Camelidae and Cervidae Hyperkeratosis – NAVLE Study Guide

Overview and Clinical Importance

Hyperkeratosis refers to the abnormal thickening of the stratum corneum, the outermost layer of the epidermis. In both camelids (llamas, alpacas) and cervids (deer, elk, moose), hyperkeratotic conditions represent significant dermatological challenges with diverse etiologies including nutritional deficiencies, parasitic infestations, infectious agents, and congenital disorders.

Hyperkeratotic lesions in these species are typically characterized by alopecia, thickened skin, adherent crusts, and scaling. The pathophysiology varies by etiology but generally involves either increased keratinocyte proliferation, decreased desquamation, or both.

Part I: Hyperkeratotic Conditions in Camelidae

New World Camelids (llamas, alpacas, vicunas, guanacos) have unique skin characteristics that predispose them to specific dermatological conditions. Camelids are particularly susceptible to zinc deficiency and idiopathic hyperkeratotic syndromes.

Zinc-Responsive Dermatosis (Idiopathic Hyperkeratosis)

Etiology and Pathophysiology

Zinc-responsive dermatosis occurs in llamas and alpacas of any age. The pathogenesis remains poorly understood. Affected animals may have low serum zinc concentrations (less than 0.30 micrograms/mL), but many respond to zinc supplementation despite normal serum levels. Young adult camelids (1-2 years) appear predisposed, and colored fleece animals are more commonly affected. High dietary calcium and alfalfa hay may interfere with zinc absorption.

Clinical Signs

• Nonpruritic papules with tightly adherent crusts
• Progression from papules to plaques to large areas of thickening and crusting
• Lesions most common in less densely haired areas: perineum, ventral abdomen, inguinal region, medial thighs, axillae, medial forearms
• Face may also be involved (bridge of nose, muzzle, periocular region, pinnae)
• Clinical signs may wax and wane

Diagnosis

Skin biopsy is the diagnostic method of choice. Histopathology reveals marked parakeratotic and orthokeratotic hyperkeratosis with epidermal hyperplasia. Inflammatory cells are typically present, which helps distinguish this condition from ichthyosis. The proposed reference range for serum zinc in llamas is 0.30-0.50 micrograms/mL.

Treatment

Idiopathic Necrolytic Neutrophilic Hyperkeratosis (Munge)

Etiology and Pathophysiology

Munge (also called INNH) is a severe, poorly understood hyperkeratotic condition in camelids. It likely represents a cutaneous reaction pattern to various triggers. Two forms exist: Focal INNH affects perinasal and perioral regions; Diffuse INNH is typically seen in young llamas (1-2 years).

Clinical Signs

• Heavy, adherent, hyperkeratotic crusts in paranasal and perioral regions
• Bridge of nose, periocular, and periaural regions may be affected
• Severe cases: thick crusts may obstruct nostrils
• Dark-haired animals appear predisposed

Diagnosis

Multiple deep skin scrapings should be performed to rule out sarcoptic mange (many cases of suspected munge are actually sarcoptic mange). Skin biopsy reveals parakeratotic hyperkeratosis with seropurulent crusts, epidermal hyperplasia, and keratinocyte necrosis.

Differential Diagnoses

• Sarcoptic mange (CRITICAL to rule out)
• Viral contagious pustular dermatitis
• Dermatophilosis
• Dermatophytosis (ringworm)
• Immune-mediated disease

Mange Mite Infestations in Camelids

Mange mites represent the most common cause of pruritic hyperkeratosis in camelids. Three genera are primarily involved: Sarcoptes, Chorioptes, and Psoroptes. Mixed infestations are common.

Diagnosis

Skin scrapings are the primary diagnostic tool, but mite detection can be challenging. In one study, only 28% of animals with clinical lesions tested positive. Chorioptic mites are most readily recovered from the interdigital spaces of the forefeet. Sarcoptic mange often requires biopsy for confirmation.

Treatment

Important: Organophosphate dips are NOT recommended for camelids due to stress. All contact animals should be treated.

Ichthyosis

Ichthyosis is a rare congenital disorder characterized by focal or diffuse hyperkeratosis and scaling. Lesions are present at birth with nonpruritic, nonpainful hyperkeratotic plaques. Histopathology shows laminated orthokeratotic hyperkeratosis with minimal epidermal hyperplasia and absence of inflammatory cells (distinguishing feature from zinc-responsive dermatosis). Treatment is generally not attempted.

Part II: Hyperkeratotic Conditions in Cervidae

Cervids (deer, elk, moose, caribou, reindeer) are susceptible to various skin conditions that produce hyperkeratotic lesions. The most clinically significant include cutaneous fibromas (papillomatosis), dermatophilosis, and mange mite infestations.

Cutaneous Fibromas (Deer Warts)

Etiology and Pathophysiology

Cutaneous fibromas (deer warts, fibropapillomas) are benign neoplasms caused by species-specific papillomaviruses. The viruses cause proliferation of epithelial cells and dermal fibroblasts. Histologically, tumors show hyperkeratosis and acanthosis of the epidermis. Fibromas have been reported in white-tailed deer, mule deer, elk, moose, red deer, roe deer, fallow deer, caribou, and Sika deer.

Clinical Signs

• Firm, nodular masses fastened only to the skin
• Size varies from less than 1 cm to greater than 10 cm diameter
• Color: gray, black, or tan; surface may be smooth or roughened (cauliflower-like)
• Most common locations: head, neck, face, forelegs, shoulders
• Usually single or few; occasionally 25 or more
• Lesions typically regress spontaneously as immune response develops

Clinical Significance

Species-specific: The papillomavirus is species-specific and does NOT infect humans, pets, or livestock. Fibromas are NOT an important cause of deer mortality. Meat is safe for human consumption unless there is secondary bacterial infection.

Dermatophilosis (Rain Rot)

Etiology and Pathophysiology

Dermatophilosis (rain rot, lumpy wool disease) is a bacterial skin infection caused by Dermatophilus congolensis, a gram-positive actinomycete with a life cycle resembling that of a fungus. It affects white-tailed deer, mule deer, elk, moose, and many other species.

Clinical Signs

• Raised, matted tufts of hair that resemble paint brushes
• Crusts, scabs, and hair loss
• Lesions most common on areas chronically wet: back, face, ears, legs
• Histopathology: alternating layers of parakeratotic hyperkeratosis and bacterial hyphae

Diagnosis and Treatment

Diagnosis: Characteristic paint brush tufts; impression smears show branching hyphae with parallel rows of coccoid cells (railroad track appearance). Most wildlife recover spontaneously within 3 weeks if skin dries out. In captive animals, systemic antimicrobials (penicillin, trimethoprim-sulfa) may be used.

Zoonotic Potential

ZOONOTIC: Dermatophilosis can be transmitted to humans through direct contact. Infection in humans is usually self-limiting. Hunters should wear gloves when handling affected deer.

Mange Mite Infestations in Cervids

Cervids are susceptible to various mange mites, with Sarcoptes scabiei, Psoroptes species, and Demodex species being most significant.

Summary: Comparison of Hyperkeratotic Conditions