H. D. SRIVASTAVA                               397

occasionally produce inflammatory processes in the intestinal wall. No
satisfactory treatment is known. Avoidance of infected waters and the des-
truction of snails may help to control the infestation.

                         THE CESTODES OR TAPEWORMS

A large variety of tapeworms commonly infest poultry. They all occur
in the intestine and vary in size from a few millimeters to about a foot in
length. The eggs, either separately or contained in mature segments, are
passed out with the droppings ; but the development of the larval stage de-
pends on the eggs being taken up by some suitable intermediate host, in the
body of which they develop. A variety of invertebrates, such as slugs, snails.,
earth-worms, insects and crustacea, etc., serve as intermediate hosts of the
tapeworms infesting poultry. When an intermediate host is swallowed by a
suitable bird, the contained larval tapeworm is set free in the intestine. It
attaches itself to the wall of the gut and rapidly develops into an adult tape-
worm (Plate XXXIII, fig 2).

As adults, tapeworms live in the intestinal tract of the final host, and
through their body absorb nutrients taken in by the bird. However, in light
infestation, they do not have any marked detrimental effect on the health
of the bird. Turkeys and geese are most susceptible to the harmful effects of
cestode infestations, but fowls are less so. Ducks are rarely affected and
may harbour large numbers of worms without suffering much harm. Though
the different species of tapeworms of poultry vary greatly in their pathogeni-
city, in heavy infestations they all rob the host of much of its food. The
birds become unthrifty and show an unkempt appearance of the feathers,
droopiness, thirst, emaciation and anaemia. At first, appetite may remain
good but it gradually diminishes. The irritation caused by these worms
produces derangement of digestion and catarrhal condition of the bowels. In
laying birds, egg-production may be decreased or even suspended. The birds
suffer, from extensive muco-catarrhal enteritis, manifested by diarrhoea, the
excrement being usually streaked with blood. Convulsions or partial paraly-
sis, the leg being specially involved, may also develop. Young birds suffer
most and their growth is considerably retarded. The dwarf tapeworm-—
Davainea proglottina—penetrates deep into the mucosa, producing marked
enteritis, which is frequently hæmorrhagic in heavy infestations, while the
young forms of Raillietina echinobothrida and R. tetragona cause the formation
of nodules resembling those of tuberculosis. The wall of the intestine is
markedly thickened. The nodules may be visible from the peritoneal surface
and contain necrotic tissue and leucocytes. In light infestations, the bird is
rendered susceptible to other diseases like roup, while more severe infestations
frequently cause death.

Though the above symptoms and the presence of a large number of
proglottids or eggs in the faeces will reveal tapeworm infestations, specific
diagnosis should be made by finding the worms at autopsy. If there