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Important Helminth Parasites of Horses
In order to prevent foals and young horses from becoming heavily in-
fested before they have developed the necessary ability to cope successfully
with a heavy worm infestation, it is essential to pay special attention to the
sanitation of the foaling barns and paddocks and pastures. The paddocks and
pastures should be clean and free from infestation. Rotation of pastures
by moving horses to pastures meant for cows and sheep and vice versa, may
be useful, for the parasites of ruminants are not as a rule transmissible to
horses. Though the infestation is usually acquired on pastures, ill-kept
stables contribute in no small measure to it. Under pasture conditions the
eggs and larvae are exposed to many unfavourable influences, but in ill-kept
and manure-laden stalls they are not only protected from the adverse in¬
influences which prevail in the open but have an abundant supply of moisture,
shade and suitable temperature for their development. It is, therefore,
necessary to pay special attention to stable sanitation. Feed and water
should be supplied in such a way that contamination is not possible. Proper
disposal of manure as recommended in connection with the control of
strongyles will be of material help in this direction.
PIN-WORMS
The pin-worms—Oxyuris equi—are relatively long, whitish worms with
a fairly long and pointed tail. The males and females of this species inhabit
the caecum and large colon, but after fertilisation the mature females migrate
to the rectum. Unlike most worms, which lay eggs continuously while
living inside the host, the females of this parasite retains the eggs in the body
until she is gravid. The gravid female at intervals crawls out through the
anal opening to deposit her eggs in clusters on the skin of the peri-anal region.
The eggs develop outside the body of the host and in a few days the infective
stage is reached, when each egg normally contains a small worm inside the
shell. Ordinarily the eggs hatch only on being ingested by the host with
feed or water.
Though the fourth stage larva is known to feed on the intestinal mucosa
of the host, the adult worms are not found attached and probably feed on
the intestinal contents. The chief feature of pin-worm infestation in equines
is the irritation of the anus which may be produced by the passage of the
worms out of the anus, by the crushing of the females as they pass out or
by some irritant property of the eggs which are covered with a very sticky
fluid. The irritation caused may be so intense as to produce restlessness,
improper feeding, resulting in loss of condition and dull coat. The irritation
may cause the animal to rub its tail against the wall or post of its stall thus
causing loss of hair of the skin at the root of the tail and around it.
The above symptoms should lead to the examination of the peri-anal
region, where cream-coloured masses of eggs will be found. These may
be removed for diagnosis under a microscope. After starving for 36
hours, oil of chenopodium at the rate of 4 drm. per 1,000-lb. in a litre of raw
linseed oil should be given. For the removal of the mature females an enema
of strong quassia infusion may be given. Mercuric or carbolic ointment