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Large and Farm Animal Sampler Chapter 5: Bacterial Skin Diseases From Color Atlas of Farm Animal Dermatology, Second Edition. by Danny W. Scott. Chapter 3: Husbandry and Health Planning to Prepare for Lambing or Kidding: Ensuring Pregnancy in Ewes and Does From Practical Lambing and Lamb Care – A Veterinary Guide, Fourth Edition. by Neil Sargison, James Patrick Crilly, and Andrew Hopker. Chapter 4: Head and Neck Surgery From Bovine Surgery and Lameness, Third Edition. by A. David Weaver, Owen Atkinson, Guy St. Jean, and Adrian Steiner. and Brendan Carmel. 295 5.1 Bacterial Skin Diseases Folliculitis and Furunculosis Corynebacterium pseudotuberculosis Infection Dermatophilosis Pododermatitis Miscellaneous Bacterial Diseases Abscess Bacterial Pseudomycetoma Opportunistic Mycobacterial Infection Actinobacillosis Nocardiosis Clostridial Cellulitis Necrobacillosis Folliculitis and Furunculosis Figure 5.1-1 Bacterial folliculitis. Erythema, papules, and crusts in Features the ventral abdominal area. Folliculitis (hair follicle inflammation) and furunculosis (hair follicle rupture) are common and cosmopolitan. Cultural evaluations have not been reported, but anec- dotal literature suggests that Staphylococcus aureus and S. intermedius are causative. Predisposing factors include trauma (e.g., environmental, insect/arachnid) and moisture. There are no apparent breed, sex, or age predilections. Lesions can be seen anywhere, most commonly over the muzzle, back, ventrum, and distal hind legs (Figs. 5.1‐1 to 5.1‐5). Lesion location is often indicative of inciting cause(s). Lesions consist of erythematous papules, pustules, brown‐to‐yellow crusts, epidermal collarettes, and annular areas of alopecia and scaling. Pruritus is typically only seen when inciting causes include insects and arachnids. Furuncles are character- ized by nodules, draining tracts, ulcers, and variable pain. Affected animals are usually otherwise healthy. Pending the inciting cause(s), single or multiple animals Figure 5.1-2 Bacterial folliculitis with intertrigo. Perivulvar may be affected. hyperpigmentation and ulceration. Color Atlas of Farm Animal Dermatology, Second Edition. Danny W. Scott. © 2018 John Wiley & Sons, Inc. Published 2018 by John Wiley & Sons, Inc. 296 Section 5: Camelid Figure 5.1-5 Bacterial folliculitis. Swelling and crusts on lower eyelid. Figure 5.1-3 Bacterial folliculitis. Multiple annular areas of alopecia and crusts over the rump. Figure 5.1-6 Bacterial folliculitis. Direct smear (Diff‐Quik stain). Degenerate neutrophils and large numbers of extra‐ and intracellular cocci (arrow). Diagnosis 1) Microscopy (direct smears): Suppurative inflammation with degenerate neutrophils, nuclear streaming, and Figure 5.1-4 Bacterial folliculitis. Annular area of alopecia crust phagocytosed cocci (Gram‐positive, about 1 µm and scale on rump. diameter, often in doubles or clusters) with folliculitis (Fig. 5.1‐6). Furunculosis is characterized by pyogran- Differential Diagnosis ulomatous inflammation. 2) Culture (aerobic). Dermatophilosis, dermatophytosis, demodicosis, sterile 3) Dermatohistopathology: Suppurative luminal follicu- eosinophilic folliculitis and furunculosis, and zinc‐ litis with degenerate neutrophils and intracellular responsive dermatitis. cocci; pyogranulomatous furunculosis. Bacterial Skin Diseases 297 Corynebacterium Pseudotuberculosis phic bacteria (coccoid, club, and rod forms) that may Infection be arranged in single cells, palisades of parallel cells, or annular clusters resembling “Chinese letters”; bacteria Features usually few in number. 2) Culture (aerobic). C. pseudotuberculosis infection is uncommon and 3) Dermatohistopathology: Nodular to diffuse pyogran- cosmopolitan. The organism contaminates various ulomatous dermatitis and panniculitis. Intracellular wounds, and moisture and flies are important contribut- Gram‐positive bacteria not commonly seen. ing factors. There are no apparent age, breed, or sex predispositions. Lesions are solitary or multiple subcutaneous nodules Dermatophilosis or abscesses. The head, submandibular, and cervical regions are most commonly affected (Fig. 5.1‐7). Features Dermatophilosis (“streptothricosis,” “rain rot,” and “rain Differential Diagnosis scald”) is a rare, cosmopolitan skin disease. Dermatophilus Other bacterial (e.g., Trueperella pyogenes, Burkholderia congolensis proliferates under the influence of moisture pseudomallei) and fungal infections. (especially rain) and skin damage (especially ticks, insects, and prickly vegetation). The disease is more common and more severe in tropical and subtropical Diagnosis climates and outdoor animals. There are no apparent 1) Microscopy (direct smears): Pyogranulomatous age, breed, or sex predilections. inflammation. Intracellular Gram‐positive pleomor- Lesions can be anywhere, but frequently present as exudation, matted hairs, thick crusts, and hair loss on the pinnae, dorsum, and distal legs (Fig. 5.1‐8). Lesion loca- tion may be indicative of inciting cause(s). The condition is typically neither pruritic nor painful. Multiple animals may be affected. Dermatophilosis is a zoonosis. Human skin infections are rare and characterized by pruritic or painful lesions in contact areas (especially arms). Figure 5.1-7 Abscess. Abscess below mandible. Figure 5.1-8 Dermatophilosis. Crusts on dorsum. 