Copyright ©2013 Baishideng Publishing Group Co.
World J Gastroenterol. Dec 21, 2013; 19(47): 8974-8985
Published online Dec 21, 2013. doi: 10.3748/wjg.v19.i47.8974
Table 1 Main pathophysiological effects of Giardia duodenalis and their mechanisms
Giardia-induced pathophysiological responsesMechanisms involved or hypothesized to be involvedSelected references
Intestinal epithelial cell apoptosisInduction of pro-apoptotic factors: Caspase-3, 8 and 9, Inhibition of anti-apoptotic factors: poly (ADP-ribose) polymerase (PARP) cleavage[10,18,19,21,23]
Halt of enterocyte cell-cycle progressionNutrient competition (arginine), up-regulation of cell-cycle genes[25]
Intestinal barrier dysfunctionDisruption of claudin-1 and alpha-actinin by unknown mechanisms, caspase-3 mediated disruption of zonula-occludens (ZO)-1, myosin light chain kinase-mediated disruption of F-actin, and ZO-1[10,17,19,21,26,27,29,30]
Small intestinal hypermotilityAdaptive immunity, neuronal nitric oxide, mast cell degranulation[118-120]
Diffuse shortening of brush border microvilliCD8+ lymphocytes - mediated via parasite secretory/excretory products[13,16,21,31]
Crypt hyperplasiaAlteration villus/crypt ratio[21,62,99]
Microbiota compositionMicrobiota from infected host may become pathogenic[14,33]
Increased mucus productionIncreased mucus secretion in response to the parasite[66]
Brush border enzyme activity deficienciesLoss of surface area (microvilli and villi)[16,21,98,121,122]
Disaccharidases deficienciesLoss of surface area (microvilli and villi)[10,16,99,122]
Electrolyte/nutrient/water malabsorptionLoss of surface area (microvilli and villi)[10,19,21,62,99,123]
Anion hypersecretionUnknown mechanisms[10,19,99]
Table 2 International reports of post-giardiasis metabolic consequences
Post-giardiasis effectsCountrySelected references
Lower cognitive functionIndia, Peru, Turkey[40,67,68,76,77]
Lower intellectual quotient
Lower social quotient
Lower weightBrazil, Columbia, Ecuadora, Guatemala, Iran, Israel, Mexico, Rwanda, Turkey, United States[37-39,63,64,66-68,72,77,78,124-129]
Lower height
Failure to ThriveColumbia, Ecuadora, United States[64,66,127]
Nutrient deficienciesIran, Mexico, Tanzania[38,69,78,81]
Table 3 Extra-intestinal and long-term consequences of giardiasis
Post-infectious consequencesSpeculated mechanisms involvedReferences
Ocular pathologiesSpeculated involvement of toxic metabolites produced by the parasite[47-49]
ArthritisBacterial antigens in synovial fluids possibly due to increased intestinal permeability[50-52]
AllergiesAlteration in antigen uptakeDysfunction of the intestinal barrier[54-57]
Hypokalemic myopathyLoss of potassium related to diarrhea, impaired nutrient and electrolyte absorption[59-62]
Failure to thriveInadequate food intake, Reduced nutrients absorption, excessive utilisation of energy, Steatorrhea, maldigestion, malabsorption[38,39,63-65,69,71,118]
StuntingNutritional status, sanitary, socio-economic conditions, loss of intestinal surface area, maldigestion, malabsorption[37,63,64,67,77,121]
Impaired cognitive functionsChronic malnutrition and stunting following G. duodenalis infectionNutrient malabsorption and micronutrient deficiencies[40,41,63,64,68,76-78]
Chronic fatigue syndromeAltered natural killer-cell levelsLower ratio CD4:CD8[15,82-87,89]
Post-infectious irritable bowel syndromeMicroscopic duodenal inflammationInteraction host - gastrointestinal microbiotaIncreased T-cells and Mast-cells[14,84,93,100-105]
CancerNo cause-to-effect established[113-116]