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
What can cause 1-2 mm wide grayish-white, crooked streaks in the skin of teh cheeks, neck and shoulders but does not usually cause pruritus?
Gasterophilus spp. larvae that penetrate facial skin and oral mucosa
What breed is predisposed to lethal white foal syndrome?
paints (specifically overo)
How is a diagnosis of purpura hemorrhagica made?
clinical signs; ELISA test for antistreptococcal antibody titer; biopsy
What is the infectious stage of Dermatophilus congolensis?
zoospores (created from coccoid cells that break off the filamentous hyphae)
With anagen defluxion, is the surface of the skin smooth or rough?
stubbled hairs are felt - hairs are breaking off abnormally
DDX for sarcoids on histopath
Schwannomas (nerve sheath tumor) – differentiate based on IHC (schwannomas have S-100 protein which sarcoids lack)
T/F: Iatrogenic hyperadrenocorticism is common in the horse.
False – has not been reported
T/F: Infestation with Cochliomyia hominivorax is a common problem in the US.
False: reportable disease!
What breed is predisposed to Equine Multisystemic Eosinophilic Epitheliotropic Disease?
standardbreds
Musca autumnalis = ?
Face fly
Histopathological changes with eosinophilic granulomas
collagen flame figures; nodular to diffuse areas of eosinophilic granulomatous inflammation of dermis +/- panniculus; older lesions may have dystrophic mineralization
Factors that lead to SCC
UV light exposure, chronic inflammation, equine papillomavirus-2
Where are the adult worms of Onchocerca cervicalis located?
- funicular portion of ligamentum nuchae
Exotoxin Phospholipase D - associated with what bacteria? characteristics of the toxin?
C. pseudotuberculosis -hydrolyzes epithelium => increases vascular permeability => edema -inhibits neutrophil chemotaxis & degranulation of phagocytic cells
Most common dermatophytes in the horse
Trichophyton equinum or Microsporum canis (microsporum equinum is an equine-adapted M canis)
Where are the cutaneous lesions associated with Onchocerca most common?
ventral midline (especially umbilicus)
face & neck
Lolium perenne
perennial rye grass – cause of primary photosensitization (due to perloline)
Twisted or misshapen and irregular hair shafts is suggestive of what underlying condition?
nutritional disorder
What are the three features required for photosensitization to occur?
1) Presence of a photodynamic agent within the skin, 2) Exposure to a sufficient amount of certain wavelengths of UVL, 3) Cutaneous absorption of UVL (facilitated by lack of pigment and hair coat)
What factors are associated with an increased prevalence of insect-bite hypersensitivity?
1) breed (Friesian, Shetland pony); 2) age (starts at <4 yrs); 3) region (near wooded areas, higher temps and minimal winds); 4) type of bedding (wood shavings vs. other beddings)
How is a diagnosis of Habronemiasis made?
- deep scrapings or smears from lesions may reveal nematode larvae + eosinophils + mast cells
- biopsy - dermatitis with eos + mast cells
- **Mutifocal areas of discrete coagulation necrosis with nematode larvae
- PCR can detect
What is the most common Staph species found in horses?
Staph. aureus
Phytoalexins
phototoxic agent in fungus on celery and parsnips
T/F: Poor genital hygiene may predispose to squamous cell carcinoma.
True
Most tick species found on horses in the US require how many hosts?
three - require a different host for every instar, drop off host each time after engorging, molt on the ground
Phototoxicity
classic sunburn reaction, dose-related response to light exposure
T/F: Every animal infested with Onchocerca cervicalis will develop clinical signs.
False: thought to represent a hypersensitivity reaction to microfilarial antigens
-exacerbation of cutaneous signs is seen with microfilaricidal therapy
T/F: Fleas are host specific.
False!
Clinical presentation of purpura hemorrhagica
edema in muscle and SQ tissues (predominantly limbs) purpuric lesions in skin and mucous membranes depression, anorexia, fever, epistaxis, weight loss, tachypnea, etc.
Hepatogenous photosensitization
blood phylloerythrin levels are elevated in association with liver abnormalities
What are the most common MRSA isolates in horses?
