Giardia
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Recognition
- Flagellate protozoa
- Found in the intestine of humans
- Associated with chronic diarrhoea
- Foundin both wild and domestic animals
- 15-20μm long
- Pear-shaped
- 8 flagella
- Large adhesive discs to hold onto intestinal mucosa
Life Cycle
- Simple and direct
- Trophozoites attach to intestinal wall
- Reproduce by binary fission
- Form cysts of 10μm
- Cysts formed intermittently
- Immediately infective when passed in faeces
- Prepatent period of 5-6 days
Pathogenesis
- Commonest cause of protozoal diarrhoea of man in the UK
- Common in domesticated animals
- Infections often asymptomatic in domestic animals
- Can cause cillous atrophy leading to malabsorption
- Infection can persist for weeks to months if not treated
Epidemiology
- Infection via direct oral-faecal route or through contaminated water source (water-bourne)
- Wild animals may act as a source of infection for humans
- E.g. Beavers
- Divided into 7 species
- G. duodenalis most commonly infects humans
- Some subspecies are zoonotic
- G. duodenalis most commonly infects humans
Diagnosis
- Faecal examination
- Cysts need to be distinguished from pollen grains and yeasts
- Cysts excretion is intermittent
- Faeces need to be collected over a 3 day period
- Cysts are heavy
- Needs higher density floatation fluids
- Do not float well in saturated sodium chloride solution
- Immunoassays
- Detecting cyst antigen in faeces
Control and Treatment
- Sanitation and hygiene
- Minimise risk of human infection
- Boil (or sterilise through other means) drinking water in regions of the world where drinking water may be contmainated
- Avoid uncooked foodstuffs
- Contaminated by washing
- Treatments
- Metronidazole
- Flagyl, Torgyl
- Fenbendazole
- Panacur
- Metronidazole
- Vaccination
- Killed trophozoites
- Availbale in the USA for cats and dogs
- Decreases the excretion and viability of cysts
- Decreases environmental pressure