Laboratory 4
ASCARIDS, PINWORMS, AND TRICHOCEPHALIDS
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Checklist Material
| Ascaris suum
This is the ascarid of swine. Note its size and shape. The male is smaller than the female and has a curved tail with spicules. |
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| Parascaris equorum
This is the ascarid of horses. Note its size and the 3 large lips at the anterior end. (three lips are a characteristic of all ascarids.) |
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| Parascaris equorum
This slide shows the 3 lips (1 dorsal and 2 ventral). Focus up and down to see all three. |
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| Toxocara canis
The worms in this bottle were recovered from the 3 lb. puppy described in the case report. |
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| Toxocara canis and Toxascaris leonina
Adult worms. T. canis is much larger, the males measure up to 10 cm and the females up to 18 cm long T. leonina males are up to 7 cm and the females are up to 10 cm. Recall the biological differences between the two species: Host(s), transmission options, larval migration (or not) and the resulting differences in pathogenesis. Are both equally significant in public health? |
Toxascaris leonina |
Toxocara canis |
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| Toxocara cati
These are the adults of the common ascarid of cats. Note that the cervical alae can be seen with the naked eye. |
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| Toxocara cati
Note that the cervical alae of this ascarid terminate abruptly, unlike those of T. leonina the other ascarid of cats. Thus, ascarids that are expelled in the feces of cats can be easily distinguished. |
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| Oxyuris equi
These are adults of the pinworm of horses. Formerly a very common parasite of the large intestine, its susceptibility to modern anthelmintics has all but eliminated this nematode from horses in this part of the country. Note the females have long thin tails (a characteristic of the family) while the males have a blunt tail with caudal alae and a single spicule. |
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Other related Nematodes
| Baylisascaris procyonis
Adults from the small intestine of a raccoon. This worm lacks cervical alae. As has been pointed out in the lecture, this is an increasingly important parasite in veterinary public health. Although its larvae are not as prevalent in humans as those of T. canis, they are large and highly neurotropic, causing this species to be especially pathogenic. The larvae (not adults) occur in humans (and other mammals and birds) where they are one of several causative agents of "larval migrans". |
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| Ascaridia galli
Adult worms. This parasite occurs in the small intestine of chickens, turkeys, geese, and many wild birds (e.g. crows). Males 50 - 76 mm Females 72 - 116 mm |
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| Heterakis gallinarum
These are adults. This is the most common caecal worm of ground-reared poultry. Note its size. The females are larger than the males. |
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| Trichuris vulpis
These are adult dog whipworms. Note the size and the long, thin anterior end (the "lash") and the short, thick posterior end (the "whip-handle") of the worm. Hence, the common name: "whipworm". |
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| Trichuris vulpis This museum specimen demonstrates an infection with the whipworm of dogs. Note that the thin anterior end is embedded in the mucosa, whereas the thick posterior end protrudes into the lumen. |
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| Dioctophyma renale
This nematode is one of the largest known and is found in the kidney of dogs and wild carnivores (especially fish eating carnivores, e.g. mink). It causes destruction of the kidney tissue until only a fibrous shell is left. Fortunately, only one kidney is usually parasitized. Note the very large size and its location (within the kidney). |
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To the left: anterior end
To the right: tail of male
