Page 152 - The Veterinary Laboratory and Field Manual 3rd Edition

Parasitology 121

suspension (2–3 drops each) on a slide and
cover with a cover slip.
3 Examine under low power and count all the
eggs or larvae seen.
4 For identification of some eggs it will be
necessary to use high power.

Calculation: eggs per gram of faeces = no. eggs
counted × 15/nv

where n = no. of drops counted, for exam-
ple, 5 and v = volume of each drop, for
example, 0.03 ml (30 µl)

Therefore if 10 strongyle eggs were counted
under low power:

EPG = 10 × 15/ 5 × 0.03 = 10 × 100 =
1000

The appearance of helminth eggs commonly seen
in the faeces of domestic animals is illustrated
below in Figures 3.15 to 3.19 and in colour in
Plates 2a, 2b and 3. Figure 3.6 Flotation: (A) weighing 4 g of faecal
material; (B) dilution of faecal material in water and
filtering through a gauze pad into centrifuge tube;
culture, recovery and identification (C) filling of centrifuge tubes to equal level; (D)
of larvae diluting faecal pellet in Sheath solution after centrif-
ugation; (E) filling tubes enough to form meniscus,
Larval extraction for lungworm larvae cover tubes with cover slips; (F) remove cover slip
from tube and transfer to labelled microscope slide.
Unlike many helminths of veterinary impor-
tance, lungworm eggs tend to hatch before they See also Plate 5. Photo: Dr Regula Waeckerlin,
are coughed up and swallowed to be passed out University of Calgary, Canada.
in faecal material (see Figure 3.25). This means
that even when the faecal sample is fresh, lung- for detection of cattle lungworm (Dictyocaulus
worm eggs may not be present. The following viviparus) half saturated salt solution should be
method can be used to harvest lungworm lar- used instead of water.
vae from a sample to allow assessment of the
number present. Preferably, fresh faeces should 1 Weigh about 1 g of faeces and place the sam-
be used for this technique to avoid confusion ple in a small piece of tissue paper to form a
between lungworm larvae and the larvae of other small cylindrical ‘bag’. Fill a conical centri-
parasites and free-living nematodes. The follow- fuge tube with water and place the paper ‘bag’
ing technique is sensitive for the diagnosis of containing the sample inside. Try to avoid
lungworm infections in sheep and donkeys but trapping air beneath the bag.

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