CMRSA-5 (USA500), SCCmec IV
Most important blowflies in North America
Phormia regina
Phormia terrae-novae
What are the typical histopathologic findings of alopecia areata?
peribulbar inflammation or presence of fibrosis surrounding hair follicles
What drug is the drug of choice for treatment of PPID?
pergolide – dopamine agonist
How soon after a stressful event does alopecia due to telogen effluvium become apparent?
1-3 months
What is unique about the color of viral papillomas?
have reduced or absent melanin pigment (depigmented lesions) - due to alterations in melanogenesis & melanocyte-keratinocyte interaction
Primary lesions of dermatophilosis?
follicular & nonfollicular tufted papules
What is parasite?
Oxyuris equi
What are the proposed mechanisms for the hypertrichosis seen with PPID?
1) Increased adrenocortical production of androgens, 2) Increased secretion of alpha-MSH, 3) Pressure of pituitary lesion on thermoregulatory areas of the hypothalamus
T/F: Lesions of purpura hemorrhagica blanch with diascopy.
False
Actinomyces spp. has what type of granules that can be used for culture?
sulfur granules
Psoroptes mite
What is hypericum perforatum? What changes can it produce in equine skin?
St. John wort; cause of primary photosensitization (due to hypericin)
Describe the life cycle of Tabanids.
- eggs laid near water
- eggs hatch and first-stage larvae move to damp areas
- can hibernate if environmental conditions are unsatisfactory
When is trombiculiasis most common?
late summer and fall, when larvae are active
Sarcoptes scabei
What attracts culicoides to their target?
sight, body temperature, heart sound, smell - CO2, lactic acid, octenol
Treatments for sarcoids
-CO2 laser -cryotherapy -hyperthermia -radiotherapy -chemotherapy (intralesional injections or topical application) -topical antiviral therapy (acyclovir, cidofovir) -BCG vaccination (Mycobacterium bovis) + flunixin/dexamethasone -imiquimod
Clinical signs associated with multisystemic eosinophilic epitheliotropic disease
scaling/crusting/alopecia, fissures on coronets or face, oral ulceration, ulcers on mucocutaneous junctions, weight loss, fever, diarrhea*
T/F: Systemic treatment with an antifungal is the gold standard for dermatophyte infections in horses.
False - can usually be managed topically
What is a unique treatment for pemphigus foliaceus for horses?
injectable gold salts (aurothioglucose or aurothiomalate)
Deep skin scrapes are useful to find which parasite(s)?
Demodex equi & Rhabditis strongyloides
Chrysops spp. = ?
Deer flies
T/F: Urticaria can be caused by cold and exercise.
True
What do sucking lice feed on?
blood and tissue fluid
Epidermal changes seen on histopathology from papillomaviruses?
-compact orthokeratosis & parakeratosis -papillary epidermal hyperplasia with acanthosis -lack of melanin pigment -basal cells have increased mitotic index -viral inclusions (intranuclear, basophilic) seen in spinous & granular layers
Occult sarcoids clinical presentation
focal areas of alopecia, scaling, skin thickening, hyperkeratosis, & hyperpigmentation
Describe the life cycle of the stable fly.
- eggs laid in wet straw, bedding or manure
- life cycle is temperature-dependent but usually about 4 weeks in warm weather
What is spectrum of UV light responsible for photosensitivity reactions?
UVA
T/F: Genital papillomas/papillomatosis can progress to invasive squamous cell carcinomas.
True
Which species of Onchocerca may be nonpathogenic in the horse?
Onchocerca gutturosa
What organ systems may be affected by sarcoidosis?
skin, lung, mesenteric/thoracic lymph nodes, liver, GI tract, spleen, kidney, bone, CNS, heart, adrenal glands, thyroid glands, thymus, skeletal muscle, bone marrow
T/F: Microfilaria of Onchocerca cervicalis are commonly found in peripheral blood of affected animals.
