Agriculture Reference
In-Depth Information
Eggs are passed in the faeces of pigs and are very
resistant to temperature extremes. The egg is viable for
more than 4 years in the environment. After ingestion,
the egg hatches in the small intestine, and the larva pen-
etrates the intestinal mucosa and travels to the liver and
then via the circulation to the lungs and onto the small
intestine via the bronchi, trachea and pharynx.
An effect of the migrating larvae on the lungs is 'milk
spot' or 'white spot' which appears as cloudy whitish
spots of up to 1.0 cm in diameter on the surface of the
liver and results from a fibrous repair of inflammation
reactions to the passage of larvae in the livers of previ-
ously sensitised pigs.
Echinococcus granulosus
: Hydatidosis
and hydatid cyst
This is a small tapeworm of the dog with intermediate
hosts which include domestic and wild ruminants, man
and primates, pigs and lagomorphs. Eggs are passed in the
faeces of the dog. After ingestion by the intermediate host,
for example, sheep, the ova hatch and the oncospheres
penetrate the gut wall and travel to the liver (70%) or lungs
(25%) and occasionally to other organs and tissues (5%).
Transmission to humans is not via consumption of infested
bovine organs but rather through the handling of infected
dogs or contaminated soil, water or food (Fig. 9.21).
1a
4
A
B
1b
3
a
b
2
E. multilocularis
B 2 c
II
III
Figure 9.21
Life cycle of Echinococcus multilocularis (Courtesy of Pro A.T. Trees).
