Organism

Giardia lamblia
Flagellate protozoan – lives in duodenum or jejunum.
Incubation= 7days-3months

Transmission

Faecal-oral/ from pets or birds
(humans are main reservoir of infection)
Typically from drinking water contaminated with giardia cysts (killed by boiling but NOT chlorination)
 

Epidemiology

Prevalence approx. 20-30% in developing countries
Also significant numbers of cases seen in USA
 

Pathogenesis

Trophozoite parasite multiplies in upper bowel by binary fissionàlarge areas of mucosa may be colonized in heavy infection
àDisrupts brush-border and affects enzyme activity.
àStimulates inflammatory cytokine response àsecretion of fluid and electrolytes and cell damage.
Trophozoites encyst as then pass through the intestine and become infective.
 

Clinical features

Most infections are asymptomatic.

acute phase lasts 2 – 4 weeks.

symptoms are worse in immunodeficiency.
(Sometimes Explosive) watery diarrhea (NON-bloody)
mild abdominal pain
bloating and nausea
steatorrhoea
low grade fever
Chronic diarrhea with HIV
 

Complications

malabsorbtion
lactose intoloerance
dehydration
weight loss
chronic inflammation can lead to increased risk of cancer

Diagnosis

Stool antigen
Culture of blood/ urine/stool/bone marrow/duodenal aspirates
Microscopy of stool for cysts and trophozoites.
 

Treatment

Metronidazole or tinidazole

Prevention

Good personal hygiene
Access to clean water.

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