Equine Derm Flashcards
Protein deficient diets can result in what type of changes in skin and hair?
hyperkeratosis, cutaneous atrophy, pigmentary disturbances, dry/dull/brittle hair
Which cytokine(s) is/are decreased in the horse during the summer?
IFN-gamma
Sarcoptes scabei
Histopathology of sarcoidosis
nodular to diffuse sarcoidal granulomatous dermatitis that affects all portions of dermis, multinucleated histiocytic giant cells
What are vectors for Onchocerca cervicalis?
Culicoides spp. gnats & mosquitoes
Histopathology characteristics of erythema multiforme
hydropic interface dermatitis, apoptosis of keratinocytes, satellitosis of lymphocytes and macrophages, pigmentary incontinence, dermal edema, purpura (+/-),
What is the characteristic lesion of trichorrhexis nodosa?
small nodules along the hair shafts; multifocal or generalized hypotrichosis due to breakage of hair shaft at the nodes
How sensitive is the ACTH stimulation test for diagnosing PPID?
70-79%, best to combine with endogenous ACTH concentrations
What age of horse is typically affected by genital papillomas/papillomatosis? Clinical presentation?
16-18 years of age smooth-surfaced, single or confluent grayish papules/nodules/plaques, keratinized horns
What cell types does a Bacillus Calmette-Guerin (BCG) injection stimulate? For what condition is it used? Most common side effects?
-lymphocytes and natural-killer cells -sarcoids -anaphylaxis
T/F: BPV can replicated and form virions in the horse.
False - viral genomes have been detected but not intact virions
What is XXterra? What is it used for?
ointment containing zinc chloride & extract from bloodroot (Sanguineria canadensis) – rich in alkaloids (sanguinarine, chelerythrine, protopine) -used for treatment of sarcoids -alkalids & zinc chloride have escharotic & caustic properties -sanguinarine has been shown to induce apoptosis, inhibit angiogenesis, & cause cell necrosis
Onchocerca spp. found in North America, Africa, Australia and Europe?
Where are adult worms found?
Where are microfilaria found?
What are vectors?
- Onchocerca gutturosa
- Lamellar part of ligamentum nucae
- Microfilariae – dermis of face, neck, back, and ventral midline
- Vectors – Simulium spp. and Culicoides spp.
Culicoides cross reacts with what other insect?
Simulium (black flies)
T/F: Folliculitis and furunculosis in the horse are extremely pruritic.
False - folliculitis is usually asymptomatic, furunculosis is usually painful
Sarcoptes scabei
Fibroblastic sarcoids clinical presentation (Type 1? Type 2?)
fleshy, ulcerated masses Type 1 - pedunculated Type 2 - broad, locally invasive base
What are therapeutic options for treatment of PPID?
pergolide, cyproheptadine, trilostae; **pergolide (dopamine agonist) is drug of choice
Which cytokine(s) is/are increased in the horse during the summer?
IL-4
Cymopterus watsonii
spring parsley – cause of primary photosensitization (due to fagopyrin)
Fagopyrum spp. Are what type of plant?
buckwheat
What is the classic distribution of Culicoides hypersensitivity?
dorsal - face, mane, withers, rump, and tail -some ventrally feeding spp. - intermandibular space & ventral body wall
T/F: Dermatophilosis is a contagious disease.
True - crusts are the major source of zoospores
What species are hard ticks? Where do they lay eggs? What part of life cycle is spent on the host?
- Dermacentor albipictus
- Amblyomma americanum
- lay eggs in sheltered spots
- adults infest host
What are treatment options for Culicoides hypersensitivity?
- removal of manure & decaying vegetation
- body suit
- repeated application of fly spray/pour-ons
- stable from dusk to dawn (when insects usually feed)
What are the early genes associated with papillomavirus? What do they do?
E5, E6, E7; stimulate cellular proliferation and are responsible for the maintenance and replication of the viral genome within the dividing cell – downregulate mammalian suppressor gene localization, affect trafficking and modification of cellular proteins and cause cytoskeleton disruption
What time of year are the clinical signs of cutaneous onchocerciasis more severe?
warm weather – microfilaria are present in the superficial dermis during warm weather
insect vectors may exacerbate the condition in warm weather
Are the concentrations of dopamine and its metabolites increased or decreased in PPID?
decreased
Why do Icelandic ponies not develop Culicoides hypersensitivity?
No culicoides gnats in Iceland
Which cytokine(s) is/are protective against insect hypersensitivity?
