Lesson
11
Common
Skin Diseases of the Horse &
Administration
of Medication to the Horse
Skin
Diseases
Girth Itch (ringworm)
1.
Very
common fungal skin disease in young stabled horses
2.
Highly
contagious through contact with other horses or tack
3.
Loss
of hair and itching
4.
circular
of large patchy areas affected
5.
control
includes disinfecting tack and grooming equipment
6.
treatment with topical antifungal
products (tamed iodine, clorhexidine, benzalkonium cloride, diluted
bleach solution. Bathe with Enilconazole
solution. Possibly oral antifungal (griseofulvin)
Biting
Gnats (culicoides) and Summer Itch (onchocerca)
1.
allergy
associated
2.
Itching
and hair loss in withers, tailhead area and ventral
abdomen
3.
Control
includes insect control, management procedures(stabling during bad gnat times
–early morning and late evenings)
4.
Ivermectin will destroy onchocerca
mircofiliria
Rain
Rot (Rain Scald, dermatophilus)
1.
Bacterial
skin infection which appears as a pattern of rain drops over the back, rump and
cannon bone of a horse
2.
Usually
appears during hot, humid or rainy weather
3.
Contagious;
may be spread by tack, grooming tools, caretakers and insects
4.
The
patches involved are circular and patchy which can be pulled up easily and a
purulent moist wound is found underneath.
5.
Treatment
consists of antibacterial shampoos, disinfecting tack and equipment. Avoid use
of ointments as the goal is to keep lesions dry. Keep animal dry.
Equine
Pastern Dermatitis (Scratches, Greasy Heel, Mud Fever)
1. Can affect any breed, but very
problematic in draft breeds, especially with the heavy-feathered legs.
2. Located on the caudal aspect of the
pasterns, but can spread to the front of pastern and fetlock if not treated. May affect only one limb.
3.
Three forms:
a. mild form: symptoms are
alopecia (hair loss), scales, crust with potential epidermal hyperplasia.
Pruritus and pain are variable.
b. exudative form: symptoms are:
erythema, erosion, alopecia, and serous to purulent crusting dermatitis.
Epidermolysis and vasculitis are often involved.
c. chronic proliferative form:
symptoms are: elevated wart-like eruptions (verrucous pododermatitis),
excessive granulation tissue (fibroblastic proliferation) that becomes cornified (skin turns into a horny material). Nodular
proliferations of hyperkeratosis (thickening of outer skin) and lichenification (thick hard leather-like skin) occur.
Fissures and papillomatous (benign tumors that
resemble cauliflower) may develop.
4. Causes are not understood,
but three basically recognized:
a.
photosensitization: seems to effect white skinned lower legs; exposure to
clover, St. John’s wort, buckwheat, perennial rye grass – this form can also
affect the muzzle. May lead to liver disease.
b. chronic progressive
lymphedema: primarily in draft or horses related to draft breeds. Research at
University of California, Davis is focusing on the possible abnormal
functioning of the dermal lymphatic system.
c. pastern leukocytoclastic
vasculitis: the least understood of the three, possibly caused by immunocomplex (breakdown of immune system) in the blood
vessels of the distal limbs (below knee or hock).
5. Diagnose by
ruling out mange by conducting a scrape. Biopsy; culture; microscopic examination
of skin and hair; complete blood count
6.
Treatment: Type must be identified, and then treated accordingly. Management: all horses affected must be kept
clean and dry. (Avoid dew, moisture, mud, manure, urine). Avoid bedding that
might contain oils or chemicals. Clip hair. Use antibacterial shampoos
containing the active
ingredients benzoyl peroxide (2%), ethyl lactate, or chlorhexidine (2%).
Steroids, antibiotics, antifungal treatment, the use of anti-parasitic
solutions may be needed. Treat any secondary
infections with antibiotics. Remove horses with photosensitization from
pastures.
External Parasites
Lice
1.
