colon, they form cysts as a means of protection. These will be eliminated in the stools of the host. At this stage, the cysts can infect another host by contaminating food, water or other items that come in contact with the mouth of the host.

Diagnosis and Treatment

• Diagnosis is done by searching for cysts and trophozoites in a recently collected stool specimen. Duodenal fluids samples or duodenal biopsies may also be revealing. Antigen blood tests can also help in the diagnosis. The drugs of choice for treating a giardia lamblia infection are metronidazole and tinidazole.

Prevention

• Giardiasis is simple to prevent by avoiding contaminated water, food or other items. Boiling water that may be contaminated prior to drinking can effectively prevent the disease. Washing fruits and vegetables that will be consumed raw or cooking food items will also minimize the risk of infection.