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| Endoparasites - Diagnosis |
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Diagnosis The veterinarian diagnoses most worm infections by identifying the characteristic eggs of the different species in swine faeces. Several exceptions exist to this general rule. Pigs are the intermediate hosts of Trichinella and of the tapeworm Taenia solium. The encysted Trichinella worm larvae and the larval cysticercus form of Taenia solium can be found in the muscles of the infected pigs at slaughter. Stephanurus, the kidney worm, lays eggs that pass out in the urine. The major types of eggs present in swine faces include: Nematodes Ascaris The egg of this nematode is oval and yellowish brown, with a very lumpy, thick wall (fig 1) Strongyloides This species lays embryonated eggs - that is, eggs containing developed larvae. The shell of the threadworm egg is oval, smooth and thin walled (fig 2) Metastrongylus The lungworm contains a larvae, is oval in shape and has a thin, roughened wall. Sometimes their eggs hatch while still in the host's intestine. In this case, larvae will be present in the faeces (fig 3). Strongyle-type egg "Strongyle-type" eggs are laid by Hyostongylus, Oesphagostomum and Trichostrongylus. These eggs are oval, with smooth thin shells. When laid, the eggs have already begun to develop and are called "segmented" because the inner mass has split into a group of cells. Species determination can be made by identifying adult worms at necropsy or by culturing the eggs found in the faeces until the distinctive larvae hatch. Trichuris Whipworm eggs are brown and barrel shaped, with a clear plug at each end (fig 5). Acanthocephalans Macracanthorynchus The distinctive egg of the thorny headed worm has a four-layered thick coat and contains a larvae. The outer coat is smooth, while the second layer is dark brown (fig 6).
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