Minute
organisms found in the hair causing itching
2.
Control
includes good management procedures (clean environment and prevent overcrowding)
3.
Treatment
involves using an insecticidal dust labeled for treating horse lice, usually permethrin is the active ingredient.
4.
Wash
and treat all tack and equipment. Use
extremely hot water.
TICKS
Ticks
1.
Body
ticks and spinous ear ticks (Otobius megnini)
2.
Causes
anemia and death if extensive infestation.
3.
Ear
ticks can travel into the ear canal, infestations may cause paralysis.
4.
Secondary
infections possible with both types of ticks.
5.
Treatment:
never remove tick with bare hands, use tweezers. Do not use a hot match.
Insecticides should be used in conjunction with removing the ticks. Contact
veterinarian for severe cases.
6.
Prevention:
keep horses away from habitat where ticks thrive – tall grass and weeds. Keep pastures mowed.
Mange
(Mites)
1.
Four
types: sarcoptic, psoroptic,
chorioptic and demodectic
a. sarcoptic:
rare, but the most severe type. First signs are generally lesions on the head,
neck and shoulders. First symptoms are papules
(small bumps, not fluid filled) and vesicles (fluid-filled). Alopecia (loss of
hair) and crusting eventually develops. Skin becomes lichenified
(tough and leather-like), folds may appear. If the mange is not treated, the
lesions may spread. Loss of weight, weakness, and anorexia (not eating) is the
result of the spreading disease. Biopsy is usually needed to diagnose sarcoptic mange. (Skin scrapings do not show sarcoptic mites easily.)
Treatment: hot lime sulfur spray or dip.
Repeat 12 days if needed. Off-label treatment: two doses of oral ivermectin at 200 mcg/kg given 14 days apart (field
studies), or a single treatment of oral moxidectin at
400 mcg/kg
b. psoroptic:
lesions generally appear on the thickly haired areas of the body. Head shaking may present. Pruritus (itching)
is a symptom. Lesions start as papules and alopecia and develop into thick,
hemorrhagic crusts. Skin scrapings can detect the presence of the mites.
Treatment: hot lime sulfur spray or dip.
Repeat 12 days if needed. Off-label treatment: two doses of oral ivermectin at 200 mcg/kg given 14 days apart (field
studies), or a single treatment of oral moxidectin at
400 mcg/kg
c. chorioptic
(leg mange): Most common form of mange in horses. Not the same as “greasy
heel”, scratches or mud fever. Pruritus affects the distal (everything below
the knee or hock) limbs. Papules are
seen first, followed by alopecia, crusting, and thickening of the skin. A moist
dermatitis of the fetlock develops in chronic cases. Infested horses may stamp their
feet or rub one foot against the opposite leg or object. The disease will be chronic if not treated.
Treatment: Clip hair. Hot lime sulfur spray or dip. Repeat 12 days if needed. Off-label
treatment: two doses of oral ivermectin at 200 mcg/kg
given 14 days apart (field studies), or a single treatment of oral moxidectin at 400 mcg/kg
d. demodectic:
mites infest the hair follicles and sebaceous glands. Rare in horses. Alopecia, scales and nodules may form. Has
been associated with PPID (pituitary pars intermedia dysfunction) and chronic
corticosteroid treatment. Treatment: demodectic
mange usually resolves itself, but because of the risk of a secondary infection
a veterinarian must be consulted. Other mange types must be ruled out/treated.
Other Mites:
1.
Trombiculidiasis (Chiggers, Harvest Mite): active in
summer and fall. Normally these mites
feed on rodents, but can travel to horses, humans and other animals as they are
found in the grass. Lesions consist of
severely pruritic papules and wheals on the face, lips, and feet. At the time
of diagnosis, a topical pyrethrin or pyrethroid labeled for horses can be used to kill any
remaining larvae still feeding. Symptomatic treatment with a glucocorticoid for
pruritus can be added to minimize further self-trauma and associated secondary
infections. Any secondary infections should be treated. Repellents may help
prevent infestation.
