Equine Dermatology - Definitions Flashcards
Habronemiasis “Summer Sores”
Etiology: Habronema muscae, Draschia megastoma, H. majus. CS: granulomas on eyelid, lower leg, ventrum, prepuce. Dx: impression smears (+/- eosinophils), deep skin scrapings, biopsy. Therapy: debulking, reduce inflammaiton, prevent reinfection, avermectins.
Onchocerciasis
Etiology: filarial nematode (Onchocerca cervicalis). Hypersensitivity rxn to dead microfilaria. Lesions: ocular - uveitis, erythema, crusting, scaling, alopecia, depigmentation, lesion in center of forehead, ventral abdominal involvement, pruritis, worse in summer, may scar. Hx: biopsy (submit 1/2 for histo, 1.2 with scalep in saline). Tx: ivermectin or moxidectin.
Warbles
Etiology: Hypoderma bovis, H. lineatum. Aberrant host migration to the back (cattle must be in close proximity to horses). Nodules develop in spring on back. Breathing pore. Tx: removal of grub, routine worming.
Pediculosis
Damalina equi (biting louse), Haematopinus asini (sucking louse). Spp specific. Worse in winter. Dorsal pruritus, dull coat. Dx: flea combing, trichogram. Tx: pyrethrin based topicals, Selsun Blue, 0.25% fipronil. Treat all in contact horses.
Chiggers
Trombicula alfreddugesi, T. splendens. Lesions: papulres and wheals with orange dot in center. Dx: scrapings. Tx: self limiting, lime sulfur, fipronil, permithrin.
Sarcoptic Mange
Sarcoptes scabiei. Pruritis with papules crust, alopecia. Starts on head. Zoonotic. Reportable. Tx: let state vets do it.
Psoroptic Mange
Psorptes equi, P. cuniculi. Lesions on mane, tail or ears. Highly pruritic. Not zoonotic or reportable. Easy to find on body. Tx: ivermectin.
Chorioptic Mange
Leg mange. Chorioptes equi. Most common. Affects lower legs and pasterns esp draft. Pruritis. Not zoonotic or reportable. Tx: ivermectin.
Demodectic Mange
Demodex equi, D. caballi. Very rare. Alopecia and scale on the head/dorsum. Immunocompromised. Dx: deep skin scrape.
Dermatophilosis
Rain rot, rain scald. Dermatophilus congolensis. Source: soil, carriers. Path: spores released when wet and invade skin in areas of trauma. Spread by flies, fomites, etc. Lesions: crusting dermatitis, dorsal, muzzle, legs. Matted hair. Dx: cytology, biopsy. Remove crusts: may be painful, can stay infectious for long time. Eliminate fomites. Topicals: iodophors, lime sulfur, chlorhexidine.
Staphylococcal Folliculitis
Summer scab/saddle scab. S. aurus. Papules, pustules, crusts, scales. Spring/summer, saddle and tack areas. Dx: cytology from pustule/papule, neutrophils. Tx: mild = topicas, severe = topicals and systemic antibiotics - TMS, enrofloxacin.
Papillomatosis
Warts. Two types: lesions on muzzle/lips +/- distal extremities; lesions on concave surface of pinnae. Muzzle/lip lesions - young horses, resolve within 3 mo. Solid immunity - does not recur. Aural plaques - any age, black flies as vector, do not resolve, cosmetic problem.
Equine Sarcoid
Most common skin neoplasm. Viral induced - BPV 1 and 2 in sarcoids via PCR, flies may be involved in spread. Familial predisposition. Rare in horses younger than 1 year old. Four types: verrucous, fibroblastic, mixed, occult. Occur: head, lower leg, prepuce. Dx: signs, biopsy. Tx: wide surgical excision, 50% recur, radiation, cryotherapy, CO2 laser, BCG immunostimulation, intralesional cisplatin, 5 FU.
Pythiosis
Swamp Fever. “FL horse leeches’. Pythium insidiosum. Zoospore swims towards damaged animal or plant tissue and encysts. Areas in contact with water - legs, ventrum. Ulcerated granulomas with draining tracts, yellow/gray necrotic gritty plugs, severe pruritys, may encircle limb. DDx: infectious granulomas, habronemiasis (proud flesh), fibroblastic sarcoids, exuberant granulation tissue. Dx: cytology, biopsy, cutlure , PCR. Tx: early, radical surgical excision, Ampotericin B, cryosurgery, immunotherapy. Poor prognosis.
Dermatophytosis
Most common: Trichophyton equinum. Lesions: scales, crusts, alopecia, head, neck, girth, thorax, usually non-pruritic. Early lesions resemble hives. Uncommonly zoonotic. Dx: fungal culture, trichogram, biopsy (PAS). Tx: Topicals - 2% lime sulfur, enilconazole, miconazole/chlorhexidine, bleach. Mostly self limiting.
Pastern Dermatitis
Grease Heel Complex. Dermatophilosis, dermatophytosis, staphylococcus, chorioptes, chiggers, contact derm, photoactivated vasculitis.
Culicoides
Lay eggs in still water (marshes), decaying vegetation, manure. Ventral midling, topline lesions. Hypersensitivity: seasonal pruritis, genetic predispositions (Iceland ponies, German shires, Arabians, Connemaras, quarterhorses). Pruritus, papules, wheals, excoriation, alopecia, scaling, crusting, rat tail, short mane. Dx: IAD testing. Tx: Avoidance, insect repellent (pyrethrins, permethrin), antihistimines, corticosteroids, fatty acids, topicals, immunotherapy.
