Lab Manual Appendix

Lab 1
Lab 2
Lab 3
Lab 4
Lab 5
Lab 6
Lab 7
Lab 8
Lab 9
Lab 10
Lab 11
Lab 12

Lab Demonstrations

Lab 1
Lab 2
Lab 3
Lab 4
Lab 5
Lab 6
Lab 7
Lab 8
Lab 9
Lab 10

Introduction

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.

Objectives Checklist

Be able to identify the following trematode eggs:

1. Any trematode egg  (A brown egg with an operculum is considered a trematode egg or a trematode-like egg.)
2. Fasciola hepatica   (the operculum, the size and the host should be sufficient to identify this egg).
3.  Dicrocoelium dendriticum  (the operculum, the size and the host should be sufficient to identify this egg).
4. Paragonimus kellicotti (the operculum surrounded by a thick ring and the size should be sufficient to identify this egg).

Be able to identify the adults of the following:

5. Fasciola hepatica   (by size, shape and location within the host).
6. Dicrocoelium dendriticum   (by size, shape and location within the host).
7. Fascioloides magna  (by size, shape and location within the host).
8. Paramphistomum spp. -  (by size, shape and location within the host).
9. 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.)

Lab Exercises

Phylum PLATYHELMINTHES

Class Trematoda

Subclass Monogenea

Fish: Gyrodactylus sp.
The adults of this monogenean are ectoparasites of fish.

Subclass Digenea

Large Animal Flukes

Sheep: Fasciola hepatica
These flukes live in the bile ducts.

Egg measures 140 X 80 µm and has an operculum at one end.

Fasciola hepatica Immature adults.	Fasciola hepatica Adults:  Note the size and the cone at the anterior end.

Fasciola hepatica miracidium This is the stage that hatches from the egg and invades the snail.  The cilia enable the miracidium to swim and the eyespots allow it to detect light and the direction of the light.	Limnea sp.   This snail is the intermediate host for Fasciola hepatica.

Fasciola hepatica Redia:   This stage will feed on snail tissue. Fasciola hepatica has 2 generations of redia, the germinal cells of the second generation will develop into cercariae.	Fasciola hepatica Cercaria:   This is the stage that leaves the snail and encysts on vegetation.	Fasciola hepatica Metacercaria:   This is the stage of Fasciola hepatica infective to sheep.

Click here to link to the Fasciola hepatica life cycle.

Deer: Fascioloides magna
A parasite of deer which causes an extensive amount of hepatic pathology in sheep, but little in cattle.

Fascioloides magna In deer the adult worms are encapsulated in the liver, but the capsule is connected to the bile duct to allow for the passage of eggs.  In cattle there is no opening to the bile duct and in sheep the worms wander through the parenchyma of the liver.

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Sheep: Dicrocoelium dendriticum
These small (1 cm) flukes are found in the bile ducts.

Dicrocoelium dendriticum Adults from the bile duct of a sheep.  Note the size and lack of a "cone" at the anterior end.  Compare to Fasciola hepatica.	Dicrocoelium dendriticum Adult: stained to show internal organs.	Dicrocoelium dendriticum Egg:   About 42 X 28 µm, with an operculum that is hard to see .

Sheep and cattle: Paramphistomum cervi
The small, conical fluke found in the rumen.

Paramphistomum sp. Adults:  From the rumen of a cow.  Note the "plump" nature of the body, they are not flat like the other flukes.

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Small Animal Flukes

Dogs and cats: Pragonimus kellicotti
Lung fluke usually found in fibrous cysts in the lung.

Paragonimus kellicotti Egg:   measures about 100 X 50 µm and has a collar or ridge around the operculum.	Paragonimus kellicotti Adult:   This specimen has been flattened and stained to show the internal organs.   These flukes are,  like Paramphistomum sp., round in cross section (see the next image).	Paragonimus kellicotti Adults are found in pairs in cysts in the lung parenchyma of the definitive host.  The second intermediate host is a crayfish.

Dogs and cats: Platynosomum fastosum
Adults measure 4 to 8 mm long and 1.5 to 2.5 mm wide and are found in the bile and pancreatic ducts of cats (and rarely dogs) in the Southeastern USA and the Caribbean. 

Dogs and racoons: Heterobilharzia americana

Schistosoma mansoni Adults (Male and Female). This relative of Heterobilharzia americana is a parasite of humans.	Schistosoma mansoni The schistosome eggs lack an operculum. The egg of Heterobilharzia americana does not have a spine like the one seen on this egg.

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