False - rarely found
Histopathology findings from Dermatophilus congolensis?
thick crust composed of palisading layers of parakeratotic stratum corneum, dried serum, degenerating neutrophils with Gram stain – can see the branching, filamentous organisms in the crusts and follicles
T/F: Systemic glucocorticoids are effective as the sole systemic agent for equine habronemiasis.
True
Haematopota spp. = ?
Horse flies
Treatment of cutaneous onchocerciasis. What precautions need to be taken?
- Thorough ocular examination prior to therapy
- Systemic glucocorticoid administration for the first 5 days of microfilaricidal treatment (destruction of microfilariae can exacerbate skin and ocular lesions)
- Microfilaricidal treatment with either Ivermectin or Moxidectin will kill the microfilaria within 14 days – a second treatment is rarely needed.
Most common location for lesions due to Habronema spp.?
- legs, ventrum, prepuce, urethral process of the penis, medial canthus of the eyes, conjunctiva, commissures of the lips, wounds
What are virulence factors of Strep. equi equi?
-M(SeM) protein: inhibits phagocytosis, complement deposition -hyaluronic acid capsule
Gram-positive, facultative intracellular, pleomorphic pathogen that survives and replicates in phagocytes. Causes abscesses, folliculitis, furunculosis, and ulcerative lymphangitis in horses
Corynebacterium pseudotuberculosis
Treatment for Chorioptic mange
- Clip feathers of draft horses
- Topical treatment with 2% selenium sulfide shampoo, 2% lime sulfur, 0.25% fipronil spray
- Clean barn thoroughly!
T/F: Genital papilloma lesions may be asymptomatic.
True - may be asymptomatic until extensive – need good routine examination of external genitalia
What is the most common ddx with papular urticaria?
stinging insects (esp mosquitoes)
Infectious agents involved in the pathogenesis of equine sarcoids?
Bovine papillomavirus (BPV) types 1 & 2
Any horse older than 7 years that develops an unexplained laminitis should be test for what?
PPID
What are natural barriers to UVL?
stratum corneum, melanin, blood, carotenes
T/F: The urticarial lesions of erythema multiforme pit with digital pressure.
False (unlike true urticaria)
Culicoides hypersensitivity is what type of hypersensitivity reaction? To what antigen?
Type I (immediate & late phase) and type IV (delayed) hypersensitivity to salivary antigens
T/F: Animals with vasculitis will usually have a positive ANA.
False – infrequently will be positive
Examples of screw-worms
- Cochliomyia hominivorax
- Cochliomyia macellaria
Describe the life cycle of Haematobia spp.
Horn fly
- Eggs laid in fresh cow manure *** (eggs laid in horse manure will NOT develop)
- 10-14 day life cycle
Waardenburg-Klein syndrome has been described in what breed?
paints
T/F: Oxyuriasis is primarily seen in pastured animals.
False: more common in stabled animals
Piedra is caused by what organism?
Trichosporon beigelii
T/F: Both vitamin A deficiency and excess can cause a rough, dull hair coat, alopecia, scaling and hyperkeratosis.
True
T/F: Psoroptes causes pruritus.
True - dermatitis and/or otitis externa
Where are the most common areas for lesions of erythema multiforme? What do they look like?
neck and dorsum; annular, arciform, serpiginous, “donut” and polycyclic shapes; do not pit with digital pressure
What layer(s) of the epidermis are affected by papillomaviruses?
-basal keratinocytes - virus is latent in these cells -stratum spinosum & granulosum (as the cells divide)
Gram-positive, filamentous anaerobic bacteria that are opportunistic invaders of damaged oral mucosa and skin
Actinomyces spp.
What species of Onchocerca is seen in North America?
Onchocerca cervicalis
Culicoides gnats are vectors for what pathogens?
Onchocerca cervicalis
Why are multiple baths needed to clear a lice infestation?
The adults will disappear after the first bath, but the eggs (nits) can persist until after the second bath as they are cemented to the hair shafts
Deficiency in copper can result in what changes in the skin and hair coat?
hair coat fading, leukotrichia (copper is needed for the enzymatic conversion of tyrosine to melanin)
Trombiculiasis - what stage causes dermatitis in the horse?
