They cause swellings about the size of pigeons' eggs, each swelling having
a small hole in the center, which has been punctured in the skin by the
warble to enable it to breathe. Through this hole the warble leaves the
back of the cow when it has completed its parasitic stage of development,
at which time it measures nearly an inch in length.
The full-grown larvÊ begin to leave the backs of the cattle early in the
year, and in northern latitudes the last leave before the middle of July.
After leaving the backs of the cattle they burrow into the ground, lie
quiescent for about a month, and become transformed into mature flies. In
northern latitudes the mature flies of the species _H. lineatum_ may be
observed during April and May, and those of the other species during June
and July.
The damage caused by warbles includes injury to stampeding cattle
frightened by the fly, decreased milk flow and diminished growth in
infested animals, and injury to hides, the last item being especially
serious.
_Treatment._--The best method of control known at present is to extract the
warbles from the backs of cattle and kill them. If they are almost ready to
leave the cattle, they may be squeezed from the backs with the fingers.
Forceps are useful in removing the warbles, but it is important to be
careful in extracting warbles not to crush them, as the body juices of
these parasites are sometimes poisonous to cattle if absorbed into their
circulation. In the South herds may be examined in November or early in
December and once a month during the next two or three months. In the North
the first examination may be made six weeks to two months later, with two
or, better, three following examinations at intervals of a month. If this
procedure is carefully carried out there will be a noticeable diminution of
warbles the following year, and if persisted in the warble can be almost if
not completely eradicated. Where an entire community follows up the
practice of removing and destroying warbles, the results are highly
beneficial.
As a result of recent studies by various investigators it appears that the
tiny grubs, newly hatched from the eggs, may gain entrance to the body by
penetrating directly through the skin. Many observers, however, have held
that the eggs or newly hatched larvÊ are taken into the mouth by the cattle
licking themselves. It is possible, as in the case of several other
parasites, that both modes of infection may occur and that the larvÊ may
gain entrance to the body either by penetrating the skin or by being
swallowed. From the evidence at present available it seems likely that the
usual mode of entrance is through the skin. Irrespective of the mode of
infection, the larvÊ evidently wander extensively through the tissues of
the body, developmental stages being found in considerable numbers in the
wall of the esophagus during the fall of the year. They have also been
found in the spinal canal and in various other locations. Finally, about
January they appear beneath the skin of the back, forming the well-known
swellings. The posterior end of the grub is near the small opening in the
hide, through which the grub breathes and discharges its excrement, and
through which, when its development is complete, it finally escapes. The
anterior end of the grub is at the bottom of the tumor, where the mucus
collects upon which it feeds. By spring or early summer the grub is full
grown and forces its way out of the skin, falling to the ground, into which
it burrows for a short distance and transforms into the pupal stage. In
about a month the mature fly emerges.
It has lately been discovered that a second species of warble fly
(_Hypoderma bovis_) common in Europe is of not uncommon occurrence in
Canada and the northern part of the United States, whereas it was formerly
supposed that the ox warbles of this country were all of the one kind. The
general appearance, life history, and effects of the European species are
much the same as those of the American form.
Grubs weaken cattle, cause them to fall off in flesh and milk, and decrease
the value of the hide. The beef in the immediate vicinity of a grub becomes
slimy and of a greenish color, and is known to the butchers as "licked
beef."
The total loss to this country on account of the warble fly is estimated at
$35,000,000 to $50,000,000 a year, at the least, and may amount to
considerably more.
_Treatment for warbles._--During the winter and spring examine the cattle
for the presence of warbles. By passing the hand over the backs of the
animals the swellings marking the location of the grubs may be readily
found. Pressure properly applied to the swellings will cause the grubs to
"pop out" if they have reached a late stage of development. They may be
more easily removed by means of slender forceps inserted into the opening
of the warbles, and a still more certain method of removing them,
particularly if the lumps are still very small, is to cut into the
swellings with a sharp knife or bistoury, after which they may be pressed
out. Care should be taken to crush all grubs removed, so as to prevent the
possibility of their further development and transformation into flies. In
order that none may escape it is advisable to examine the cattle every two
weeks during the late winter and spring, at each examination removing the
grubs which have developed sufficiently to cause perceptible swellings.
