Laboratory diagnosis of Parasitic Infections

Name of the organism/Disease



Blood examination

Direct examination


Ascarisis lumbricoides

Stool or vomit.

Bile by duodenal intubation.

-Egg: direct microscopical examination of a saline emulsion of the stool.

-Concentration: flotation method

-Unfertilized eggs don’t float in salt solution.

-Solitary male harbouring: no egg.

-Egg in bile.

Eosinophilia during early stage of invasion. If present in the intestinal phase suggests associated strongyloidiasis and toxocariasis.

Finding of adult worms. Antihelminthic drug increase expulsion of worms.

X-ray with barium emulsion.

Allergic dermal rxn(scratch test) with powdered Ascaris antigen.


Freshly passed stool. Bile (duodenal intubation)

Demonstration of Giardia trophozoite (in diarrhoeic stool) and cyst.

Intestinal amoebiasis


Blood (blood shows moderate lecocytosis)

Cellular exudates: scanty, containing only nuclear mass (Pyknotic bodies) of only a few pus cells, macrophages and epithelial cells.

Clumped RBC:reddish yellow or yellow green in color

Charcot-Lyden crystals.
*not pathognomonic.

    *Suggests careful examination of stool.

     *Diamond shaped or whetstone shaped crystals, clear and refractile (5-50µm in size).

Demonstration of E.histolytica by examining trophozoites in acute cases, characteristic movement & presence of ingested RBC.

Moderate leucocytosis.

An offensive dark brown, semifluid stool, acid in rxn, admixed with blood, mucus and presence of much fecal matter.

Serology always negative. Although there is tissue invasion, it has not existed long enough to produce detectable antibody.

Amoebic live abscess

Pus by exploratory puncture.

Liver biopsy in miliary amoebic hepatic abscess.


Demonstration of trophic form of E. histolytica.

Present in less than 15% cases of amoebic liver abscess.

Leukocytosis (15,000-30,000 per mm3) of blood.

DC shows Neutrophil granulocytes to be 70-75%.

OTHERS: Intradermal test: erythema.

Radiological Examination: shows evidence of basal pleurisy.

Hepatic Photoscan.

Presence of specific antibodies circulating in the blood of infected individual.

CFT, precipitin test, immobilization test, Test of Goldman, IHA, Passive cutaneous anaphylaxis.

Pulmonary amoebiasis
Demonstration of trophozite of E. histolytica.
Expectorated pus when examine fresh, may demonstrate the motile form(trophozoite) of E.histolytica.

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