13.2 - genus giardia Flashcards
pathogenic giardia
giardia duodenalis
flagellated protozoan
giardia duodenalis is ingested through
contaminated food, water or by faecal oral contact
human infections with giardia are found in
populations in areas of poor sanitation and limited water treatment
40-60% prevalence in such populations
after infection
35% symptomatic
15% asymptomatic cyst shedder
50% no symptoms, infection cleared
acute infection presentation
diarhhoea - foul smelling and fatty flatulence abdominal cramps bloating malaise nausea sometimes vomiting weight loss
chronic infection
fatty, loose stools flatulence abdominal cramps bloating malaise profound weight loss malabsorption stunted growth in children
pathogenesis of giardiasis
absorptive/secretory surface area of small intestine is maximised by structure of villi and microvilli
trophozoites adhere to small intensity al epithelial cells and destroy villi/microvilli
structural and functional abnormalities caused by adherence of trophozoites to small intestinal epithelial cells
mild to severe villas atrophy
shortening of microvilli
disruption of epithelial junctions
apoptosis of epithelial cells
deficiencies in epithelial enzymes (disaccharidases)
increased glucose, sodium and chloride levels in lumen
migration of intestinal bacteria and antigens into submucosa
diarrhoea mechanisms of giardiasis
loss of intestinal mucosal surface area - less water reabsorption
leaking of water through disrupted epithelial junctions
carbohydrates not digested by disaccharides, not absorbable, Exert osmotic force to pull water into lumen
loss of chloride from cells draws water into lumen
damaged epithelium result in malabsorption of nutrients - if chronic causes weight loss and growth stunting
loose stools
even following successful eradication of parasite with drugs, loose stools may persist for weeks until epithelium repairs
