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| Endoparasites - Diagnosis |
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The veterinarian diagnoses most worm infections by identifying the characteristic eggs of the different species in the faeces. However, there are several exceptions. Filaroides osleri (not prevalent in New Zealand) are found in the sputum, while the eggs of the Capillaria plica are passed in the urine. Dipetalonema and Dirofilaria (not prevalent in New Zealand) microfilariae are found in the blood.
The major types of eggs which are present in canine faeces include: Strongyle-type eggs The hookworms, Ancylostoma, and Uncinaria, lay "strongyle type" eggs which 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 (fig 1). Lungworm and Whipworm Capillaria, the lungworm, and Trichuris vulpis, the whipworm, lay barrel shaped eggs with a transparent plug at each end. The plugs of the Capillaria egg are often asymmetrically placed (fig 2a lungworm, fig 2b whipworm). Toxascaris Toxascaris leonina eggs are slightly oval with smooth, thick shells (fig 4). Toxocara Toxocara canis, the common canine roundworm, lays round eggs with thick, pitted shells (fig 5). Cestodes Common Tapeworms Dipylidium caninum, known as the common tapeworm, sheds elongated segments called proglottids that resemble rice grains. Each proglottid contains packets of eggs (fig 6). Hydatid Tapeworm (not prevalent in New Zealand) and Taenia Echinococcus granulosus (not prevalent in New Zealand) and Taenia species are passed in the faeces as eggs that are round with thick striated coats. Each egg contains a larvae with six hooks. If ingested by human beings, Echinnoccus can cause serious damage. Therefore, faeces must be handled with caution (fig 7).
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