Page 153 - The Veterinary Laboratory and Field Manual 3rd Edition

122 Susan C. Cork and Mani Lejeune

2 Refill the tube with water and leave overnight Alternatively, the Baermann method can be
at room temperature (25°C) under light. used, this is essentially the same as the above
3 The next day remove the paper ‘bag’ con- method but the first three steps are performed
taining the faecal material from the tube and using the Baermann equipment. The last steps
discard it. (4–6) are the same (Figure 3.7).
4 Centrifuge the tube containing the larvae and A modified Baermann larval extraction tech-
water and discard the majority of the super- nique is now commonly used because it is simple
natant. and requires less space to perform. It is sensitive
5 Suspend the sediment in the small amount of and comparable to traditional Baermann tech-
fluid remaining in the tube and add 1 drop of nique. The method is summarized below.
Lugol’s iodine.
6 Using a Pasteur pipette transfer the suspen- 1 Make an 8 × 8 cm envelope of cheese cloth/
sion on to a microscope slide in 3-drop pools. kim wipes sandwiched between two window
Apply a cover slip to each ‘pool’ and examine screens.
under the microscope using the low-power 2 Place 2–5 g of faeces inside the envelope on
lens. Identify and count all the lungworm lar- the side of cheese cloth.
vae present. 3 Submerge the faecal envelope into 200 ml

Figure 3.7 The Baermann equipment (A) used for extracting lungworm and an illustration of a lungworm
larva (B). A sieve (250 µm) is placed in the wide neck of a glass funnel held in a retort stand. A rubber
tube is attached to the bottom of the funnel which has been partially filled with water. Gauze is placed in
the sieve and faeces are added. The apparatus is left overnight after filling the funnel with water. Larvae
migrate out of the faeces and are collected in the neck of the funnel to be released into the test tube below.
Next progress with steps 4–6 as outlined for larval extraction. See also Plate 6.

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