Page 159 - The Veterinary Laboratory and Field Manual 3rd Edition

128 Susan C. Cork and Mani Lejeune

pigs, wild boar, wild carnivores, including bears, The appearance of the larvae is illustrated in
rodents, walrus and other marine mammals. It Figure 3.12.
can cause disease in humans who ingest under- 2 Pepsin digest
cooked infected meat or who accidentally ingest
cyst material while handling meat products. 1 Trim the fat and fascia from the muscle
The disease in humans may be serious and so sample and weigh out 25 g.
it is advisable to wear gloves when handling 2 Homogenize for 1 min in 250 ml of diges-
potentially infected samples. Samples to col- tion solution (1% HCl and 1% pepsin).
lect: 35–50 g of muscle especially the masseter 3 Incubate the homogenate overnight at
(cheek), tongue, intercostal muscles and the 37–40°C (or 4–6 h with stirring). Allow
diaphragm. to settle and decant about 200 ml of the
Tests: supernatant.
4 Centrifuge the sediment at 200×g for
1 Trichinoscopy 3–5 min and remove the supernatant.
Re-suspend the sediment in 30–50 ml of
This technique involves taking small sections saline.
of tissue and making a squash preparation 5 Take successive aliquots and place in a
by squeezing the tissue between two slides. Petri dish. Count the number of larvae
The slide is then examined under 10× mag- present under the microscope (stereo-
nification using a stereoscopic microscope. scope 12.5× magnification).

Figure 3.12 Squash smear to show the appearance of a Trichinella spiralis larva developing in the muscle
tissue of a pig (20×). Note that smoking and curing pork does not kill the Trichinella larvae.

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