[Giardiasis in children. Ultrastructural study of the parasite]

Giardia lamblia is the first protozoan to be identified and recognized as an important pathogen in human disease. We studied 8 pediatric patients with giardiasis in order to examine the clinical spectrum, the structural changes of the small intestinal mucosa and mainly the protozoan's ultrastructural features. The most common clinical manifestations were diarrhea, abdominal pain, anorexia, vomiting, failure to thrive. Infection was confirmed by excreted cysts in the stools in one patient, by the presence of trophozoites in duodenal aspirate and on jejunal mucosa. Giardiasis was not associated with hypogammaglobulinemia in our patients and no or only slight mucosal abnormalities were present in jejunal biopsies, except one which showed a flat mucosa. Specimens for transmissions and scanning electron microscopy were taken. We could establish the protozoan's features, its normal distribution, its relationship to intestinal mucosa and structural indications of the normal reaction of intestine with the use of ultrastructural techniques. The trophozoites colonized the proximal intestine, adhered to microvilli of columnar cells near the bases of villi, wedged or lodged in mucus. The sticky mucus producing an effective diffusion barrier to nutrients could explain malabsorption phenomena. Numerous intraluminal lymphocytes were seen, suggesting an immune response. These observations indicate that in giardiasis the clinical spectrum and structural changes of the small intestinal mucosa vary widely, suggesting a different reaction of immune system and/or a different degree of infection.