- Larvae/nymphs
Haematobia (Lyperosia) spp. = ?
horn flies
What species of tick cause otitis externa?
Otobius megnini (spinose ear tick)
what species of flea can affect the horse?
Ctenocephalides felis felis
Tunga penetrans
Echidnophaga gallinacea
T/F: Habronema larvae can only penetrate wounds or broken skin.
False: can penetrate intact skin
T/F: Sarcoids are not associated with abnormalities in Ki67 expression or p53 expression.
True
Ammi majus
bishop weed - cause of primary photosensitization (due to furocoumarins)
Treatment for eosinophilic granulomas
surgical excision, sublesional injection of steroids, systemic glucocorticoids, treatment of underlying disease (IBH or AD)
What are the species of Demodex in horses?
- Demodex caballi (larger) - found on eyelids and muzzle
- Demodex equi (smaller) - found on body
Most common causes of urticaria
drug reactions, feedstuffs, atopic dermatitis, infections/infestations
Histopathology characteristics of urticaria
mild to moderate perivascular to interstitial dermatitis with numerous eosinophils and lymphocytes and variable dermal edema; normal epidermis
Treatment for classical viral papillomatosis?
benign neglect - should spontaneously resolve in 1-9 months topical caustic agents: podophyllin, salicylic acid, trifluoroacetic acid mixture, tincture of benzion - apply once every 4 days until remission
What clinical signs are associated with selenosis?
lameness (usually starts in hind end), coronary band area becomes tender, hoof wall deformities – hoof rings, corrugations, horizontal cracks; hair coat is rough – loss of long hairs of mane and tail
T/F: ACTH is normally produced by the pars intermedia.
True – although it is produced by the pars DISTALIS in much greater proportion. However, in PPID, it is overproduced by the pars intermedia due to a lack of dopaminergic inhibition
What breeds appear to be at increased risk of PPID?
ponies and Morgans
What pathogen can Musca autumnalis carry?
eggs or larvae of Habronema spp.
What plants accumulate selenium to a higher level?
Astragalus spp. (Milkvetch), Xylorhiza spp. (woody aster), Gutierrezia spp. (snakeweed), Grindelia spp. (gumweed), Sideranthus spp., Greyia spp., Aster spp., Atriplex spp. Penstemon spp., Casteilleja spp., Oonopsis spp., Stanleya spp.
Main differentials for ventral midline dermatitis
Haematobia irritans, Culicoides spp.
Foals with lethal white foal syndrome have a mutation in the gene for what?
endothelin receptor B – this pathway is critical for proper development and migration of neural crest cells that form melanocytes and enteric neurons
Culicoides can cross react with what other insects?
Simulium spp. (black flies), Stomoxys calcitrans (stable fly), Haematobia irritans (horn fly)
What is the agent present in some plants that can cause hepatogenous photosensitization?
pyrrolizidine alkaloids, nagione, lantadenes, saponins
T/F: Foals do not produce IgE for at least 6-9 months after birth.
True - but maternal IgE can be detected in serum
Clinical presentation of Equine Multisystemic Eosinophilic Epitheliotropic Disease (MEED)?
-alopecia & poor hair coat -weight loss & diarrhea -epistaxis
What breed is predisposed to coat color dilution lethal (lavender foal syndrome)?
Arabians (specifically of Egyptian breeding)
T/F: Lice are highly host-specific and spend their entire life cycle on the host.
True – except poultry lice will feed on horses!
Low affinity IgE receptor is present on what cells?
B-lymphocytes
How is the diagnosis of sarcoids made?
-lesions suggestive of a sarcoid -PCR positive for BPV-1 or BPV-2 DNA (via superficial swabs and scrapings) -biopsy
What age of horse is typically affected by aural plaques? Clinical presentation?
