Giardia Or Lamblia

By Author: Sulamita Berrezi
Total Articles: 115
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This organism is a common parasite of the human gastrointestinal tract and is found in all parts of the world. Although its prevalence is greatest in developing countries where hygiene facilities are poor, outbreaks of giardiasis continue to occur in many developed countries. It has a simple life history. The trophozoite (the active form in the intestine) lives in the duodenum and jejunum of the host where it attaches to the enterocytes by means of a ventral disk. It reproduces rapidly by mitotic division and in heavy infections can cover large areas of the mucosa. Some trophozoites encyst; a protective wall forms around the organism, and the cysts pass out in the feces. Cysts are directly infective and after ingestion by a new host, the organisms emerge to establish a new infection. Disease can follow the ingestion of as few as 10 cysts which, given moist conditions, are viable for several months. In developed countries, most infections can be traced to contaminated water, but direct personto- person transmission has been documented. In developing countries, poverty-related unsanitary conditions and inadequate disposal of feces ...
... promote oro-fecal spread of the parasite, but contaminated water is also likely to be important. The large number of cyst-producing individuals with asymptomatic infection constitutes a reservoir of G. intestinalis. In addition, some animals are known to harbor Giardia and may be a source of human giardiasis. Infection with G. intestinalis can be associated with a wide range of symptoms: from mild, selflimiting watery diarrhea to persistent foul-smelling diarrhea with vomiting, abdominal pain and distension, and a severe malabsorption syndrome. However, many infected individuals (from 20 to 84% of infected cases) remain asymptomatic. It is not clear why the parasite can cause such a range of degrees of illness. The nutritional impact varies with both the severity and duration of the symptoms. In the early stages, anorexia is of major importance, but if the disease persists, intestinal aspects compound the situation. In at least 50% of symptomatic patients there is malabsorption of fat, carbohydrates, protein, and micronutrients (particularly vitamin A) associated with structural and functional abnormalities in the small intestine. Damage to the mucosa can range from little to subtotal villus atrophy, but most subjects have mild villus shortening and increased crypt depth. The abnormalities are associated with a reduction in disaccharidases, notably lactase activity and in lowered intraluminal concentrations of the hydrolytic enzymes trypsin, chymotrypsin, and lipase. The small intestinal barrier function is compromised, allowing translocation of potentially antigenic macromolecules into the body with consequent stimulation of the immune and inflammatory mechanisms resulting in growth retardation. Little is known about the nutritional effects of nonsymptomatic giardiasis.