Idiopathic hyperkeratosis (commonly called munge in New World Camelids) represents one of the most perplexing and commonly encountered dermatologic conditions in llamas and alpacas.
Overview and Clinical Importance
Idiopathic hyperkeratosis (commonly called munge in New World Camelids) represents one of the most perplexing and commonly encountered dermatologic conditions in llamas and alpacas. This hyperkeratotic skin disorder is characterized by thickening of the stratum corneum, resulting in crusting, scaling, and alopecic lesions that can significantly impact animal welfare, fiber quality, and show appearance. The condition encompasses several related syndromes including zinc-responsive dermatosis, idiopathic necrolytic neutrophilic hyperkeratosis (INNH), and focal perioral/perinasal dermatitis.
For cervids (deer, elk, moose), true idiopathic hyperkeratosis similar to camelid munge is not a recognized clinical entity. However, cervids experience various hyperkeratotic skin conditions secondary to ectoparasitic infestations (demodectic mange, sarcoptic mange), bacterial infections (dermatophilosis), and viral diseases (cutaneous fibromas). Understanding these differential diagnoses is crucial for the NAVLE examination.
| Feature |
Clinical Significance |
| Thick Skin |
Thicker than other domesticated ruminants, especially on neck and feet; males with high testosterone may have 2-3x thicker neck skin for jugular protection |
| Minimal Lanolin |
Fewer sebaceous glands produce very little lanolin compared to sheep; increases risk of clipper burn and reduces effectiveness of topical pour-on medications |
| Hair Follicle Orientation |
Oblique orientation in thick-fleeced areas provides insulation; perpendicular in thinner-fleeced areas |
| Fiber Types |
Primary guard hairs (thick) and secondary hairs (fine) in 1:9 ratio in llamas; alpacas have fewer/absent primary hairs |
| Hyperkeratosis Prone |
Skin quickly develops thick outer keratin layer in response to inflammation (elephant-like appearance) |
Camelid Skin Anatomy and Unique Characteristics
Understanding camelid skin physiology is essential for diagnosing and treating hyperkeratotic conditions. New World Camelids have unique dermatologic features that affect disease presentation and treatment response.
Key Anatomical Features
High-YieldThe lack of lanolin in camelid skin means pour-on formulations designed for cattle are significantly less effective. Subcutaneous injections are the preferred route for systemic antiparasitic treatment in camelids.
| Condition |
Clinical Features |
Key Characteristics |
| Zinc-Responsive Dermatosis |
Nonpruritic papules with tightly adherent crusts
Progress to plaques and thickened crusting
May wax and wane |
Less densely haired areas: perineum, ventral abdomen, inguinal region, medial thighs, axilla
Young animals (1-2 years) predisposed
Dark-fleeced animals more susceptible |
| INNH (Munge) - Focal Form |
Heavy, adherent hyperkeratotic crusts
Wrinkling, thickening, cracking at mouth corners
Crusty scales on lips and nose |
PERINASAL and PERIORAL regions primarily
May extend to periocular and periaural areas
Severe cases: crusts may obstruct nostrils |
| INNH (Munge) - Diffuse Form |
Widespread hyperkeratotic plaques
Alopecic with variable skin thickness
Inflammatory lesions may wax and wane |
More commonly seen in young llamas (1-2 years)
Multiple body regions affected
Often associated with secondary bacterial infection |
| Ichthyosis |
Focal or diffuse nonpruritic, nonpainful hyperkeratotic plaques
Prominent laminated orthokeratotic hyperkeratosis |
CONGENITAL - present at birth or shortly after
Genetic abnormality in keratinocyte sloughing
Absence of inflammatory cells on histology |
Classification of Hyperkeratotic Conditions in Camelids
Hyperkeratotic skin conditions in New World Camelids include several overlapping syndromes that may represent different manifestations of related pathologic processes. The terminology can be confusing, but understanding these distinctions is critical for the NAVLE.