>1 year of age well-demarcated, shiny, erythematous or depigmented lesions covered with a whitish keratinous crust on concave aspect of pinna
Nodular sarcoids - type A & B
Type A - spherical subcutaneous masses Type B - dermal involvement
What abnormalities are present with Waardenburg-Klein syndrome?
blue eyes, amelanotic skin & hair => animals are deaf
How is a diagnosis of habronemiasis made?
lesion location & appearance - limbs, ventral abdomen, external genitalia, ventral canthus of eye; appear as ulcerated masses that may bleed easily cytology - small (<1 mm) yellow granules (may contain larvae) biopsy -eosinophilic inflammation w/ coagulation necrosis (+/- larvae)
Histopathological characteristics of photoactivated vasculitides
leukocytoclastic, necrotizing vasculitis of superficial dermal blood vessels; thrombosis, purpura, epidermis edematous or necrotic
Exposure to UVB and UVC light causes what changes in the skin?
clusters of vacuolated keratinocytes (“sunburn cells”), apoptotic keratinocytes, vascular dilatation and leakage, depletion of Langerhans cells and mast cells, increase in tissue levels of histamine, prostaglandins, leukotrienes and other vasoactive compounds, oxygen intermediates (superoxide radical, hydrogen peroxide, and hydroxyl radical)
Clinical signs with cutaneous onchocerciasis
- **annular lesion in the center of the forehead
- alopecia, scaling, crusting, inflammatory plaques
- +/- pruritus
- +/- ocular signs
Zoospores of D. congolensis are released in what conditions?
-moist environments -low concentrations of Co2 (repelled by high conc. of Co2)
Describe the life cycle of blowflies.
Phormia regina & Phormia terrae-novae
- yellow eggs laid in wounds or carcasses
- larvae pupate in ground, dry parts of a carcass, or long hairs of the tail
Pelodera dermatitis (Rhabditic dermatitis) is caused by infestation of what parasite?
Pelodera (Rhabditis) strongyloides – facultative nematode parasite
lives in moist, filthy environmental conditions (damp soil, decaying organic material)
dermatitis is in areas in contact with the contaminated environment
Verrucous sarcoid clinical presentation
rough, alopecic, raised surface
Malignant/malevolent sarcoids clinical presentation
aggressive & locally invasive; extend widely into adjacent skin & SQ, infiltrate lymphatic vessels
What is the poultry mite that can attack humans and horses? Fowl mite?
- Dermanyssus gallinae =* poultry mite
- Ornithonyssus sylviarum* = fowl mite
What is relative size of Sarcoptes spp. mites? What do they feed on? How long is life cycle?
- Medium (0.25-0.6 mm in diameter)
- Tunnel through epidermis and feed on tissue fluids & epidermal cells
- Life cycle completed on the host in 2-3 weeks
- Susceptible to drying and only survive a few days off of the host
Describe the life cycle of the screw-worm
Cochliomyia hominivorax and Cochliomyia macellaria
- Adults deposit clusters of eggs at the edge of a wound of any size
- Deposit eggs near any natural body opening (nostrils, prepuce)
- **Breed only in wounds and sores on living hosts and NOT carcasses**
- Larvae hatch within 24 hours and burrow into LIVING tissue
- more common in spring, early summer and early fall
What is produced by dermatophytes that damages skin and hairs?
proteases – digest keratin (keratinase)
What stage of Onchocerca causes cutaneous lesions in the horse?
microfilaria
Clinical presentation of Psoroptic mange?
- ear disease: head shaking, ear scratching, head shyness, lop-eared appearance
- truncal dermatitis
- mane and tail disease - seborrhea
T/F: A normal horse may have an elevated ACTH in the fall.
True
Fractured or clearly split hair shafts is indicative of what behavior?
excessive grooming or self-trauma (pruritus)
What is relative size of Chorioptes spp. mites? What do they feed on? How long is life cycle?
- Small (0.3-0.5 mm long)
- Surface-inhabiting parasites that feed on epidermal debris
- Life cycle is 3 weeks completed on host
- Can survive off-host for 70 days
What is the difference between a louse egg on a hair and a Chyletiella egg on a hair?
louse eggs are cemented to hair shafts, Chyletiella is loosely adhered
Clinical presentation of Habronemiasis?
