GIARDIASIS

GIARDIASIS

• In the world 1.5% to 20% of humans are affected with giardiasis caused by Giardia lamblia

• Age – More common in children under the age of 5 years followed by persons with age 31 to 40 years

• Sex distribution – equal in both sexes

• Mode of spread –

  •  Through contact with contaminated water which may either through

    • Contaminated tap water

    • Recreational exposure in lakes, rivers and swimming pools

  • Person – to – person spread in

    • day care centres

    • homosexuals

  • Through contaminated food

• Etiopathogenesis

  • Giardia exists in two forms

    • Trophozoite –

      • Motile form which is pear shaped measuring 12μm to 15μm in length and 5μm to 9μm in width

      • A pair of nuclei is located in anterior half of the organism, with basal bodies lying between the anterior poles of the nuclei

      • 4 pairs of flagellae originate from the basal bodies. one pair on the ventral surface and 3 pairs on periphery

    • Cyst –

      • An elliptical infective form measures 6μm to 12μm X 6μm to 10μm

      • It contains 2 to 4 nuclei and the flagellae are retracted into axonemes

      • A median body and curved fibrils may also be present

  • Cysts remain viable in cold or tepid water for several months

  • Cysts are ingested and excystation begins in stomach

  • Trophozoites came out in the duodenum and upper jejunum and they colonize in the intetsine

  • Bile salts stimulate excystation, growth and replication

  • They penetrate the mucus gel layer and attach to the epithelial microvilli via their ventral suction disc

  • Attachment of microorganism to the brush border leads to alteration resulting in malabsorption

  • Villous blunting and shortening may occur

  • Epithelial damage due to toxin produced by microorganism may occur

  • Diarrhea occurring in giardiasis may be due to bacterial overgrowth, bile salt deconjugation and bile salt uptake by the organism

• Clinical presentation

  • May be asymptomatic or may produce

    • Diarrhea

    • Malabsorption

    • Weight loss

    • Failure to thrive in children

  • Chronic diarrhea may lead to rectal prolapse

  • Chronic infection may sometimes be associated with reactive arthritis or synovitis

• Microscopic findings

  • In H&E stained sections – Giardia organisms appear pear shaped, about the size of an epithelial cell nucleus, with two nuclei

  • Organisms are gray or faintly basophilic

  • They have an eliptical shape with one nucleus visible in section

  • Rarely the organism can be demonstrated in the biopsy as the distribution in patch

  • 3 mucosal patterns seen in HPE of mucosa affected by Giardia are

    • No alteration

    • Normal villous architecture with increased intraepithelial lymphocytes and increased plasma cells in Lamina propria

    •  Partial or complete villous atrophy and crypt hyperplasia associated with variable degrees of inflammation showing increased intraepithelial lymphocytes and plasma cells in lamina propria

• Investigation

  • Stool examination – cysts can be demonstrated in stools

  • Detection of Giardia antigens in stool

  • PCR assay for detecting Giardia in stool

• Treatment and prognosis

  • Metronidazole/ Tinidazole/ Ornidazole/ Albendazole are used for treatment