| Condition |
Primary Location |
Pruritus |
| Zinc-Responsive |
Perineum, ventral abdomen, inguinal region, medial thighs, axilla, medial forearms |
ABSENT (nonpruritic) |
| Munge (Focal) |
Perinasal, perioral, periocular, periaural regions |
ABSENT (nonpruritic) |
| Sarcoptic Mange |
Lower legs, belly, tail, interdigital spaces, lips, ears, ventral abdomen, face |
INTENSE pruritus - key differentiator |
| Chorioptic Mange |
Interdigital spaces of forefeet predominantly |
VARIABLE (mild to moderate) |
Etiology and Pathophysiology
Zinc-Responsive Dermatosis
The pathophysiology of zinc-responsive dermatosis remains incompletely understood. The condition may represent either a true zinc deficiency or a keratinizing disorder that responds to supraphysiologic doses of zinc supplementation. Key contributing factors include:
- Dietary factors: High-calcium diets (alfalfa hay, lucerne) interfere with zinc absorption through competitive inhibition
- Metabolic factors: Camelids naturally have lower serum zinc levels than other ruminants, making interpretation of blood zinc difficult
- Fleece color predisposition: Dark-fleeced animals are more susceptible, possibly due to higher zinc and copper requirements in pigmented fiber production
- Age susceptibility: Young breeding females (1-2 years) at highest risk due to increased mineral demands
INNH (Munge)
INNH is likely a cutaneous reaction pattern in New World Camelids caused by complex interactions between host factors, environmental conditions, and various pathogens. Potential initiating factors include:
- Bacterial folliculitis and dermatophilosis
- Dermatophytosis (fungal infection)
- Mite infestation (Sarcoptes, Chorioptes, Psoroptes)
- Fly bites and contact dermatitis
- Viral papillomas/fibropapillomas
- Immunodeficiency (juvenile llama immunodeficiency syndrome)
NAVLE TipOn the NAVLE, remember that many cases initially diagnosed as munge actually turn out to be SARCOPTIC MANGE on further workup. Always recommend skin scrapings and/or biopsy before definitively diagnosing idiopathic hyperkeratosis.
| Condition |
Histopathologic Findings |
| Zinc-Responsive |
Prominent laminated orthokeratotic hyperkeratosis of epidermis and hair follicle infundibula with minimal epidermal hyperplasia |
| INNH (Munge) |
Parakeratotic AND orthokeratotic hyperkeratosis, seropurulent palisading crust, epidermal hyperplasia, degenerate neutrophils, keratinocyte necrosis, epidermal edema |
| Ichthyosis |
Prominent laminated orthokeratotic hyperkeratosis; ABSENCE of inflammatory cells (key differentiator from zinc-responsive) |
| Sarcoptic Mange |
Eosinophilic interstitial dermatitis, marked parakeratotic hyperkeratosis, mites within surface crusts or epidermis, eosinophilic microabscesses |
| Chorioptic Mange |
Eosinophilic epidermal microabscesses, pustules, eosinophilic interstitial dermatitis, mites in surface crusts |
Clinical Presentation
Anatomic Distribution by Condition
| Differential |
Key Features |
Diagnostic Test |
| Sarcoptic Mange |
INTENSE pruritus, alopecia, erythema, crusting; zoonotic potential |
Deep skin scrapings; biopsy if negative scrapings |
| Dermatophilosis |
Crusty scabs, exudative dermatitis; wet/warm conditions; Dermatophilus congolensis |
Cytology showing branching filamentous bacteria; culture |
| Dermatophytosis |
Circular alopecic patches with scaling; Trichophyton spp |
Fungal culture; Wood's lamp (variable) |
| Contagious Ecthyma (Orf) |
Muzzle lesions; papillomatous appearance; ZOONOTIC |
PCR; electron microscopy |
| Bacterial Dermatitis |
Pustules, crusting, often secondary to primary condition |
Culture and sensitivity |
| Immune-Mediated Disease |
Pemphigus-like conditions; vesicles, erosions |
Histopathology with immunofluorescence |
Diagnostic Approach
A systematic diagnostic approach is essential because multiple conditions can cause similar clinical signs. Skin biopsy is the gold standard for diagnosis, but other tests provide valuable information.