IL-10, TGF-beta
T/F: Any type of sarcoid lesion can develop into an aggressive fibroblastic or malignant/malevolent tumor if traumatized.
True
T/F: Animals with Waardenburg-Klein syndrome have normal melanocytes but cannot synthesize melanin.
False - have no melanocytes; defect in migration & differentiation of melanoblasts
T/F: Dopamine normally inhibits secretion of POMC-derived peptides.
True – so in PPID where dopamine is decreased, these POMC-derived peptides are INCREASED
Most common sites to be affected by classical viral papillomatosis?
muzzle & lips -also eyelids, paragenital regions, distal legs
Albinism is caused by a deficiency in what enzyme?
tyrosinase – have normal melanocytes but cannot make pigment
T/F: Ivermectin and Moxidectin will kill adult Onchocerca worms in addition to the microfilaria.
False – none of the microfilaricides are known to kill Onchocerca worms
Most common sites to be affected by genital papillomas/papillomatosis?
mucosa and skin of the external genitalia -free portion of penis & glans penis -vulval lips, vestibular walls & clitoris in females
DDX for verrucous sarcoids
papillomas or hamartomas
Thamnosma texaria
Dutchman breeches - cause of primary photosensitization (due to furocoumarins)
What papillomavirus(es) are responsible for aural plaques?
EcPV3 and EcPV6 (Genus = Dyorho) EcPV4 and EcPV5 (Genus = Dyoiota)
With telogen defluxion, is the surface of the skin smooth or rough?
Smooth
T/F: Microfilaria of Onchocerca cervicalis can be found in the skin of normal horses.
True
Cause of hemorrhagic nodules in Eastern Europe and Great Britain during spring and summer?
Parafilaria multipapillosa
adult worms live in SQ and intermuscular connective tissue, nodules open to surface and discharge a bloody exudate => larvae & eggs
What is the clinical presentation of selenium toxicosis?
hoof abnormalities, progressive loss of the long hairs of mane, tail & fetlocks
Habronemiasis of the skin is caused by which stage of which nematodes?
third-stage larvae of Habronema muscae, Habronema majus, and Draschia megastoma -adult worms live in stomach & skin lesions are caused by aberrant migration of larvae (larvae are transmitted by flies)
What papillomavirus(es) are responsible for classical papillomatosis?
EcPV1 (Genus = Zeta)
Changes on routine bloodwork suggestive of PPID
hyperglycemia (due to insulin resistance), stress leukogram (neutrophilia, lymphopenia and eosinophenia), elevated insulin, low T4 and T3, mild anemia
T/F: Papillomaviruses can infect intact epithelium.
False - penetrate squamous or mucosal epithelium via trauma
What areas are typically affected by alopecia areata?
mane, tail & face (most common) neck & trunk
T/F: Hypothyroidism is a common cause of alopecia in the horse.
False
Preferred feeding site of Haematobia spp.
Horn fly
- Ventrum on sunny, warm (>22 degrees celsius)
- Topline is favored in rainy or cool weather
Anaerobic non-acid-fast gram-positive bacterium typically an opportunistic bacteria
Dermatophilus congolensis
T/F: Measuring basal thyroid hormone levels is a reliable screening test for hypothyroidism.
False – many things can affect basal T4 and T3 levels in the horse– euthyroid sick syndrome, medications, weather (low in normal horses during warm weather, higher in cold weather); lower in horses doing strenuous exercise; higher in neonates; lower in fasted animals
C. pseudotuberculosis is believed to be spread via what mechanism?
biting flies: Haematobia irritans (horn fly), Stomoxys calcitrans (stable fly), Musca domestica (horse fly) -ticks can also harbor the organism
Treatment of warbles
Caused by Hypoderma bovis or lineatum
- enlarge breathing pore, extract grub
- surgically excise nodule
- routine deworming with ivermectin or moxidectin to preven larval migration and development
Where do soft ticks lay their eggs? What part of life cycle is spent on the host?
- Otobius megnini & Ornithodorus spp. - sheltered spots
- Larvae and nymphs suck blood & drop off of host to become adults
Stomoxys calcitrans = ?
stable fly
Side effects of topical application of imiquimod?
pain, erythema, exudation, erosion at application site
Purpura hemorrhagica is most commonly associated with what infectious agent?
