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Important Helminth Parasites of Poultry
pigeon, turkey, duck, fowl, pheasant and several other related wild birds.
Mainly the crop and oesophagus are involved and the stomach is seldom
affected. The worms usually live buried in the wall and may penetrate as
deep as the boundary of the muscularis. The eggs are voided with the faeces
and under favourable conditions, they develop to the infective stage in three
to four weeks' time. Though ordinarily a bird becomes infested with capil-
larids directly through contaminated feed or water, in certain cases earth-
worms are known to serve as facultative hosts, as in the case of the gape-
worm.
Mild infestations produce no marked symptoms. Fowls appear to possess
a certain degree of inherent immunity to the effects of these parasites. Chickens
up to four months of age are fairly susceptible to infection and the immunity
of the older birds may occasionally break down due to lowered resistance of
one kind or other. Avitaminosis in chickens may be responsible for heavy
infestations with these worms. Turkeys, ducks and pheasants are specially
susceptible to the harmful effects of the capillarids, in which severe tissue
damage and high mortality may be produced. The principal symptoms in
the affected birds are the refusal of grain, but acceptance of soft feed, unnatural
position of the head, arching or stretching of neck, droopiness, anaemia, emacia-
tion and lameness. The worms cause overloading of the crop resulting in
' indigestion ingluviale ', which in ducks may produce dyspnoea by pressing
on the vagus nerve. The walls of the affected parts of the digestive tract
may show catarrhal inflammation, thickening and loss of elasticity, enlarg-
ment of the lymph follicles, necrosis and sloughing of mucosa and the presence
of pseudo-membranes, composed of necrotic substances with fibrin and poly-
nuclear leucocytes.
Diagnosis is made by the finding of the typical lemon-shaped, double
operculated eggs in the faeces ; or in the scrapings of the necrotic membranes
on autopsy of a typical case. On account of their position in galleries within
the wall of the digestive tract of the bird, the removal of these worms with
medicinal treatment is difficult. However, carbon tetrachloride in doses of
1 c. c. a week or iodine capsules may be tried. Proper feeding and stringent
preventive measures alone can help in fighting the infestation. The birds
should be given soft and easily digestible feed and the young birds should be
isolated from the adult and infected ones.
The ' gapes ' in poultry is caused by a strongyle nematode—Syngamus
spp.—which is also known as the gape-worm, Y-worm and forked-worm.
In their immature stages the gape-worms inhabit the lungs and air sacs but
in the adult stage they occur in the trachea and bronchi of the host. They
are more or less cosmopolitan and have been reported from the turkey, fowl,
pheasant, goose, duck, pigeon, guinea-fowl, peafowl, partridge and various
other birds. As the name suggests, the adult males and females remain per-
manently joined in copula in the form of the letter Y, attached to the mucous
membrane of the upper part of the respiratory tract. The eggs are laid by
the gravid female while still in copula and pass out, under the margin of the