2.
Straw Itch Mite (Forage Mite): These mites usually feed on organic material in
straw and grain and can opportunistically infest the skin of horses. Papules
and wheals appear on the face and neck if horses are fed from a hay rack, and
on the muzzle and legs if fed from the ground. Pruritus is variable. Treatment
for trombiculidiasis may be used for straw itch mite
infestations.
Skin Tumors and Proud Flesh
Proud
flesh
(exuberant granulation tissue)
1.
contaminated
and poorly managed open wounds
2.
worse
in humid areas of the country
3.
good
wound care and pressure bandaging (for wound protection and pressure and immobility
of the area) help prevent proud flesh
4.
Copper
sulphate products can control proud flesh problems
5.
Surgical
removal may be necessary
Sarcoids
1.
The
most common type of skin tumor in the horse. Not considered life-threatening.
2.
Two
types: verrucous (grows slowly, may disappear) and fibroblastic (aggressive and
invasive)
3.
Verrucous
will look like a small, flat wart, with a crusty surface
4.
Fibroblastic
will have a raised bumpy surface, may bleed and ooze fluids if disturbed. May
rapidly grow into large angry looking masses.
5.
Possibly
caused by a virus, research continues.
6.
Treatment:
generally left alone unless they are located where they trouble the horse
(rubbing by tack), if they are open and sore (attracting flies, becoming
infected) or inhibiting the use of an eyelid. Surgical removal, laser removal,
freezing, chemotherapy, radiation or immuno-stimulant injections
Warts
1.
Normally
seen in young horses
2.
Usually
self limiting (they will go away on their own in about 30 to 60 days)
3.
Caused
by contagious virus
4.
Castor
oil or salycilic acid may help remove warts, possible
scarring
5.
removal
of some and spreading of the blood on some of the other warts has been known to
work.(immune response)
Melanoma on the parotid
salivary gland
Melanoma
1.
Tumor
(cancer) seen on mostly older, gray horses.
2.
Appearance:
firm growth will appear to be just under the skin, may or may not be covered
with hair. Hairless tumors will be dark black. Some may develop ulcers and/or
have an oily discharge. Often appears in clusters.
3.
Usually
seen around perineal area (anus). Other locations: under the tail, around the
lips, internally at the base of the ear (parotid salivary gland), guttural
pouches, eyes, external genitalia.
4.
May
spread to internal organs, progression is generally slow
5.
Treatment:
most veterinarians will advise monitoring the growth, they are slow growing.
Surgical removal is the primary method of treatment, but is left to the
discretion of the veterinarian and owner. Incomplete removal
6.
may trigger aggressive re-growth
or metastasis (spreading to other areas). Other treatments: cryonecrosis
(freezing), chemotherapy, radiation
EQUINE WOUND
HEALING PRODUCTS
Antibacterials
1. Nitrofurazone ointment, spray, and powder – Furacin,
topazone, furazone and
other generic products
2. Tamed
Iodine ointment and gel – Betadine, biozide
gel.(antifungal also)
3. Clorhexidine ointment and salve – Nolvasan
salve.(antifungal also)
4. Aluspray
5. Benzalconium Chloride based products _ Fungisan
( also anti fungal)
6. Other
prescription antibiotic ointments.
Stimulate Granulation
1. Scarlet
oil
2. Granulex –also contains enzymes for removing necrotic tissue
3. Tripzyme - also contains enzymes for removing necrotic
tissue
4. Cut N
Heal
Drying (astringent) agents
1. Blue
or purple wound spray (Gentian violet)
2. Wonder
Dust
Proud flesh inhibitors
1. Copper
sulfate powders and ointments – Proudsoff Proud X
2. Iodine
– formalin solutions
Other Misc. Wound Products
1. Gall
Salve
2.
3. Ichthammol
– good for drawing abscesses.