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.
