Medical Parasitology Examination of faecesfor parasites
STOOL EXAMINATIONConcentration techniques • Increase relative number of parasites for scanty infections. • Reduce background fecal debris. Floatation Sedimentation • Non Operculated eggs • Trematodes ( Schistosoma.) • Cestode • Nematode (Hookworms) • Cysts • Heavy eggs (Ascaris egg) • Operculated eggs (Trematodes) • Larvae (Strong stercolaris.) • Cysts
1. Saline sedimentation • Emulsify part of the faeces in distilled water or saline. • Strain through gauze. • Allow to sediment. • Decant the supernatant fluid. • Repeat washing and sedimentation until the supernatant becomes clear. • Microscopically examine the sediment for parasites.
Saline sedimentation Mesh wire gauze Saline Emulsify Conicalflask stool Sediment
2. Formol Ether sedimentation • Add 10 ml of 10% formalin to the previous sediment. • Mix and allow to stand for 10 minutes. • Add 3 ml of ether. • Centrifuge. • Four layers will form: • Ether at the top. • Plug of debris. • Formalin. • Sediment. • Decant the supernatant and microscopically examine the sediment.
FormolEther Sedimentation Ether Ether debris 10% Formalin formalin stool Sediment Thorough mixing Conical flask centrif. tube • Ether adsorbs fecal debris & floats. • Formalin fixes & preserves the specimen.
1. Saturated NaCl floatation • Part of faeces is emulsified in saturated salt solution. • Strained in Erlenmyer flask. • The flask is completed to its top with salt solution without overflowing. • The flask is covered with a slide so as to contact the surface of the solution. • After 20 minutes the slide is turned over, covered and microscopically examined.
2. Zinc sulphate floatation • Part of stool is washed and sedimented by centrifuge. • The supernatant fluid is decanted and replaced by 33% ZnSO4. • Centrifuge. • The top fluid is microscopically examined.
Decant the supernatant Centrifuge Add ZnSO4