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Giardiasis Generalities, Risk Factors Causes And Transmission

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Giardiasis  is a disease caused by the infestation with the intestinal parasite Giardia lamblia (also called Giardia intestinalis). Symptoms of giardiasis are diarrhea, abdominal cramps, flatulence and overall intestinal symptoms. Giardiasis symptoms in children are represented by growth and weight gain failure. Symptoms of giardiasis may occur only once for a short period of time or may come and go for a longer period of time. Even if the symptoms are not present the parasitic infestation may still exist.



 Areas endemic for Giardia

Giardia occurs in all parts of the world, but is a very important problem in areas where access to water is limited or where the rules of hygiene are poor. In the U.S. G. intestinalis is found in water such as rivers, streams or lakes (surface water sources).    Giardia outbreaks are present where there is no adequate treatment of urban water systems or in areas where water was contaminated with sewage discharges. Swimming pools, fountains and lakes in parks that are not treated properly and maintained to that standard or do not have a suitable filtration system may also be constant sources of infection.

Cases of infection are frequent in kindergartens and care centers, mainly due to poor hygiene such as washing hands. In some care centers more than 35% of children had Giardia in the stool (feces). Most cases of infection occur in mountainous areas, because people do not realize that the parasite can survive at low temperatures like those of mountain lakes and rivers, so untreated water is commonly consumed. The disease is more common in communities that use water from rivers and lakes that supply drinking water and do not use water purification processes.

Giardiasis Risk Factors

Children are infected more frequently than adults, especially those in orphanages, where children are not taught to use the toilet properly. It is also most common infection in care homes for the elderly, especially those with urinary incontinence (loss of urine).  Chlorination of drinking water is not a reliable method of destroying the parasite. Those who go camping and hikers who travel in areas where water may be contaminated with the parasite, have a higher risk of contracting the disease, given that they do not purify their water by boiling or filtering.

Giardiasis Causes

Giardiasis (also called giardia) is produced by a single-celled parasite called Giardia lamblia, Giardia intestinalis or Giardia duodenalis. The parasite lives and multiplies in the human or animal intestine. Once in the intestine, it attaches to the intestinal mucosa, changes its normal function and competes for important nutrients.



This causes the following symptoms:

  • Discontinuities in intestinal mucosa may make the intestine to be less able to absorb nutrients from food that is passing through the gut. If not absorbed, nutrients remain in the intestinal tract, causing diarrhea, cramps and flatulence (very often associated with giardiasis)
  • Parasite can accelerate the passage of food through the intestine, causing diarrhea. The stool of infected animals or humans contain parasites. Giardia lamblia infestation occurs in two ways:
  1. Hand-mouth contact which transfer the parasite from the stool of infected persons. This happens due to poor hygiene, such as lack of hand washing. The parasite can be transferred through direct contact and oro-anal or oral-genital contact with an infected person
  2. Indirect transmission of the parasite by consuming water or food that came into contact with contaminated faeces.

The incubation period lasts 7-10 days but can range from 3 to 25 days or even more in some cases. Giardiasis is contagious as long as the parasite is present in faeces, which can take several months. Not all infected individuals have symptoms, but a person who has no symptoms can still spread the disease .

Giardiasis Transmission

A person can become infected with this parasite when eating contaminated products or drinking contaminated water. For example if you change the diapers of a child with Giardia and not Wash hands after any or anyone that is reached will be infected.  Once giardia enters the body, it multiplies in the small intestine and spread in the large intestine. Some parasites form cysts, inactive forms that can survive for a longer period of time outside the body in harsh conditions. Cysts and parasites leave the body through the stool and contaminate water or food, continuing the parasitic life cycle.