Another method of treatment is to force grease or oil into the openings of
the warbles, which kills the grubs. This method is less certain than that
of removing the grubs, and has the further objection that the dead grubs
remain beneath the skin.
Cattle may be treated during the summer with fly repellents (p. 502) to
keep off the warble flies. The efficacy of repellents against these flies
is probably, however, not very great.
In localities where the character of the cattle industry is such as to
render practicable the systematic examination of cattle and the removal of
the grubs--that is, where the herds are comparatively small and subject to
the close supervision of the owners--it is possible, by the exercise of a
little care and with very little effort on the part of the cattle owners,
provided they work together, each doing his share by seeing to the removal
of grubs from his own cattle, so that as few as possible survive to
transform into flies, to reduce the number of grubs within one or two
seasons almost, if not entirely, to the point of extinction.
Investigations not yet completed indicate that grub eradication may
sometimes be accomplished by the use of arsenical dips, which are
extensively used at the present time for destroying cattle ticks. (See p.
497.) It is possible that the destructive action of arsenical dips upon
warbles is more or less dependent upon the fact that arsenic is stored up
in small quantities in and upon the skin of cattle that are repeatedly
dipped in arsenical dips. The arsenical dip appears to act, not upon the
well-developed grub beneath the skin, but upon the eggs or the newly
hatched larvÊ, probably the latter. Accordingly the dipping of cattle to
destroy grubs should be carried out during the fly season and repeated
treatments should be given every two or three weeks, as in dipping cattle
to eradicate ticks.
[Illustration: FIG. 6.--The warble fly (_Hypoderma lineatum_): _a_,
adult female; _b_, eggs attached to a hair, ◊ 25; _c_, larva as seen
in egg; _d_, larva from esophagus of an ox; _e_, later stage of larva
from beneath the skin of the back; _f_, larva at the stage when it
leaves the back of cattle and falls to the ground--all enlarged
(after Riley).]
LICE.[16]
Cattle in the United States are commonly infested with three species of
lice, two of them sucking lice (_HÊmatopinus eurysternus_, the short-nosed
cattle louse, and _Linognathus vituli_, the long-nosed cattle louse),
commonly known as blue lice, and one biting louse (_Trichodectes
scalaris_), commonly known as the red louse.
The blue lice (figs. 7 and 8) suck the blood of cattle and are more
injurious than the red lice (fig. 9). Unless very abundant the latter cause
little injury. If numerous they irritate and worry their host probably more
by their sharp claws than by their bites, as their food seems to consist
entirely of particles of hair and dead skin.
Cattle lice reproduce by means of eggs or nits (fig. 10) which they fasten
to the hair. The blue lice infest chiefly the neck and shoulders; red lice,
when present, may be found almost anywhere on the body, but are usually
most numerous on neck, shoulders, and at the root of the tail.
On account of the itching caused by the lice, infested cattle rub against
posts, trees, etc., and lick themselves, the hair sometimes coming out and
the skin becoming thickened so that mange may be suspected.
_Treatment for lice._--Cattle may be treated for lice by means of hand
applications, spraying, or dipping. Dusting powders sold under various
trade names are of value in helping to hold lice in check when the weather
is too cold for dipping or spraying. The application of greases and
insecticidal liquids by hand is fairly effective and practicable in cases
in which there are only a few animals to be treated. The following remedies
have proved effective when applied by hand, the treatment being repeated if
necessary in about 16 days: (1) Cottonseed oil and kerosene, equal parts;
(2) kerosene, 1/2 pint, mixed with lard, 1 pound; (3) crude petroleum; (4)
any of the dips recommended for use in dipping, and diluted in the same
proportions as for dipping. Oils or greases should not be used in very warm
or very cold weather. The remedies mentioned may be applied with a brush or
a cloth. They should be distributed in a thin, even coating over the
surface of the body, taking care that there is no excess quantity at any
point.
In spraying, any of the dips recommended for lice, properly diluted, are
applied by means of a spray pump over the entire body. Thorough wetting of
the skin and hair is important, and a second treatment should be given 15
or 16 days later.
