Pathophysiology of enteric infections withGiardia duodenalis

Abstract

Summary :Giardia is the most prevalent human intestinal parasitic protist in the world, and one of the most common parasite of companion animals and young livestock. Giardia is a major cause of diarrhea in children and in travelers. The host-microbial interactions that govern the outcome of infection remain incompletely understood. Findings available to date indicate that the infection causes diarrhea via a combination of intestinal malabsorption and hypersecretion. Malabsorption and maldigestion mainly result from a diffuse shortening of epithelial microvilli. This enterocytic injury is mediated by activated host T lymphocytes. Pathophysiological activation of lymphocytes is secondary to Giardia-induced disruption of epithelial tight junctions, which in turn increases intestinal permeability. Loss of epithelial barrier function is a result of Giardia-induced enterocyte apoptosis. Recent findings suggest that these effects may facilitate the development of chronic enteric disorders, including inflammatory bowel disease, irritable bowel syndrome, and allergies, via mechanisms that remain poorly understood. A newly discovered SGLT-1 glucose uptake-mediated host cytoprotective mechanism may represent an effective modulator of the epithelial apoptosis induced by this parasite, and, possibly, by other enteropathogens. A better understanding of the pathogenesis of giardiasis will shed light on new potential therapeutic targets.

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“…The intetstinal changes scanned by the electron microscopy came in agreement with other reports on Giardia [7,34]. Such changes ensured that the colonization of the intestine with Giardia trophozoites caused diffuse destruction in the microvillus brush border which in turn resulted in maldigestion and malabsorption effects.…”

“…Giardiasis outbreak in sheep mostly showed no clinical sign or mortality, but Giardia-infected lambs had malabsorption, decreased weight gain, and reduced feed efficiency [5]. The pathophysiological changes associated with Giardia infection include: malabsorption of electrolytes and nutrients, intestinal microvillus atrophy, loss of epithelial barrier function due to the produced ulceration and infarction , increased permeability and narrowing of the lumen [6,7]. The Changes in the sero-biochemical constituents and the hypothesis of decreased activity of the defense system for protecting tissues from the free radical damage associated with Giardia infection in lambs need further investigation.…”

Increased levothyroxine requirement in a woman with previously well-controlled hypothyroidism and intestinal giardiasis

“…The presence of trophozoites activates intestinal T lymphocytes, which induce inflammatory epithelial damage, shown by diffuse shortening of mi-crovilli, maldigestion and malabsorption. In addition, Giardia disrupts epithelial tight junctions and induces enterocitic apoptosis resulting in loss of epithelial barrier, increased intestinal permeability, and diarrhea (10,15). Similar chronic malabsorptive syndromes related to mucosal inflammation have been described with other common intestinal infection agents such as Strongyloides, Clostridium difficile, and Cryptosporidium (16).…”

“…Giardia lamblia is the most prevalent human intestinal parasitic protist (10). Giardiasis is probably subdiagnosed, but it affects 5%-29% of Brazilian children, more commonly in environments with poor sanitary conditions (11)(12)(13).…”

Secnidazol Treatment to Improve Milk Yield in Sheep with Giardiasis

“…On day 10, after (Buret, 2008). Therefore alterations in association with the gastro-intestinal system finally accompany decreased weight gain and to an altered feed efficiency (Olson et al, 1995;Sweeny et al, 2010), resulting with decrased milk yield.…”