- granulomatous inflammation, ulceration, intermittent hemorrhage, serosanguinous exudate, exuberant granulation
- pruritus
- Small (<1 mm) yellowish granules ***
- dysuria, pollakiuria (when urethral process is involved)
What is immersion foot?
vasoneuropathy associated with prolonged exposure to moisture, cold temperatures and impaired blood flow to extremities
Treatment principles for photoactivated vasculitides
sun avoidance, glucocorticoids, pentoxifylline
What is the chewing lice of horses?
Bovicola (Werneckiella) equi
What treatments have shown efficacy in treating alopecia areata?
none! anecdotal reports of minoxidil and topical tacrolimus
What Streptococcal species have been isolated from horses?
Strep. equi equi Strep. equi zooepidemicus Strep equisimilis
Copper is an essential component of what oxidative enzymes?
tyrosinase, ascorbic acid oxidase, lysyl oxidase, cytochrome oxidase
Simulium spp. AKA ?
Black flies
Histopathological changes with cutaneous onchocerciasis.
- superficial & deep perivascular-to-interstitial dermatitis with numerous eosinophils
- microfilariae in superficial dermis**** surrounded by eosinophils
Why is fly control an important part of treatment regimen for aural plaques?
can worsen the lesions and can mechanically transmit papillomavirus
What are goitrogens?
interfere with iodine uptake by thyroid gland; e.g. thiocyanates, perchlorates, rubidium salts, arsenic
How is a diagnosis of oxyuriasis made?
Demonstration of eggs on perineal skin
Most common cause of ulcerative lymphangitis?
C. pseudotuberculosis (also staph, strep, Actinomyces, etc.)
Special stain to identify equine mast cells
Toludine blue
What species of bacteria causes equine strangles?
Strep. equi equi
T/F: Aural plaques typically regress spontaneously.
False
What type of immune response is necessary to clear a dermatophyte infection?
cell-mediated
Describe the life cycle of Hypoderma bovis and Hypoderma lineatum.
- H. bovis => SINGLE egg laid on a hair Larvae hatch in about 4 days -> penetrate skin -> 1st stage larvae spinal canal and epidural fat (winter) => 2nd stage larvae migrate to SQ (spring) => 3rd stage larvae => penetrate skin
- H. lineatum => 6 or MORE eggs laid on a hair => Larvae hatch in about 4 days -> penetrate skin => 1st stage larvae in submucosal connective tissue of esophagus (winter) => 2nd stage larvae migrate to SQ (spring) => 3rd stage larvae => penetrate skin
In addition to skin and coat changes, what other changes are noted with coat color dilution lethal (lavender foal syndrome)?
neurologic abnormalities – opisthotonus, padling, extensor rigidity, seizures, blindness, unable to assume sternal recumbency
What is the sucking lice of horses?
Haematopinus asini
Specific type of pressure-induced urticaria, wherein wheals conform to a particular configuration reflecting exogenous pressure (e.g. saddle, tack).
Dermatographism
How to control Haematobia spp.
Horn fly
- remove cow manure!
- adult fly rarely leaves the host –> daily application of fly spray controls the infestation
BPV-1 has been detected in what insects?
Musca automnalis, Fannia carnicularis, & Stomoxys calcitrans
Management recommendations for horses with PPID
routine clipping of the hair coat – to decrease heat stress, matting, and risk of infections
T/F: The presence of BPV DNA has been demonstrated up to 16mm outside a visible sarcoid.
True – reason for high recurrence rate
Demodicosis in horses is commonly associated with what conditions?
Chronic treatment with systemic glucocorticoids
PPID
What are the four known species of Chorioptes mite?
Chorioptes bovis, Chorioptes caprae (goats), Chorioptes equi (horses), Chorioptes ovis (sheep)
How many equine papillomaviruses have been isolated?
Seven
T/F: Simulium spp. are strong fliers.
True: can fly over 10 km
DDX for fibroblastic sarcoids
granulation tissue, infectious process (habronemiasis), SCC
Histopathological characteristics of vasculitis
cell-poor hydropic interface dermatitis, mural folliculitis, segmental epidermal necrosis, loss of definition and staining intensity and atrophy or necrosis of hair follicles
