Larval emigration process

The larval emigration method , also known as the Baermann-Wetzel method or the funnel method , is a coproscopic detection method (fecal examination) for the detection of parasitic developmental stages ( larvae ) of live-bearing gastrointestinal parasites. After separate cultivation, it is also possible to detect larvae excreted in the egg.

Principle of the procedure

The larvae to be detected tend to migrate out of the faeces when there is sufficient moisture. They can move sideways, but not swim, which is why they sink into free liquid.

The procedure is suitable for the detection of:

• viviparous parasites ( e.g. lungworm larvae )
• Nematode larvae after previous cultivation

execution

A glass funnel is required for this process, at the end of which a hose that can be closed with a clamp is attached. This funnel is filled with water. A sieve with a gauze insert (a nylon stocking also works) is inserted. The fecal sample is placed in the sieve and the funnel is filled with water until there is contact with the fecal sample. The apparatus must now be left to stand for at least six hours (better overnight). After the waiting time, carefully open the clamp on the tube and allow the first drops to drip onto a microscope slide or into a Petri dish . The screening can now take place in the microscope .

A somewhat simplified procedure is possible for shaped feces from small ruminants. The feces are wrapped in gauze and placed in a Petri dish filled with water.

Cultivation for the detection of nematode larvae

In order to be able to detect nematode larvae, the fecal sample must be cultivated before the apparatus is loaded. For this purpose, the mixed fecal sample is placed on sterilized sawdust (sterilization by heating for two hours at 150 ° C). The mixture is moistened again and left in the incubator at 24-25 ° C for eight to ten days . The sample must be ventilated and moistened daily. After the time has elapsed, the sample can be subjected to the actual larval migration process.

See also

• Sedimentation process
• Flotation process

Web links

• Illustrated description of the procedure: Parasitological faecal examination - emigration or funnel procedure method according to Baermann-Wetzel. CVUA OWL - Chemisches und Veterinäruntersuchungsamt Ostwestfalen-Lippe, accessed on November 19, 2016 . 

literature

• Ronald Schmäschke: The coproscopic diagnosis of endoparasites in veterinary medicine . Vetpraxis Spezial, Verlag Ashgate Publishing, Ltd., 2013, ISBN 9783899936766 , p. 40.