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• Flagellate protozoa

Disease

• Giardiasis

• Infection of upper small bowel
• Attaches to intestinal mucosa
• ? causes malabsorption of fat
• Worldwide distribution
• Humans are main reservoirs
• Occasional animal carriers e.g. beavers
• Cysts passed in stool
• May be large numbers of asymptomatic cyst excreters in population
• Cysts enter water supply

Features

• Pale bulky stools & flatulence
• abdominal pain
• No blood
• Anorexia
• Weight loss

Course

• Faecal-oral spread
• Incubation 14 or more days
• Sub-acute onset
• Prolonged course – may last weeks

Diagnosis

• Stool microscopy after formol-ether concentration
• String test / duodenal aspirate for trophozoites
  • Sample needs to be warm as tropohozoites encyst on cooling

Treatment

• Metronidazole

Prevention

• Chlorination
• Boiling