Streptococcus equi (usually from respiratory tract)
Causes of primary photosensitization
plants, mycotoxins, drugs/chemicals
What drugs are known primary photosensitizing agents?
thiazides, sulfonamides, tetracyclines, furosemide, promazines
Ddx for gyrate urticaria
erythema multiforme
Primary photosensitization
preformed or metabolically derived photodynamic agent reaches the skin by ingestion, injection, or contact
Onchocerca spp. seen in Europe and Asia?
Where is the adult worm found?
Vectors?
- Onchocerca reticulata
- Found in connective tissue of flexor tendons and suspensory ligaments of fetlock (esp. front legs)
- Culicoides spp. gnats are intermediate host
T/F: Mast cell tumors in horses are very aggressive.
False - typically grow slowly, lesions may spontaneously resolve, surgical excision is curative
What are the intermediate hosts for Habronemiasis (Habronema muscae, H. majus, Draschia megastoma)?
- Habronema muscae & Draschia megastoma: Musca domestica (housefly)
- Habronema majus: Stomoxys calcitrans (stable fly)
What do chewing lice feed on?
exfoliated epithelium and cutaneous debris
Toxic-shocklike syndrome is caused by toxins of what bacteria?
Staph. aureus (toxic shock syndrome toxin-1)
With telogen defluxion, when does hair loss occur relative to the injury/insult?
After 1-3 months of the insult; injury causes abrupt, premature cessation of growth of anagen hair follicles, which then enter catagen and telogen at the same time
How is a diagnosis of alopecia areata made?
history, physical exam (hairloss without scale and crust), trichogram (dysplastic hairs, exclamation point – short, stubby hairs with frayed, fractured, pigmented distal ends whose shaft undulate or taper toward the proximal end); histopathology
Most common cutaneous vasculitis
purpura hemorrhagica (d/t Strep equi)
What is conventional urticaria?
characterized by papules and wheals that vary from 2 mm to 5 cm
What is the best proven treatment for aural plaques? Side effects?
Topical application of imiquimod (twice weekly, every other week) Typically requires sedation as can be painful - side effects were erythema, edema, erosion, ulceration, exudation & crust formation
Tabanus spp. = ?
Horse fly
Clinical signs of sarcoidosis
scaling/crusting/alopecia on face, trunk or legs => progresses to multifocal/generalized exfoliative dermatitis, lung involvement => exercise intolerance, weight loss, poor appetite
T/F: Naturally occuring zinc deficiency has not been reported in the horse.
True
Intermediate host of Dracunculus medinensis (guinea worm) or Dracunculus insignis?
Aquatic crustaceans (Cyclops spp.) – infection occurs when contaminated water is ingested
What is targeted in alopecia areata?
IgG autoantibodies directed against trichohylain, inner root sheath, outer root sheath, and precortex of the hair follicle
Histopathological echaracteristics of alopecia areata
peribulbar accumulation of lymphocytes – infiltrate the hair bulb, root sheath of inferior segment, infundibulum of hair follicle, apoptotic keratinocytes; chronic changes - predominance of telogen and catagen hair follicles, peribulbar melanosis, follicular atrophy, follicular dysplasia, orphaned sebaceous and epitrichial sweat glands, miniaturized hair follicles
Gram-positive, partially acid-fast, filamentous bacteria that are environmental saprophytes
Nocardia spp.
Why is imiquimod useful for sarcoids?
has antiviral and antitumoral activity -stimulates both the innate and acquired immune system via toll-like receptor 7 => induces a Th1 cytokine response (IL-2, IL-12, IFN-alpha & -gamma), increases TNF-alpha, IL-1, IL-6, IL-8
Where are Culicoides eggs laid?
damp, marshy areas
decaying vegetation
manure
What are the best ways to reduce the incidence of habronemiasis?
- Fly control (requires intermediate fly host)
- Removal of manure and soiled bedding
- Deworming with ivermectin and moxidectin to eliminate adult Habronema and Draschia nematodes from the stomach.
What species of Psoroptes mites parasitize the horse?
P. equi, P. natalensis, P. ovis, P. cuniculi
no host specificity
How is a diagnosis of Pelodera dermatitis made?
Deep skin scraping – can see the nematode larvae (~600 um)
What is relative size of Psoroptes spp. mites? What do they feed on? How long is life cycle?
- Large (0.4-0.8 mm)
- Nonburrowing, feed on tissue fluids
- Life cycle completed on host in 10 days
Peribulbar accumulation of lymphocytes and lymphocytes infiltrating the hair bulb and root sheath are histopathologic findings of what disease?
Alopecia areata peribulbar accumulation of lymphocytes = “swarm of bees” also can see apoptotic keratinocytes with attached lymphocytes (satellitosis)
T/F: Eosinophilic granulomas are painful and pruritic.
False
T/F: Aural plaques require aggressive treatment to prevent transformation to SCC.
False - are usually asymptomatic and do not progress (unlike genital papillomas)
After ingesting plants containing high levels of selenium, when do clinical signs appear?
3 weeks to 3 months
T/F: In the United States, equine sarcoptic mange has been eradicated.
True: is a reportable disease
How is a dexamethasone suppression test different in horses than dogs?
use an overnight dex suppression test– measure cortisol before and 19-24 hours post dex administration; normal horses should suppress, horses with PPID do not
DDX for nodular sarcoids
infectious, reactive inflammatory lesions (eosinophilic granuloma, foreign body) or other neoplasia
What time of year is best to do diagnostic testing for PPID in the northern hemisphere?
before June or after October; concentrations of ACTH and alpha-MSH increase in the fall
The high affinity IgE receptor (FceRI) is present on what cells?
mast cells, basophils, Langerhans cells
With anagen defluxion when does hair loss occur relative to the injury/insult?
Suddenly at time of insult – due to abnormalities of the hair follicle and hair shaft
What Staph species is implicated in pastern dermatitis in horses?
Staph. hyicus (coagulase-variable species, commonly causes exudative dermatitis in pigs)
Histopathology characteristics of sarcoids
-fibroblasts (spindle cells) arranged in bundles w/ oval nuclei and small nucleoli -mitotic figures present in low numbers -fibroblasts & collagen fibers have a whorled/tangled/crisscross/linear/mixed pattern *fibroblasts at the dermoepidermal junction can be arranged perpendicular to the BM (picket-fence pattern)* -neoplastic cells present beneath BM & extend downwards -hyperplastic epidermis with deep rete ridges (50% of cases)
What are the two most important factors in the initiation and development of dermatophilosis?
skin damage & moisture
Other than cutaneous lesions, where else can the microfilaria of Onchocerca cervicalis cause clinical disease?
Eyes
- keratitis, uveitis, peripapillary choroidal sclerosis, vitiligo of bulbar conjunctiva
Photosensitivity
skin has increased susceptibility to damaging effects of UVL because of the production, ingestion, and injection of or contact with a photodynamic agent
What papillomavirus(es) are responsible for genital papillomas/papillomatosis?
EcPV2 (Genus = Dyoiota), EcPV7 (Genus = Dyorho)
Ddx for Conventional and giant urticaria
vasculitis
T/F: Dermatophilus congolensis is a primary pathogen.
False - opportunistic pathogen, causes disease secondary to factors that affect the skin integrity and/or immune response (skin damage, allergies, Cushing’s disease, etc.)
What cell type is characteristic of sarcoids?
fibroblasts
Describe the life cycle of Simulium spp.
- eggs laid on stones/plants below surface of **running water**
- eggs hatch in 6-12 days
- adults live 2-3 weeks
- most active in spring and early summer
Where do (Oxyuris equi) pin worms infest?
cecum and colon –> adult female worms crawl out of the anus and lay eggs in clusters on the perineal skin
What is unusual about the life cycle of Dermatophilus congolensis?
has 2 forms – hyphae and zoospores
How much of daily protein requirements is used for skin and hair growth?
25-30%
Describe the life cycle of Musca autumnalis.
Face fly
- lay its eggs on freshly deposited cow manure
- life cycle is temperature-dependent (varies from 7-14 days)
What species of horn fly causes ventral midline dermatitis in the US?
Haematobia irritans
What age of horse is typically affected by classical viral papillomatosis? Clinical presentation?
horses less than 3 years papules (1mm) with gray to white color => increase in size and can develop frond-like projections
DDX for occult sarcoids
bacterial folliculitis, dermatophytosis, alopecia areata
Treatment for selenosis?
Eliminate source of selenium, addition of inorganic arsenic or salt supplements, naphthalene
Trombiculiasis larvae are what size? How long is life cycle? What species are found where?
- Larvae are 0.2-0.4 mm in length and vary from red/orange/yellow
- Trombicula alfreddugesi & T. splendens - forested & swampy areas (north and south America)
- Trombicula autumnalis (harvest mite) - Europe & Australia
- T. sarcina - Australia (leg itch mite/blacksoil itch mite)
- Feeds for 7-10 days, then drops off of the host to molt. Life cycle is 50-70 days in entirety