DISEASES OF THE SKIN
GENERAL DISCUSSION.--The two layers that form the skin are the _epidermis_
and the _derma_. The cells of the outer layer or epidermis are of two
kinds. The superficial portion is formed by horny, flattened cells and the
deeper by softer cells. This layer of the skin varies greatly in thickness
in the different species. The derma is composed of some muscular fibres
interwoven with the connective-tissue fibres. It contains the roots of the
hair follicles, sweat and oil glands. The external face which is covered by
the epidermis shows a multitude of little elevations. These are the
vascular and nervous papillae. In addition, it shows openings through which
the hairs and the skin glands pass. The inner surface is united more or
less closely to the muscular or underlying tissue by a layer of fibro-fatty
tissue.
_The appendages of the skin_ are the hairs and horny productions. The horny
productions comprise the horns, chestnuts, ergots, claws and hoofs.
_The hair varies_ in length, thickness and coarseness in the different
species, and the different regions of the body. In addition, breeding,
care, heat and cold may cause marked variations in the thickness of the
coat. Exposure to cold causes the coat to thicken. High temperatures cause
the short hairs to drop out and the coat to become thin.
Diseases of the skin may be _classified as parasitic_ and _non-parasitic_.
Parasitic skin diseases are caused by animal and vegetable parasites.
Non-parasitic skin diseases are caused by irritation to the skin and
internal causes. Irritation to the skin may be either chemical, thermic or
mechanical. The internal causes may be due to an individual predisposition
together with digestive disturbances and the eating of feeds too rich in
protein. In this chapter parasitic skin diseases produced by insects will
not be discussed.
FALLING OUT OF THE HAIR AND FEATHERS.--Falling out of the hair and feathers
frequently occurs independent of parasitic diseases. This condition does
not occur as an independent disorder, but as a secondary affection. It is
due to faulty nutrition, and irritation to the skin. Intestinal diseases,
insufficient feed and feed of bad quality are common causes. Animals that
are fed a heavy ration, or that lie on dirty, wet bedding frequently lose
large patches of hair. Sheep that are dipped in late fall and early winter,
or exposed to wet, cold weather may lose a part of their fleece. It is not
uncommon for animals toward the latter period of pregnancy, or that sweat
freely, to lose patches of hair.
Falling out of the hair heals of itself within a few weeks.
_The preventive measures_ are of special importance in sheep and horses.
This consists in avoiding conditions that may lead to alopecia and in
correcting the diet. In horses the regions of the mane and tail should be
washed with soap, or rubbed with alcohol and spirits of camphor, equal
parts. Treatment should be persisted in for a long period if necessary.
URTICARIA, "NETTLERASH."--Urticaria is characterized by roundish elevations
that appear quickly and become scattered over a part or the whole surface
of the skin. They are caused by an inflammatory infiltration of the deeper
layers of the skin. Horses and hogs are most frequently affected.
_The causes_ of urticaria are irritating juices of certain plants,
secretions of flies, ants and some caterpillars, irritating drugs,
scratching, sweating and the action of cold on a warm skin. It has been
observed in connection with the feeding of certain leguminous feeds and
digestive disturbances. Horses that are fat, or putting on flesh rapidly,
seem to be predisposed to this disorder. Urticaria may occur in certain
infectious diseases.
_The characteristic symptom_ is the formation on the skin of roundish
elevations or "hives." There may be an elevation of body temperature and
partial loss of appetite. Small animals may act restless and show evidence
of itching or pain. This symptom is very common in hogs. The eruption may
last only a few hours or a few days, or, because of the animal's scratching
or rubbing the part, the skin may become scabby and small pustules form.
An important _preventive measure_ is to avoid the use of agents capable of
irritating the skin and producing urticaria when treating parasitic skin
diseases. It is very advisable to give the animal a saline cathartic (Epsom
or Glauber's salts). The skin may be washed with cold water, or a weak
water solution of permanganate of potassium.
ACNE, "SUMMER RASH."--In this skin disease the oil glands and hair
follicles are inflamed and sometimes infected with pus germs. This results
in skin eruptions varying in size from the point of a pin to about a
quarter of an inch in diameter. This inflammation is most prominent during
the warm weather.
_The causes_ are local irritation to the skin from lying on filthy floors,
sweating and irritation from the harness. According to some writers, pus
germs are the only cause, the mechanical agents merely aiding in the
production of the infection.
The face, side of the neck, shoulders, back and sides of the trunk and
quarters are the usual seats of disease. The pimples or nodules may
disappear within a few weeks, or persist throughout the warm season. The
eruption may disappear without leaving scars, or suppuration occurs and
small bald spots result.
_The treatment_ consists in removing the cause of the disease and cleaning
the skin with antiseptic washes. The surroundings of the animal must be
kept clean and a good bed provided. If possible, the horse should be laid
off from work as soon as the condition is noted. Washing the part with a
weak water solution of permanganate of potassium may be practised daily.
Fowler's solution of arsenic may be given. This may be given with the feed.