298 Section 5: Camelid Differential Diagnosis Bacterial folliculitis, dermatophytosis, demodicosis, and zinc‐responsive dermatitis. Diagnosis 1) Microscopy (direct smears): Suppurative inflammation with degenerate neutrophils, nuclear streaming, and Gram‐positive cocci (about 1.5 µm diameter) in 2 to 8 parallel rows forming branching filaments (“railroad tracks”) (Fig. 5.1‐9). 2) Culture (aerobic, difficult). 3) Dermatohistopathology: Suppurative luminal follicu- litis and epidermitis with palisading crusts containing Gram‐positive cocci in branching filaments. 4) Polymerase chain reaction (PCR) (culture, animal samples). Pododermatitis Features Pododermatitis is a multifactorial disorder seen in alpacas and llamas. Recognized causes include trauma, bacterial folliculitis (see this chapter), yeast infection (see Chapter 5.2), chorioptic mange (see Chapter 5.3), sarcoptic mange (Chapter 5.3), contact dermatitis (see Chapter 5.7), insect‐bite hypersensitivity (see Chapter 5.5), Figure 5.1-10 Pododermatitis. Interdigital skin is thickened and and zinc‐responsive dermatitis (see Chapter 5.8). Deep hyperpigmented with crusts and ulcers (cytology positive for infections are associated with Staphylococcus spp., cocci and rods). Trueperella spp., and Fusobacterium spp. Lesions are usually seen on the interdigital skin of one or multiple feet. Superficial inflammation is characterized by erythema, scales, crusts, and variable hyperpigmen- tation, lichenification, exudation, and waxy accumulations. Deep inflammation is characterized by ulcers and draining tracts (Figs. 5.1‐10 and 5.1‐11). Pruritus, pain, and lameness are variable findings. Differential Diagnosis Chorioptic mange, yeast dermatitis, sarcoptic mange, contact dermatitis, insect‐bite hypersensitivity, and zinc‐ responsive dermatitis. Diagnosis Pending the historical and clinical findings, diagnostic tests could include: 1) Cytology 2) Culture Figure 5.1-9 Dermatophilosis. Direct smear (Diff‐Quik stain). 3) Skin scrapings Branching filaments composed of cocci (“railroad tracks”) (arrow). 4) Biopsies. Bacterial Skin Diseases 299 Figure 5.1-11 Pododermatitis. Large interdigital plaque with crusts and ulcers (culture positive for coagulase‐positive Staphylococcus sp., E. coli, and Actinomyces sp.). Figure 5.1-12 Abscess. Fluctuant abscess at commissure of lips. Miscellaneous Bacterial Diseases Abscess (Fig. 5.1‐12) Common and cosmopolitan; anywhere; usually penetrating wounds; subcutaneous firm to fluctuant nodules; especially C. pseudotuberculosis, T. pyogenes, and Streptococcus equi subsp. zooepidemicus (“alpaca fever” in South America); tooth root abscesses usually appear as mandibular nodules or abscesses with Actinomyces spp. and other anaerobes. Bacterial One case report in an alpaca; single‐ or multiple‐crusted, ulcerated nodules; especially legs; S. aureus; culture pseudomycetoma and dermatohistopathology (“botryomycosis”) Opportunistic Very rare and regional (Australia) in alpacas; Mycobacterium ulcerans; wound contamination; usually solitary mycobacterial nonhealing ulcer; especially leg or face; culture, PCR, and dermatohistopathology infection Actinobacillosis One anecdotal case report in an alpaca with no details; Actinobacillus lignieresi; culture and dermatohistopathology Nocardiosis Very rare and mostly anecdotal in llamas; abscesses; wound contamination; Nocardia asteroides; culture, PCR, and dermatohistopathology Clostridial cellulitis Anecdotal in alpacas; Clostridium septicum; “malignant edema”; culture Necrobacillosis Sporadic and cosmopolitan; wound contamination by Fusobacterium necrophorum biotypes A and B; especially lips, interdigital spaces, and footpads; moist, necrotic, ulcerative, and foul smelling; variable lameness and systemic signs; culture 300 Section 5: Camelid References Clark, M.D., et al. (2013) Cytology of the interdigital skin O’Brien, C., et al. (2013) Mycobacterium from healthy alpacas (Vicugna pacos). Jpn J Vet Dermatol ulcerans infection in two alpacas. Aust Vet J 19, 63–67. 91, 296–300. Clark, M.D., et al. (2013) Resident flora of the interdigital Rosychuk, R.A.W. (1989) Llama dermatology. Vet Clin N skin from healthy alpacas (Vicugna pacos). Jpn J Vet Am Food Anim