[Illustration: FIG. 72.--Tapeworms.]

_The treatment is preventive_. Drainage water from a pasture infested with
snails harboring immature flukes is a source of infection, and should not
be used as a water supply for cattle and sheep. In sections where the
disease is prevalent, sheep should not be pastured on low, poorly-drained
land. Such land should be used for pasturing horses and cattle, but if
possible, it should be first drained and cultivated. Careful feeding and
good care may help the affected animals to recover.

[Illustration: FIG. 73.--Tapeworm larvae in the peritoneum (_Cysticercus
cellulosa_).]

TAPEWORMS OR CESTOIDES.--Tapeworms are formed by a chain of segments,
joined together at their ends, and are flat or ribbon-shaped (Fig. 71). The
head segment is small, and possesses either hooks or suckers. It is by
these that the worm attaches itself to the lining membrane of the
intestine. The anterior segments are smaller and less mature than the
posterior segments. Each segment is sexually complete, possessing both the
male and female organs, and when mature, one or more of them break off and
are passed out with the faeces. The mature or ripe segments are filled with
ova. On reaching the digestive tract of a proper host, usually with the
drinking water or fodder, the embryo is freed from the egg. The _armed
embryo_ uses its hooklets in boring its way through the wall of the
intestine. It then wanders through the tissues of its host until it finally
reaches a suitable place for development (Figs. 71 and 73). On coming to
rest, it develops into the larva or bladder-worm, which when eaten by a
proper host gives rise to the mature tapeworm.

The following tables give the most important tapeworms: