Baermann technique: fecal larvae culture : Baermann technique: fecal larvae culture Dr.Kedar Karki Purpose : Purpose The Baermann technique is used to separate larvae from faecal material.
Diagnosing lungworm infection
The identification of third stage larvae [L3] from a faecal culture. Baermann technique: Principle : Baermann technique: Principle The Baermann technique is based on the active migration or movement of larvae.
Faeces are suspended in water.
The larvae move into the water.
They sink to the bottom and can be collected for identification. Baermann technique: Equipment : Baermann technique: Equipment There is no standard equipment for this technique.
Each laboratory adapts its own procedure.
Commonly used equipment is illustrated and a list is shown below. Equipment List : Equipment List Funnel – size according to need
Rubber or plastic tubing
Clamp or spring clip
Cheesecloth or dental napkin
Thin stick or metal rod
Test tube Pasteur pipette
Small petri dishes
Disposable paper towels
Spoon or spatula
Rubber band or length of string
Jug or flask
Microscope slides and coverslips
Iodine Equipment List : Equipment List Baermann technique: Procedure step 1 : Baermann technique: Procedure step 1 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. Baermann technique: Procedure step 2 : Baermann technique: Procedure step 2 Place a double layer of cheesecloth or dental napkin on a disposable paper towel or equivalent on the bench.
Using a spoon or spatula weigh or measure approximately 5-10 grams of faecal material.
Place the faecal material in the centre of the cheesecloth. Slide 12: Form a pouch containing the faecal material by holding the four corners of the cheesecloth together and moulding the cloth around the faecal material. Baermann technique: Procedure step 3 : Baermann technique: Procedure step 3 Using a rubber band or length of string close the cheesecloth pouch.
Push the stick or short metal rod under the rubber band or string so that the pouch can be suspended. Baermann technique: Procedure step 4 : Baermann technique: Procedure step 4 Place the pouch containing the faecal material in the funnel.
Trim off the excess cheesecloth.
Fill the funnel with lukewarm water.
Make sure the faecal material is covered.
Leave the apparatus to stand for 24 hours. Baermann technique: Procedure step 5 : Baermann technique: Procedure step 5 Draw off a few millilitres of fluid from the stem of the funnel into a test tube.
leave to sediment for at least 30 minutes. Baermann technique: Procedure step 6 : Baermann technique: Procedure step 6 Check sedimented sample in a petri dish for the presence of larvae.
This may be all that is required to diagnose the presence of nematode parasites but often more detailed examination is required.
This is because other parasitic or free-living nematode life-cycle stages may be present if the faecal sample was not fresh when processed or if it was collected from the ground. Baermann technique: Procedure step 7 : Baermann technique: Procedure step 7 Use a Pasteur pipette to transfer a small droplet of the sedimented fluid from the petri dish to a microscope slide.
Add drop of iodine to fix the larvae and gently place a coverslip over the drop.
Any free-living nematodes will stain dark brown very quickly while the larvae of parasitic species will only stain very slowly as the larval sheath protects the body. Baermann technique: Examination and interpretation : Baermann technique: Examination and interpretation Examine under compound microscope at 10 x 10 magnification.
Free-living nematodes stain deeply brown in iodine and can be distinguished by the presence of a double bulbed (rhabditiform) oesophagus. Ruminant L3: Trichostrongylus : Ruminant L3: Trichostrongylus Check sheath > Sheath present > Square head > Refractile bodies absent > Sheath tail short length: Trichostrongylus Head Tail Ruminant L3: Cooperia : Ruminant L3: Cooperia Check sheath > Sheath present > Square head > Refractile bodies present: Cooperia Cooperia
16 gut cellsHead square with refractile bodiesSheath tail medium tapering (Cooperia oncophora)or finely pointed and refractile (Cooperia curticei type)Length 666-956 µm Ruminant L3: Bovine Ostertagia : Ruminant L3: Bovine Ostertagia Check sheath > Sheath present > Square head > Refractile bodies absent > Sheath tail medium: Ostertagia Ostertagia ostertagi
16 gut cellsHead squareSheath tail forms medium coneLength 825-926 µm Ruminant L3: Haemonchus : Ruminant L3: Haemonchus Check sheath > Sheath present > Rounded head > Sheath tail medium length: Haemonchus Haemonchus
16 gut cellsHead narrow roundedSheath forms medium length tail ending in a fine pointLength 650-850 µm Ruminant L3: Nematodirus : Ruminant L3: Nematodirus Check sheath > Sheath present > Rounded head > Sheath tail long > Larval tail notched: Nematodirus Ruminant L3: Oesophagostomum/Chabertia : Ruminant L3: Oesophagostomum/Chabertia Check sheath > Sheath present > Rounded head > Sheath tail long > Larval tail not notched > 32 gut cells: Oesophagostomum/Chabertia Ruminant L3: Strongyloides : Ruminant L3: Strongyloides Check sheath > Sheath absent: Strongyloides Strongyloides
Oesophagus extends nearly half length of bodySheath absentLarval tail notchedLength 650-850 µm