Giardia lamblia; Giardia intestinalis

Introduction

Etiologic agent of giardiasis.

Epidemiology

• both endemic & epidemic infections worldwide
• especially in travelers, campers, children & workers in day care centers & homosexual men
• infectious cysts live in the environment
• trophozyte attaches to the small intestine; responsible for symptoms in inected individuals
• infection generally occurs via drinking contaminated water
• Giardia is not killed by usual concentrations of chlorine in murine municipal water
• water supply must be filtered to eliminate Giardia
• campers must boil water from streams or lakes in endemic areas

Pathology

• etiologic agent of giardiasis
• trophozoites multiply in the small bowel & attach to the mucosa by a ventral concave sucking disc
• disruption of the brush border
• disaccharidase deficiency

Laboratory

• Giardia lamblia antigen
• Giardia lamblia serology
• Giardia lamblia DNA
• Giardia lamblia 18S rRNA
• light microscopy of stool specimen
  • trophozoites
    • are predominant in watery feces
    • direct mounts are helpful for demonstrating trophozoites
    • may be seen on permanently stained slides
    • pear-shaped with tapered posterior end
    • two nuclei that give the appearance of a smiling face with prominent eyes
    • sucking disc on ventral surface
    • 4 lateral, 2 ventral & 2 caudal flagella are generally not visualized on wet mounts or stained specimens
    • measure 12-15 by 9-10 um (range 10-20 um in length)
  • cysts
    • are more likely to be found in formed stools
    • may be seen in direct mounts or with concentration techniques
    • may be seen on permanently stained slides
    • oval & generally with 4 nuclei
    • dark-staining median bodies that cross longitudinal fibrils
    • cytoplasm often retracted from cyst wall
• Giardia lamblia stool culture
• also see giardiasis

More general terms

• Giardia

Additional terms

• giardiasis (beaver fever)