Gut protozoa Flashcards
E histolytica/dispar - lifecycle
Ingestion of mature cysts
Colonisation and excystation in large intestine
Trophozoite colonise surface of mucosa [do not penetrate] - multiplication and cyst formation
Passage of cyst in faeces
E histolytica/dispar - presentation
Most asymptomatic
Small proportion develop invasive intestinal amoebiasis - abdominal pain and bloody diarrhea
E histolytica/dispar - ulcer histology
Classical flask-shaped ulcer - narrow neck and wide at base
Hepatic amoebiasis - epidemiology
Males > females and children
-x7 risk in men
Hepatic amoebiasis - diagnosis
Many do not report GI symptoms prior
Positive serology - tends to be strongly positive
Imaging - CT, US
PCR
E histolytica/dispar - criteria for cysts
Round
10-15um
Up to 4 ring and dot nucleus
Blunt ended chromidial or chromatoid bars may be visible in minority of cysts [not visible with iodine stain - visible with iron haematoxylin stain]
E histolytica/dispar - treatment
Metronidazole
Should be followed by luminal amoebicide - paromomycin
E histolytica/dispar - diagnosis
Wet-folm microscopy - fixed and stained faecal samples
Serology - useful in non-endemic regions
PCR
Antigen detection tests
Giardia intestinalis - lifecycle
Contamination of water, food or hands/fomites with infective cysts
Colonise small intestine - trophozoite replicate
No invasion of tissues as part of life cycle
Giardia intestinalis - epidemiology
Young children > adults
= Children also shed larger number of cysts
Person to person transmission
Easily acquired:
-infectious dose very small [10 cysts]
-cysts are resistant to chlorine
-Cysts remain viable for weeks
Giardia intestinalis - symptoms
Diarrhea
Malaise, flatulence
Foul smelling faeces
Weight loss
Extra-intestinal symptoms = eyes, skins, joints, urinary tract
Giardia intestinalis - pathogenesis
Malabsorption of glucose, water and sodium
-Diffuse microvillus shortening
-Loss of epithelial barrier function - increased intestinal permeability
Giardia intestinalis - diagnosis
Wet film microscopy
Direct fluorescence antibody staining of cysts
Antigen detection - ELISA
PCR
Giardia intestinalis - identifying cysts
Oval
8-12um
4 nuclei at one end
Line [axoneme] running length of cyst and/or one or more curved median bodies
Giardia intestinalis - treatment
Metronidazole
Tinidiazole - may be more effective than metronidazole
Nitazoxanide
Paromomycin [safe in pregnancy]
