A Microbiological Overview of the Intestinal Parasite Giardia Lamblia

Giardia is the most prevalent protozoal infection in the human intestines.   By its nature, it aggressively causes an infection in about 75 % of those exposed. It manifests itself with abdominal bloating, flatulence, nausea, vomiting and fatigue. It has been estimated that up to 2.5 million cases of Giardiasis occurs each year in the USA. There are as many as 20% of the world’s population who are chronically infected.


Often Giardia Lamblia is known as the travelers disease. Commonly acquired in areas where there is poor sanitation and where there is contaminated water, streams and ponds. It may also be passed on through contaminated food.

This parasite has a life cycle of only two stages. The cyst { trophozoite} which is ingested by the unfortunate victim and the cyst that is expelled and passed on into the environment waiting to recycle itself. The inactive cyst can live outside the body for long periods of time. Once the parasite is ingested it quickly lodges itself in the intestine and rapidly multiplies, doubling in 9-12 hours. As many as 15 % of those who are infected have mild symptoms or none at all. The infection can be self limiting. However, 50 % of those infected can have a chronic form ,with diarrhea and malabsorption problems and the potential for weight loss.

In developing countries Giardia Lamblia is a common cause of chronic diarrhea and growth retardation in children. Less developed countries such as the Soviet Union, Mexico, Southeast Asia and Western South America often have inadequate water treatment facilities.

Children in day care centers and senior nursing homes have the greatest risk for outbreaks of Giardia Lamblia because of the increased potential for fecal-oral contamination. The sharing of personal items or eating utensils, and individuals who practice anal/oral sex are at greater risk.


A diagnosis can not be made with only a physical examination by your physician. It is necessary to collect a stool specimen to check for this ovum and parasite. Infected people are at risk for spreading this infection. Precautions with good hygiene practices are usually adequate in the home environment. Those in hospitals or public institutions should be isolated to prevent transmission.


Comprehensive antibiotic therapy is standard in the treatment of Giardiasis and it is usually responsive. There is a risk of reinfection. At the completion of treatment a stool specimen may be needed to confirm that there is no longer any sign of Giardia.

Your health care provider should provide you with information that reinforces appropriate hygienic methods. A physician may give you a prescription for an antibiotic to be used when traveling. With personal observations as to early signs and symptoms,this allows you to begin treatment early if needed.

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