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Parasitic Environment and Plan of Control.
' Broadly speaking ', he said, ' one would have to determine how long
the larvae and eggs of the various species of worms involved live in
manure piles, in spread manure, in closely packed manure ; the effect of
sunlight, of moisture, of various chemicals, the chemicals in turn being of a
nature not to injure the fertilizer value of the manure. There are
practically no data on this and little could be surmised without such data'.
Since that was written a considerable amount of investigation has been
carried out on this subject—chiefly in Dr Hall's own department in the
United States and in the Institute of Parasitology in Canada. It may be
considered under the following headings :
A. i. MANURE TREATMENT
(a) Storage.—The prompt daily collection of all manure in the stables is
an essential routine in farm practice and if correctly carried out is a valuable
preventive measure. If this manure were stored in a proper container for
a sufficient length of time, without any other treatment, all helminth eggs and
larvae would be destroyed. Unfortunately, in all cases investigated, this
time factor is too long to be practical and resource to additional methods is
necessary.
(b) Heating.—In piles of horse manure, all eggs and larvae of the strongyle
type are destroyed in four days by the natural heat generated, with the ex-
ception of those in the outer six inches. As a temperature as high as 107°F.
is generated in the central zone, all other parasites should be destroyed also,
although we are without definite knowledge of this. If the manure is confined
within wooden boxes—either above or below the ground—all except the outer
layer of three inches becomes hot enough to destroy the parasites, while
if the wooden boxes are double-walled with sawdust between, all are killed
in a week. Experiments with artificial heat, have shown that steam, at 15
lb. pressure, destroyed in 30 minutes all eggs and larvae in a special manure
box.
While these data enable manure to be effectively sterilized, they have,
with the exception of the first, the disadvantage of requiring special apparatus.
This entails expense and limits their application to well-equipped stables.
However, a compact manure pile, which has the outer six inches turned in
every five days or so, will undoubtedly kill a very high percentage of the eggs
and larvae.
(c) Drying.—This is a method which is only occasionally possible, and
the drying of large quantities of manure is practically confined to countries
with a hot, dry climate where dried dung is used as fuel, or in the army in
countries like Egypt where its value is secondry to military conditions, and
it may be spread out in the hot sun. In the latter case, however, immediate
daily drying is essential, as only the eggs and pre-infective stages are easily
destroyed by this method. Drying is of some value also in destroying larvae
on bare ground. Burning of manure is the logical extension of drying it,
but this is seldom practical.
In a rather different way this method has been used to combat the lung
and intestinal nematodes of silver-foxes in Canada. There the animals are
raised on floor-boards which are easily kept dry by being roofed. This in-
hibits development of the eggs and larvae of the forms so effectively that it