When a considerable number of animals are to be treated the most
satisfactory method of destroying lice is by the use of a dipping vat. Two
dippings should be given 15 or 16 days apart. Dipping in the fall is good
insurance against risk of loss from lice during the winter. All animals in
the herd should be treated regardless of the number showing infestation.
Either coal-tar-creosote or nicotin dips may be used. These are sold under
various trade names. The directions for dilution given by the manufacturer
should be carefully followed. As coal-tar-creosote dips do not mix well
with all kinds of water, they should be tested with the water to be used
for making the solution by mixing some of the dip in the proper proportions
with the water in a clean and clear-glass bottle or jar. If an oily layer
or mass of globules collects either at the top or the bottom of the mixture
after standing an hour, the dip is not suitable for use with that kind of
water. Imperfectly mixed coal-tar-creosote dips are liable to poison
animals even when not used in stronger solutions than that recommended by
the manufacturers, and are also likely to be inefficacious.
The lime-sulphur dip, which is highly efficacious as a mange remedy, is of
little value for destroying lice, especially blue lice. The arsenical dip
used in tick eradication is a good louse remedy, but its use is not
advisable on account of its poisonous nature, except under the supervision
of capable persons who know how to use it and what precautions to take.
[Illustration: FIG. 7.--Short-nosed blue louse (_HÊmatopinus
eurysternus_) of cattle. Enlarged. (From Bureau of Entomology.)]
[Illustration: FIG. 8.--Long-nosed bluelouse (_Linognathus
vituli_) of cattle. Enlarged. (From Bureau of Entomology.)]
[Illustration: FIG. 9.--Red louse (_Trichodectes scalaris_) of
cattle. Enlarged. (From Bureau of Entomology.)]
[Illustration: FIG. 10.--Egg of short-nosed blue louse
(_HÊmatopinus eurysternus_) attached to a hair. Enlarged. (From
Bureau of Entomology.)]
MANGE, ITCH, SCAB.[17]
Cattle are subject to four kinds of mange, of which common mange or
psoroptic mange is the most important.
PSOROPTIC MANGE.
Psoroptic mange of cattle is caused by small mites (fig. 11) which multiply
rapidly and are spread from diseased to healthy cattle by bodily contact,
or by pens, stables, railroad cars, etc., recently occupied by mangy
cattle. The mites attack the skin and cause it to become thickened and
covered with crusts and scabs, with a consequent loss of hair. Intense
itching accompanies the disease, and affected cattle are more or less
constantly rubbing and licking themselves. Psoroptic mange commences at the
root of the tail, or on the neck, or withers, and gradually extends over
the back up to the head, over the sides, and may finally affect nearly the
entire body except the legs. In serious cases the skin may become
ulcerated; the animals are greatly weakened and emaciated, and finally die.
By taking scrapings from the edges of scabby patches and placing them on a
piece of black paper in a warm place the mites may be seen as tiny white
objects crawling over the paper, more distinctly if a magnifying glass is
used. Mange may be confused with lousiness, ringworm, or with any condition
in which there is itching or loss of hair, but if mites are found there is
no question of the diagnosis. The disease is worse during cold, wet
weather. Mangy cattle when on good pasture during the summer often seem to
recover, but in the fall the disease again appears in a severe form.
_Treatment._--The most generally used and most satisfactory method of
treating cattle mange consists in dipping the animals in a vat filled with
a liquid of such nature that it will kill the parasites without injuring
the cattle. Vats for dipping cattle are built of wood, stone, or concrete,
and vary in length from 30 to 100 feet or more. They vary in width from 3
to 7 feet at the top and 1-1/2 to 3 feet at the bottom, and the depth may
be from 7 to 10 feet. A narrow chute through which the cattle are driven
leads to one end of the vat, where a steep slide pitches the cattle into
the dipping fluid, through which they swim, and climb out of the vat at the
other end, which is built sloping and provided with cross cleats to give
the animals a foothold. A draining pen with floor sloping back toward the
vat is generally provided. The dip should be used warm, 100∞ to 105∞ F.,
and the cattle should be held in the vat for two minutes to insure thorough
action of the dip. The head of each animal should be ducked at least once.
