ORGANISM IDENTIFICATION: Helminths

Tips and Pitfalls!

1. The identification of helminth eggs is usually accomplished by examination of the wet mount (concentration wet mount); egg morphology on the permanent stained smear is often distorted, shrunk, and difficult to identify.
2. If the fecal smear is too thick or the stain (D'Antoni's or Lugol's iodine) too dark, helminth eggs will appear to be debris and may be missed.
3. Operculated eggs will not float using the flotation concentration method; the sediment will have to be examined, as well. If the flotation concentration is routinely used as the only fecal concentration method, both the surface film and the sediment will need to be examined prior to reporting the results. When operculated eggs come in contact with the high specific gravity of zinc sulfate (flotation solution), the operculum pops open, the egg fills with fluid, and sinks to the bottom of the tube.