Parasitary infections remain a very serious health problem worldwide. Giardia lamblia is the most common protozoa known to be responsible for one of the main causes of severe diarrhoea in humans, particularly in immunodepressed people. Epidemiological studies, in 1991, showed that infections with Giardia increased in the United States with a prevalence of around 6% on 178,000 samples. Generally, the disease passes through a short acute phase followed by a chronic phase. Infection by G. lamblia, in the acute phase, is the cause of watery diarrhoea with principally the elimination of trophozoites. The stools become normal again, during the chronic phase, with transient emissions of cysts.
The presence of the parasite on the wall of the duodenal epithelium is responsible for a malabsorption. The disappearance of villosities and their atrophy lead to problems with the digestive process at the level of the duodenum and the jejunum, followed by weight loss and dehydration. The majority of infections remain asymptomatic, however.
The diagnosis of G. lamblia is carried out under microscopy after flotation on zinc sulphate or by direct or indirect immunofluorescence, on non-concentrated samples displayed on a slide. More and more ELISA methods are also now available for the specific detection of cysts and/or trophozoïtes. Detection of this parasite in surface or distribution water can be undertaken by PCR type techniques.
Coris BioConcept has developed a rapid membrane test that can detect Giardia lamblia in non-concentrated faecal samples within 15 minutes. The test is based on the detection of a 65-kDA coproantigen, a glycoprotein that is present in the cysts and trophozoites of G. lamblia.