Care should be taken that the vat contains a sufficient depth of fluid to
swim the animals to be dipped. The dipping fluid may be heated from a steam
boiler by pipes or hose, or water heated in large iron cauldrons or tanks
may be used for charging the vat, and hot water with a proper quantity of
dip added from time to time as the dipping fluid becomes cool.
If crude-petroleum dips are used, one dipping is usually sufficient, and
the dip is used cold. Crude-petroleum dips are rarely used for common
mange, but are of special value for sarcoptic mange, which is cured with
difficulty by the ordinary dips. In the treatment of ordinary mange with
lime-sulphur or nicotin dips two dippings are necessary, the second dipping
being given 10 to 14 days after the first. The second treatment is
necessary to kill the few parasites which sometimes escape at the first
treatment, either in the egg stage or as fecundated females.
[Illustration: FIG. 11.--Mite which causes psoroptic scab of sheep.
Enlarged about 100 times. The mite of psoroptic cattle mange is almost
identical in appearance.]
LIME-SULPHUR DIP.
The lime-sulphur dip is made in the proportion of 12 pounds of unslaked
lime (or 16 pounds of commercial hydrated lime--not air-slaked lime), 24
pounds of flowers of sulphur, and 100 gallons of water.
_Directions for preparing 100 gallons of dip._--Weigh out the lime, 12
pounds (or hydrated lime, 16 pounds), and sulphur, 24 pounds. Place the
unslaked lime in a shallow, water-tight box similar to a mortar box, or
some other suitable vessel, and add water enough to slake the lime and form
a lime paste or lime putty. Sift into this paste the flowers of sulphur and
stir well; then place the lime-sulphur paste in a kettle, boiler, or tank
containing 30 gallons of water, the water being first heated nearly to the
boiling point. Boil the mixture for two hours at least, stirring
frequently; add water occasionally to maintain the original quantity. Allow
the mixture to settle in the tank or draw the entire contents of the kettle
or boiling tank into a large tub or barrel placed near the dipping vat and
provided with a bunghole about 4 inches from the bottom, and then allow
ample time to settle--from two to three hours or more if necessary. When
fully settled, draw off the clear liquid into the dipping vat, taking care
not to allow any of the sediment to accompany it, as the sediment is liable
to render the dip unnecessarily caustic. The clear liquid thus obtained
requires only the addition of sufficient clear warm water to bring the
total up to 100 gallons. Flowers of sulphur must be used and the lime must
be of good quality.
The dipping bath should be used at a temperature of 100∞ to 105∞ F., and
for official dippings must be maintained at all times at a strength of not
less than 2 per cent of "sulphid sulphur" as indicated by the Bureau of
Animal Industry field test for lime-sulphur baths.
NICOTIN DIP.
The nicotin dip is made with sufficient extract of tobacco, or nicotin
solution, to give a mixture containing not less than five one-hundredths of
1 per cent nicotin and 2 per cent flowers of sulphur. Sufficient nicotin
would therefore be furnished for 96 gallons (about 800 pounds) of dip by 1
pound of a 40 per cent solution of nicotin. The formula for this dip would
be: Nicotin, four-tenths of a pound; flowers of sulphur, 16 pounds; water,
96 gallons.
To calculate how much nicotin solution or extract of tobacco should be used
for 96 gallons of water, divide the quantity of nicotin required in the dip
by the proportion of nicotin in the extract. For example, suppose the
nicotin solution contains 25 per cent nicotin, we have 0.40 ˜ 0.25 = 1.6.
Therefore in this case it would require 1.6 pounds of nicotin solution for
the 96 gallons of dip. Or, if a tobacco extract is used, having, for
example, 2.4 per cent of nicotin, the formula would be as follows: 0.40 ˜
0.024 = 16.66, and therefore 16.66 pounds would be required for 96 gallons
of dip. Do not use any preparation the strength of which is not given on
the outside of the package.
In preparing these dips the nicotin solution and sulphur should be mixed
together with water before adding them to the water in the dipping vat. On
no account should the dip be heated above 110∞ F. after the nicotin
solution is added, as heat is liable to evaporate the nicotin and weaken
the dip.
For official dippings the dipping bath should be used at a temperature of
100∞ to 105∞ F. and at all times must be maintained at a strength of not
less than five one-hundredths of 1 per cent nicotin as indicated by a field
test approved by the Bureau of Animal Industry.
