Page 190 - The Veterinary Laboratory and Field Manual 3rd Edition

Parasitology 159

2 Practice land reclamation (drainage) and ulceration. In heavy duodenal infections, the
fencing around infected areas. most obvious sign is diarrhoea accompanied by
3 Chemicals such as copper sulphate have been anorexia and thirst. The adult parasites in the
used to kill the snail but they have the poten- fore-stomach rarely have a harmful effect even
tial to kill other aquatic organisms and to when many thousands are present and feeding
damage the environment, so widespread use on the wall of rumen or reticulum. Diagnosis
is not advised. is usually based on clinical signs with disease
more common in the young animals of the herd
B. Reducing land contamination and the use of especially those with a history of grazing areas
anthelmintics around snail habitats. As with Fasciola sp. clinical
The prophylactic use of fluke anthelmintics disease often occurs during the prepatent period
should be aimed at reducing pasture contami- so faecal examination for eggs may be of lim-
nation by fluke eggs. Note that not all drugs ited use. The paramphistome eggs are colourless
routinely used for nematode control are effective and can be easily distinguished from the yellow
against liver fluke. Fasciola sp. eggs which are similar in shape.
Control and preventive measures are similar to
1 Remove the fluke population in the host those for fasciolosis.
before the development of heavy infection.
2 Avoid grazing animals in areas previously Dicrocoeliosis
contaminated. (dicrocoelium dendriticum)
3 Always check the faeces of recently purchased
livestock for fluke infection before introduc- Dicrocoelium dendriticum is distributed worldwide.
ing them to new land. This parasite lives in the bile ducts of many her-
bivores, particularly sheep, cattle, goats, rabbits
and wild ruminants, such as deer. In heavy infec-
Paramphistomosis Stomach
fluke or conical fluke infection tions, production losses may occur as a result
(Paramphistomomum sp.) of chronic damage to the liver. The life cycle is
fairly complex and involves three hosts. These
There are several species of ruminal (stomach) eggs, when excreted through the faeces of the
or conical fluke of which Paramphistomum cervi definitive host contain fully developed embryos.
and P. microbothrium are the most common. They They hatch when ingested by the first interme-
are distributed worldwide but are more com- diate host (many types of land snail) in which
mon in sub-tropical and warm areas. The adult they develop into cercaria. These are passed in a
flukes are found in the rumen and reticulum of mass cemented together by slime (slime balls).
cattle, sheep and goats, and immature stages These are then ingested by ants (Formica sp.) in
are found in the duodenum. The life cycle of which they develop into metacercaria. Infected
Paramphistomes is similar to that of F. hepatica ants exhibit a peculiar behaviour of climbing up
and involves several species of fresh water snail, the grass blades during cooler parts of the day
which serve as the intermediate host. The patho- when animals are generally expected to graze.
genic effect in the final host (ruminant) occurs The final host becomes infected when these ants
during the intestinal phase of infection. The are ingested along with grass. In the final host,
young flukes feed on intestinal epithelium and the metacercaria hatch in the small intestine
cause severe erosions in the duodenal mucosa and the young flukes migrate to the main bile
characterized by oedema, haemorrhage and ducts in the liver. There is no migration in the

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