ECZEMA.--This is an inflammation of the vascular capillary bodies and the
superficial layer of the skin. There may be marked inflammatory exudate,
causing the surface of the skin to become excessively moist and more or
less itching. Redness, vesicles and pustules may characterize the
inflammation. In the chronic form the skin may become thickened and greatly
changed in structure.
Eczematous inflammation of the skin may occur in all domestic animals, but
it is most common in the dog. In the horse local eczema (scratches) is
common.
The most frequent _cause_ is external irritation. Accumulations of filth on
the skin and continual wetting of the part are common causes. Mechanical
causes are rubbing, pressure, the action of the sun's rays and chemical
irritants. Internal causes, such as catarrhal diseases of the stomach and
weakness and emaciation from disease, may act as direct or predisposing
causes. Tender-skinned animals seem to be predisposed to the disease.
_The symptoms_ vary in the different species of animals. In the horse the
thin skin posterior to the fetlock and knee, in front of the hock and on
the under side of the body is most commonly inflamed. Moisture and dirt
seem to be the most common causes. Eczema may involve the skin covered by
the mane and tail in animals that are not properly groomed and inclined to
rub or scratch. Cattle may suffer from eczematous inflammations in the
region of the forehead, back of neck and base of tail. A very common form
of the disease involves the space between the toes. Sheep frequently suffer
from inflammation of the skin over the fetlock region. The skin of animals
having long fleeces, or heavy coats of hair that become wet at a time when
there is no opportunity to dry out quickly, may become inflamed. Dogs are
commonly affected by the acute and chronic forms of eczema. Eczema of swine
is limited mostly to young hogs. It is rather rare, excepting in hogs that
are pasturing on certain kinds of clover and rape, or on muck lands.
The inflammation is accompanied by a marked tenderness and itching, and the
animal licks and scratches the part. This increases the extent of the skin
lesions. The skin appears moist, later dirty, scabby and thickened. Cracks
and pustules may form. Gangrene and sloughing of the skin may occur.
_The treatment_ is both preventive and curative. Cases of eczema caused by
filth and wetness can be prevented by giving the necessary attention to
keeping the skin clean and not allowing animals access to muddy, filthy
places. Keeping the bed clean and regulating the diet are important
preventive measures. Before the inflammation can be successfully treated
the cause must be removed.
In acute eczema it is advisable to protect the part against water, filth
and air. Powders and ointments may be used during the early stages of the
inflammation. Two parts boric acid, four parts flour, and one part tannic
acid may be dusted over the moist surface. One part zinc oxide and twelve
parts vaseline is a useful ointment. Scratching the part should be
controlled in every case by muzzles, collars and bandages. Dirt and scales
may be removed from the skin by washing with cotton soaked in lime water or
linseed oil. The animal should receive laxative doses of Glauber's salts or
oil every few days. A simple, easily digested ration should be fed. The
following mixture may be applied in obstinate cases: oil of tar and soft
soap, two parts each, and alcohol one part.
COMMON FEED RASHES.--This title includes inflammation of the skin caused by
pasturing on buckwheat, certain clovers and rape, together with moisture
and sunlight.
Green, flowering buckwheat is more dangerous as a feed for stock than is
the grain or straw. Clovers and rape are not as dangerous a feed. The
actual cause of the skin becoming inflamed is not known.
The skin in the regions of the face, ears, neck, lower surface of the body
and limbs becomes red and covered with vesicles. Later, scabs and pus may
form.
_The treatment_ consists in changing the ration and keeping the animals out
of the sun, or long grass and weeds for a few days. This is all the
treatment required in most cases. It may be advisable to administer a
physic. If pus and scabs form, the part should be cleansed daily with a one
per cent water solution of permanganate of potassium.
HERPES (FUNGOUS SKIN DISEASE).--This is a contagious disease of the skin
caused by thread fungi, _Tricophyton tonsurans_ and _epilans_, which
develop in the skin in localized areas, causing vesicles, scabs or scales
to appear, and the loss of the hair over the part. This skin disease occurs
in all domestic animals, but it is most commonly met with in cattle. It
usually affects young cattle. It most commonly occurs in the region of the
face and neck. Thick, bran-like crusts form over the scattered areas of the
skin and the hair drops out or breaks off. The animals frequently rub the
infected area.
_Prompt treatment_ may prevent the spread of this disease in the herd. It
may be checked by quarantining the infected animals and scrubbing the
stalls, stanchions and walls with a disinfecting solution. Grooming the
infected animal should be discontinued. This skin disease responds most
readily to ointments. Flowers of sulfur one part and lard ten parts is
commonly used by stockmen. Sulfur-iodide ointment, or tincture of iodine
may be applied.
QUESTIONS
1. Give a general description of the skin.
2. Give the causes and treatment of falling of the hair.
3. What is urticaria? Give the treatment.
4. What is summer rash? Give the treatment.
5. What is "scratches"? Give the treatment.
6. What feeds produce rashes of the skin?
7. What fungus produces an inflammation of the skin in cattle? Give the
treatment.