is the cause of the bladder-worm, producing sheep-gid, or sturdy
(_Cœnurus cerebralis_). This tapeworm, which may live in the intestine
of other animals besides the dog, has a circlet of hooks, is from
fourteen to sixteen inches long, and consists of about two hundred
joints. It generally lives in the intestine of the sheep-dog, in
correspondence with which is the fact that the bladder-worm lives in the
brain of young sheep. If a sheep-dog harbours _Tænia cœnurus_ in its
stomach, a sheep may very easily take up a joint with grass or heath.
The joint is then digested in the sheep’s intestine, and the larva
escapes from the egg. It bores through the wall of the sheep’s
intestine, gets into the circulation, and is carried by the blood-stream
to various parts of the body; it can only develop further, however, in
the brain (or spinal cord). After the minute larvæ have reached the
cavity of the cranium they move about on the outer surface of the brain,
and dig out channels there till they find a suitable place for further
growth. The larva now becomes a bladder-worm, which gradually grows,
until it attains a size varying from that of a nut to that of a hen’s
egg. It develops numerous tapeworm heads, even from three to four
hundred. These become tapeworms if a sheep is killed by the parasite,
and its head devoured by a dog or fox.
The disease caused by the presence of bladder-worms in the brain is
called “gid,” or “sturdy,” also “staggers.” Two stages can be
distinguished in it. During the first period the symptoms of disease are
chiefly due to the wounds which the larvæ make on the surface of the
brain, and the consequent inflammation of the investing membranes. Even
in this stage the disease may be fatal, but the symptoms cease as soon
as the larvæ cease to move about. The bladder-worms are only able to do
harm by the pressure they exert, which is small at first, though it
gradually becomes greater. The first stage of gid manifests itself in
late summer, the second in late autumn, winter, or spring, according to
the rate at which the bladder-worms develop. The symptoms of the first
stage are caused by the increased flow of blood to the brain and head
generally, resulting from the irritation which the larvæ exert. (Head
very hot. Eyes bloodshot. The sheep are sluggish but restless, and carry
their heads in a strange way, to one side, bent back, or turned up. They
often run round in a large circle. There may also be gnashing of the
teeth, foaming at the mouth, squinting, convulsive movements, and loss
of consciousness.) The symptoms of the disease in its second stage are
the result of pressure on the brain and some of the arteries of the
brain and skull. (The sheep affected separate themselves from the
others, and generally hang their heads. Gaze fixed. Occasional loss of
consciousness. Movements strange; run or turn round in a circle. The
sheep often staggers and falls to the ground. The bones of the skull
become thinner at the place under which the bladder-worm is found,
sometimes even as thin as paper.)
_Remedies_: Trepanning, as the bladders lie just underneath the roof of
the skull. _Prevention_: Reducing the number of sheep-dogs; giving the
dogs medicine to rid them of tapeworms in spring and summer;
administering a specific to the yearling sheep in July and August,
suitable for driving out any tapeworm larvæ which may be present in
their intestines; _burning_ (instead of _burying_) the heads of sheep
affected with staggers which have died or been slaughtered. It is but
rarely that all the larvæ living on the surface of the brain die between
the first and second stages of the disease. A sheep affected by gid is
therefore almost sure to die, and should be slaughtered as soon as
possible. Compare “false gid,” p. 189.