Baermann technique

Purpose

  • For separation of helminth larvae from cultured fecal material

Principle

The Baermann technique is based on the active migration or movement of larvae.
  • Feces are suspended in water.
  • The larvae move into the water.
  • They sink to the bottom and can be collected for identification.


Procedure

  • Take a funnel and fit a short piece of tubing to the stem.
  • Close the tubing with a clamp or spring clip.
  • Support the funnel on a single stand.
  • Double layer of cheesecloth
  • Add 5-10 grams of fecal material
  • Put this material the funnel in the suspended form (cloth should not touch the funnel)
  • Fill the funnel with lukewarm water.
  • Make sure the fecal material is covered.
  • Leave the apparatus to stand for 24 hours.

Larval recovery

  • Draw off a few mL of fluid from the stem of the funnel into a test tube.
  • Leave for sediment for at least 30 minutes.
  • or centrifuge at 1000 rpm for 2 minutes.
  • Take a small droplet of the sediment to a microscope slide.
  • Add a drop of iodine to fix the larvae and gently place a coverslip over the drop.
  • Free-living nematodes will stain dark brown very quickly
  • Parasitic spp. Light stain due to protective sheath










Pseudoparasites/Pitfalls
  • Wide variety of objects that resembles parasites/larvae are termed as Pseudo Parasites/Pitfalls
  • They leads to mis-identification
  • With experience, these can be covered
 What can be these?
  • Inorganic materials
  • Oil droplets
  • Yeasts
  • Fungi
  • Plant material
  • Plant grains, fibers, straws
  • Larval or adult insects
  • Cellular elements

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