Alternative names:

Giardia infection; Traveler's diarrhea; Giardia lamblia; G Lamblia

What is it?

Intestinal infection caused by a one-celled protozoan restricted to the small intestine and biliary tract. This parasite presents in the trophozoites form, which are active forms living and reproducing themselves in the host, and in the cyst form – the parasite's infecting and resistant forms. Upon ingestion of the cysts, as they pass through the acid environment of the stomach, they are activated and transform into trophozoites

How is it acquired?

Giadia has a worldwide distribution. It can affect 50% of the population in developing countries, particularly in tropical ones. Transmission occurs orally or anally and, therefore, the population at risk are the poor people with bad sanitation, the small children and adults who do not take hygiene measures during sexual intercourse, especially regarding anal sex. Most of the community-based epidemics occurs through contamination of water supplies. Direct contamination occurs through transmission of cysts by touching the mouth with feces-contaminated hands, and indirectly upon ingestion of contaminated food or water. Infected animals, such as dog, cats and cattle. The infecting cysts may remain viable in the environment for months.

What does one feel?

The period from the ingestion of cysts until the onset of the disease ranges from 1 to 4 weeks. Most infections, both in adults and children, are asymptomatic and are characterized only by the elimination of the microorganism. Symptomatic infections may be widespread with a broad range of clinical manifestations, from acute diahrrea with watery feces and abdominal pain to chronic diarrhea, due to malabsorption, which results in a condition called steathorrea (foul-smelling feces, with excess fat, adhering to the toilet bowl) and leads to the development of liposoluble vitamin deficiency and even failure to thrive. Symptoms of diarrhea are due to the toxins produced by giardia, the reaction being attributed to parasite multiplication.

How is the diagnosis made?

The ways whereby the diagnosis can be confirmed range from the identification of cysts or trophozoites in the microscopic examination of feces to the investigation of giardia antigens in the feces or in the aspirated contents of the duodenum. In very specific cases, a duodenal biopsy may be required. When investigating feces for parasites, increasing the sample from 1 to 3, taken in alternate days, may also increase the diagnostic chances from 50% to 90%. Patients with immunodeficiency, such as secretory immunoglobulin A failure, or with cystic fibrosis, turns it into a more severe condition.

How is it prevented?

Hygiene measures, from handwashing to precautions with food purification, especially those that consumed raw, to water filtration and purification of the water distributed, to boiling of non-treated water, to the treatment of infected people and animals, are key in the prevention of the disease.