Skin Disorders

Question 1

General skin disorders characteristics

Answer 1

-time of year
-itching
-crusts, scales, loss of hair
-1 location or multiple
-what structures are involved

Question 2

Causes of skin disorders:

Answer 2

-mange
-pediculosis
-onchocerca
-culicoides
-food allergy
-atopy
-dermatophytosis
-dermatophilosis
-folliculitis
-malassezia
-seborrhea
-pemphigus foliaceus
-papillomavirus
-habronema
-sarcoid
-sporotrichosis
-screwworm

Question 3

Papillomavirus

Answer 3

cutaneous papillomas (warts) are proliferative skin lesions caused by equus caballus papillomavirus type 1 (EcPV-1)

Question 4

What age does papillomavirus most effect?

Answer 4

most horses are <3 years old

Question 5

How is papillomavirus spread?

Answer 5

by fomites or close contact

Question 6

How long do papillomavirus warts last?

Answer 6

warts disappear spontaneously 1-6 months after they appear

Question 7

Clinical findings of papillomavirus

Answer 7

-warts on muzzle, lips, sometimes distal limbs, ears, eyelids, genitalia
-cauliflower-like appearance

Question 8

How is papilloma virus diagnosed?

Answer 8

obvious lesions, sometimes cutaneous biopsy to differentiate from verrucous sarcoids (older horses)

Question 9

How is papilloma virus treated?

Answer 9

resolves spontaneously
-it is difficult to determine if therapy actually helps

Question 10

When is treatment generally done for papillomavirus?

Answer 10

for esthetic reasons:
-freeze warts
-chemical cauterization
-surgical excision
-immunostimulants

Question 11

How can papillomavirus be prevented?

Answer 11

affected horses should be isolated
-disinfect the premises and equiptment

Question 12

What is dermatophilosis?

Answer 12

-rain rot
-mud fever
-dew poisoning

Question 13

What is dermatophilosis caused by?

Answer 13

Dermatophilus congolensis:
falcultative anaerobic
shares characteristics with bacteria and fungus (hyphae and zoospores)

Question 14

What is the natural habitat of dermatophilosis?

Answer 14

unknown

Question 15

How can infections of dermatophilosis spread?

Answer 15

crusts from infected animals can infect the same animal on a different spot and other animals

Question 16

What does the establishment of dermatophilosis infection depend on?

Answer 16

depends on the virulence of strain, health of horse, skin trauma, and moisture

Question 17

What happens when dermatophilosis infections start?

Answer 17

-zoospores germinate, producing hyphae under favorable conditions
-hyphae penetrate the skin
-hyphae breaks down and forms coccoid cells
-those cells are released from the crusts to infect new areas

Question 18

How does dermatophilosis survive?

Answer 18

D. congolensis break keratin and function at a wide pH range, enabling the disease to survive in inflammed skin

Question 19

Can D. congolensis infect intact skin?

Answer 19

no

Question 20

What makes skin susceptible to D. congolensis infection?

Answer 20

insects and ticks cause trauma making the skin susceptible to the infection

Question 21

What is one of the main causes of dermatophilosis?

Answer 21

moisture
-rain increases blood sucking flies, creates moist environment under hairs with low oxygen

Question 22

Clinical signs of dermatophilosis:

Answer 22

-lesions are exudative
-hairs are matted together forming thick crusts
-underlying skin under crusts is eroded, painful, and may bleed
-new lesions can be purulent and old lesions are dry and hairless

Question 23

Where is dermatophilosis often found?

Answer 23

-rump
-dorsal thorax
-face
(from heavy rainfall)
-saddle area (when pad rubs and injures the skin)

Question 24

How is dermatophilosis diagnosed?

Answer 24

cytology and clinical signs

Question 25

Treatment of dermatophilosis

Answer 25

-parenteral administration of antibiotics (penicillin, SMZ-TMP) -topical benzoyl peroxide shampoos (antibacterial and keratolytic, breaking down the crusts) (MTG, Kinetic products) -most horses recover after 1 month of being kept at a dry place

Question 26

Prevention of dermatophilosis:

Answer 26

-keep animals dry -don't share grooming tools -insect repellent -groom horse routinely to air out the skin

Question 27

Dermatophytosis

Answer 27

ringworm

Question 28

How long can fungus survive on an infected ringworm girth?

Answer 28

for 1 year

Question 29

Is dermatophytosis contagious?

Answer 29

yes by indirect and direct contact

Question 30

What % of horses with suspected ringworm actually have ringworm?

Answer 30

5% -majority are dermatophilus or staph infection of the skin

Question 31

What can lead to dermatophytosis lesions?

Answer 31

abrasions of the skin (important in heartgirth area)

Question 32

What can predispose horses to dermatophytosis?

Answer 32

stress

Question 33

What happens to some horses after a dermatophytosis infection?

Answer 33

they develop a strong immunity against it, they clear the infection and never develop it again

Question 34

Lesion characteristics of dermatophytosis:

Answer 34

-may present with circular patches of alopecia -surrounded by erythema and scaling

Question 35

What may be observed in the early stages of dermatophytosis?

Answer 35

urticaria-like lesions

Question 36

Where are the most frequent sites of dermatophytosis?

Answer 36

girth and shoulder

Question 37

How is dermatophytosis diagnosed?

Answer 37

-cytology (bacteria, fungus) -skin scraping (fungus, mange, other mites) -histology (pemphigus foliaceus) -culture of fungus -determining what it isn't first

Question 38

How are most cases of dermatophytosis resolved?

Answer 38

spontaneously

Question 39

Treatment of dermatophytosis:

Answer 39

-topical: povidine-iodine, 2% lime sulfur dip, ketoconazole shampoos -bleach environment -spray horses that were in contact with the infected horse

Question 40

Is dermatophytosis zoonotic?

Answer 40

yes it can be passed to humans

Question 41

Why are ketoconazole shampoos not very effective?

Answer 41

they have to sit for awhile on the skin in order to work, they no longer work after getting rinsed off

Question 42

Urticaria (hives)

Answer 42

multiple plaque-like eruptions formed by localized edema (often develop and disappear suddenly)

Question 43

Is hives exogenous or endogenous?

Answer 43

both

Question 44

What can exogenous hives be produced by?

Answer 44

toxic irritating products of the stinging nettle, the stings or bites of insects, medications, or chemicals

Question 45

What can endogenous hives be produced by?

Answer 45

after inhalation or absorption of ingested allergens

Question 46

What can hives be associated with?

Answer 46

intestinal parasites

Question 47

How can present as urticaria (hives) early in the disease?

Answer 47

-dermatophytosis (ringworm) -pemphigus foliaceus

Question 48

Clinical signs of urticaria (hives)

Answer 48

-plaques appear within a few minutes or hours of exposure to the causative agent -horses are often excitable or restless -skin lesions are elevated, round, flat-topped, and may be slightly depressed in the center -on any part of the body -lesions disappear as rapidly as they arise (usually within a few hours) -prognosis is favorable -fatalities are rare

Question 49

Clinical signs of severe cases of urticaria (hives)

Answer 49

-the cutaneous eruptions are preceded by fever, anorexia, or dullness -they may be found on the mucous membranes of the mouth, nose, conjunctiva, rectum, and vagina -death due to anaphylaxis

Question 50

What is the treatment of acute urticaria?

Answer 50

it usually disappears spontaneously

Question 51

Treatment of uticaria:

Answer 51

-dexamethasone -antihistamines (Rocover-Kinetic) -epinephrine to combat anaphylactic shock -lesions will return if the allergen is not eliminated