Giardiasis: Diagnosis

Diagnosis is quite difficult due to the intermittent character of the presence of Giardia in the faeces. The diagnosis is mainly based on fresh or enriched coprological preparations. Sometimes several analyses of faecal specimens are needed. One specimen gives a detection rate of approximately 70% while 3 specimens increase this rate to approximately 85%. Generally cysts are found, rarely trophozoites. Other techniques such as duodenal aspiration or the EnteroTest (the string test) are less practical. In rare cases infections have been recognised on jejunal biopsy material or mucus sampled during endoscopy. Recent techniques for detecting antigen in faeces have proved sensitive, specific and fast. One means by which antibodies to Giardia can be detected is immunofluorescence, but this is not specific or sensitive.

Microscopically a differentiation needs to be made with other flagellates such as the commensal Chilomastix mesnilii, Enteromonas hominis, Trichomonas hominis (= Pentatrichomonas hominis) and Retortamonas intestinalis.

The histological intestinal lesions are not very pronounced: flattening of the intestinal villi, lymphocytic infiltration of the mucosa, no ulceration. Persons with hypogammaglobulinaemia have more pronounced histological lesions and the clinical consequences are more important, with steatorrhoea, persistent infection, resistance to treatment. Radiology of the small intestine is aspecific. If giardiasis is suspected, but cannot be proven, a trial therapy can sometimes be used.

Category: Medicine Notes