A homemade nicotin dip may be prepared as follows:
For each 100 gallons of dip desired, take 21 pounds of good, prepared
tobacco leaves; soak the leaves in cold or lukewarm water for 24 hours in a
covered pot or kettle; then bring the water to near the boiling point for a
moment, and, if in the morning, allow the infusion to draw for an hour; if
in the evening, allow it to draw overnight; the liquid is next strained
(pressure being used to extract as much nicotin as possible from the wet
leaves) and diluted to 100 gallons per 21 pounds of tobacco. This dip
should be used as fresh as possible, as it contains a large amount of
organic material which will soon decompose.
CRUDE-PETROLEUM DIPS.
Crude-petroleum dips, which are valuable for the treatment of sarcoptic
mange, are not often used for the treatment of psoroptic mange or of
chorioptic mange, oily dips being liable to injure animals, especially if
they are moved rapidly soon after treatment, if they are exposed to bright
sunshine, or if they become chilled. Besides unprocessed crude petroleum,
processed petroleum from which the gasoline and other light hydrocarbons
have been removed may be utilized in the treatment of cattle for mange,
particularly sarcoptic mange. There are a number of proprietary brands of
crude-petroleum dips on the market, consisting of processed crude petroleum
with other substances added, mainly lighter oils to give the dip a suitable
consistency. In dipping cattle in crude-petroleum dips fill the vat with
water to within 1 foot or 18 inches of the dip line and then add the oil
until the surface is flush with the dip line. The oil floats on the water,
and as the animals pass through the vat their bodies become coated with
oil.
CHORIOPTIC MANGE.
Chorioptic mange, due to a species of mite different from that causing
common cattle mange, is confined almost entirely to the region at the root
of the tail and if not treated may persist for years. The treatment is the
same as for psoroptic mange.
SARCOPTIC MANGE.
Sarcoptic mange, frequently called "barn itch," is caused by a mite very
similar to that which causes itch in human beings. It commonly affects the
head and neck, but may also occur on various other parts of the body. Bulls
are particularly liable to be affected with this form of mange. Cattle may
become infected not only from other cattle, but also from horses, goats,
dogs, sheep, and hogs. As a rule sarcoptic mange in any species of animal,
if acquired from an animal of another species, is likely to run a short
course and tend toward a spontaneous recovery.
The treatment likely to be most efficacious is that of dipping in a
crude-petroleum dip, one treatment as a rule being sufficient. If
lime-sulphur dip is used, four or five successive treatments, or even
more, at weekly intervals, may be necessary before a cure is effected.
DEMODECTIC MANGE.
Demodectic mange, which is caused by a small parasite that lives in the
hair follicles, causing pustules, especially on the neck and shoulders,
occurs occasionally among cattle in this country and is of importance on
account of the injury to the hide. When tanned, hides infested by this
parasite are pitted, the pits, in some cases, being so deep that they form
holes. No practicable treatment is known for this disease.
TICKS.[18]
About 10 species of ticks have been reported as parasites of cattle in the
United States. The most common and most important is the species known as
_Margaropus annulatus_, which transmits Texas fever. Information concerning
this tick and Texas fever has been given elsewhere in this volume (p. 475).
The spinose ear tick (_Ornithodoros megnini_) is frequently found in the
ears of cattle in the western part of the United States, and is of common
occurrence also in the ears of horses, dogs, cats, etc.
When its parasitic stage of development is completed the ear tick leaves
its host. Mating between the sexes occurs after the ticks have cast their
skins following the abandonment of their host. They usually crawl up some
distance from the ground and secrete themselves in cracks and crevices in
trees, walls of buildings, etc., where the females deposit their eggs.
After the eggs hatch, the larval ticks, which emerge from them, when they
succeed in finding a host, enter the ears and gradually develop to the
stage at which they are ready to leave the host animal. The females may
live several months, or even years, if they do not find mates. After mating
they may deposit their eggs intermittently. Hatching of the eggs may occur
as early as 10 days after deposition. The larvÊ may live for 80 days
without a host. The parasitic period has been observed to vary from about
two to about seven months.