The Phylum Platyhelminthes contains both the trematodes and
cestodes. The trematodes (flukes) have an incomplete digestive
tract (a mouth but no anus) and have no body cavity, the
organs being imbedded in the parenchyma of the body. There are
2 subclasses of parasitic flukes: the Monogenea, whose members
are parasitic only as adults and the Digenea, whose members
have two or more hosts in their life cycle, and the first host
is a mollusk.
The Cestodes (tapeworms) have no mouth, as adults they live
in the small intestine of their hosts and absorb nutrients
through their tegument (external surface). The tapeworm life
cycle involves an intermediate host. In many species the larval
stages cause more pathology than the adult worms.
The Phylum Acanthocephala contains parasites, which as
adults, lack a digestive tract and live in the small intestine
of their hosts. As the name suggests, they have a spine-covered
proboscis at their anterior end (they are also known as "thorny
headed worms"). Although many different species are found in
wildlife, only one species is a parasite of domestic livestock
Be able to identify the following trematode eggs:
- Any trematode egg (A brown egg with an operculum is considered a trematode egg or a trematode-like egg.)
- Fasciola hepatica (the operculum, the size and the host should be sufficient to identify this egg).
- Dicrocoelium dendriticum (the operculum, the size and the host should be sufficient to identify this egg).
- Paragonimus kellicotti (the operculum surrounded by a thick ring and the size should be sufficient to identify this egg).
Echinococcus spp. and Taenia spp. (Small (35 - 45 um) brown eggs with striated border).
Dipylidium caninum (expressed from a proglottid, they will be in packets).
Anoplocephalids - Anoplocephala spp.and Moniezia spp. (Triangular or square eggs).
Be able to identify the adults of the following:
8. Fasciola hepatica (by size, shape and location within the host).
9. Dicrocoelium dendriticum (by size, shape and location within the host).
10. Fascioloides magna (by size, shape and location within the host).
11. Paramphistomum spp. - (by size, shape and location within the host).
12. An acanthocephalan (a predilection site in the small intestine, and the presence of a anterior proboscis covered with spines coupled with the lack of suckers on the anterior end is enough to identify an adult acanthocephalan.)
13. Anoplocephala perfoliata (by the size, shape and predilection site)
Be able to identify the proglottids of:
14. Taenia spp. (When gently flattened they are square to rectangular.)
15. Dipylidium caninum (When gently flattened they pinch in at the ends - “cucumber seed” shaped.)