Sedimentation process

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The sedimentation method is a coproscopic detection method (fecal examination) for the detection of parasitic stages of development.

Principle of the procedure

The eggs to be detected are large, heavy eggs (polylecithale, i.e. containing a lot of yolk substance). Accordingly, these are quickly deposited in the sediment of the suspension. The procedure is suitable for the detection of:

The method only records about 30% of the eggs in the feces, so that the diagnostic reliability for the large liver fluke is about 68%. For other flukes such as the little liver fluke or Opisthorchiidae , the procedure is very unsafe.

Qualitative sedimentation method according to Benedek

First, a suspension is made from the fecal sample and tap water . A little detergent (a drop of washing-up liquid) may be added. The suspension is then poured through a sieve with a mesh size of 250-300 μm into a tall, narrow beaker . The sieve residue is rinsed with tap water until the beaker is filled and then left to stand for three minutes. Then the supernatant (part of the suspension above the sedimented area) is poured off and the glass is filled up again with tap water. This process is repeated once or twice depending on the degree of soiling. The supernatant is now poured off one last time. Two to three drops of methylene blue can be added to the sediment recovered last , in order to stain remaining parts of the plant (plant fibers from the faeces of herbivores). This background contrast staining is useful in order to be able to more easily distinguish the eggs and larvae from the remaining plant fibers. The sediment can now be examined under the microscope in a Petri dish . In the case of faecal samples from ruminants, the magnification may be sufficient, in the case of samples from carnivores a larger magnification is necessary because the eggs are relatively small here.

See also

literature

  • Thomas Schnieder: Veterinary Parasitology . Georg Thieme, Stuttgart 2006, ISBN 978-3-8304-4135-9 , p. 91 .