Step 1: Skin Scrapings
Deep skin scrapings are essential to rule out mange mites. Critical points:
- Multiple scraping sites recommended (same individual and several herd members)
- Use blunted scalpel blade coated with liquid paraffin
- Chorioptic mites: scrape interdigital spaces of forefeet
- Sarcoptes: scrape crusty areas and affected regions
- CRITICAL: Negative skin scrapings do NOT rule out mange - mites often difficult to find in acute cases
Step 2: Skin Biopsy and Histopathology
Step 3: Serum Zinc Analysis
Important caveat: Normal serum zinc levels do NOT rule out zinc-responsive dermatosis. Camelids naturally have lower serum zinc than other species, making interpretation difficult. Some animals respond to zinc supplementation despite normal serum levels.
High-YieldThe diagnosis "zinc-responsive dermatosis" has become OVERUSED and is seldom proven correct. Always pursue thorough diagnostic workup before defaulting to this diagnosis. Many cases initially attributed to zinc deficiency are actually sarcoptic mange or other conditions.
| Treatment |
Dose |
Notes |
| Zinc Sulfate |
1 g/day PO |
First-line treatment; response expected within 3-6 weeks |
| Zinc Methionine |
2-4 g/day PO |
Better bioavailability than zinc sulfate |
| Dietary Modification |
See notes |
DISCONTINUE alfalfa hay; minimize calcium supplementation (calcium interferes with zinc absorption) |
Differential Diagnosis
A comprehensive differential list is essential for NAVLE success. The key differentials for hyperkeratotic skin conditions in camelids include:
| Treatment Category |
Options |
Application |
| Topical Antimicrobials |
Gentamicin, chlorhexidine scrub, Nolvasan |
Daily application to affected areas after gentle crust removal |
| Topical Steroids |
Betamethasone (Betagen spray) |
Use with caution - may cause abortion in pregnant females |
| Camelid Skin Mix (Witches Brew) |
Ivermectin + DMSO + Mineral oil + Gentamicin |
Popular anecdotal treatment; DMSO delivers ivermectin through crusts; gentamicin treats secondary infection |
| Zinc Supplementation |
1 g zinc sulfate or 2-4 g zinc methionine daily |
Often included as adjunct therapy |
Treatment Protocols
Zinc-Responsive Dermatosis Treatment
INNH (Munge) Treatment
Because the etiology of INNH is unknown and multifactorial, treatment often involves a "kitchen sink" approach. Cases may respond to various combinations of the following:
Mange Treatment (If Sarcoptic/Chorioptic/Psoroptic Mites Confirmed)
NAVLE TipSarcoptic mange treatment in camelids requires PROLONGED THERAPY (often 6 months or more). Treatment failure is common due to: 1) Poor absorption of pour-on products due to lack of lanolin, 2) Chorioptes resistance to standard macrocyclic lactone doses, 3) Environmental re-infestation. Always treat ALL animals in the herd and consider moving to clean pasture after treatment.
| Drug |
Dose and Route |
Notes |
| Ivermectin |
0.2 mg/kg SQ every 10-14 days |
Effective for Sarcoptes and Psoroptes; Chorioptes may require additional topical therapy; oral route LESS EFFECTIVE in camelids |
| Moxidectin |
0.2 mg/kg SQ every 3 weeks |
May require 6-8 treatments for complete resolution; llamas respond slower than alpacas |
| Amitraz (Topical) |
50 mL in 10 L water topically |
Useful for refractory cases; preceded by antibacterial or keratolytic shampoo |
| Eprinomectin |
0.5 mg/kg topical weekly x 4 weeks |
Reduces but may not eradicate Chorioptes; less effective than SQ ivermectin for sarcoptic mange |
Prognosis
Zinc-responsive dermatosis: Good prognosis with appropriate zinc supplementation and dietary modification. Response typically seen within 3-6 weeks.
INNH (Munge): Variable prognosis. Some cases spontaneously regress; others require prolonged treatment. Refractory cases may indicate underlying immunodeficiency (juvenile llama immunodeficiency syndrome) requiring further workup.
Sarcoptic Mange: Guarded prognosis without aggressive treatment. Can be fatal in severe cases. Complete eradication may require 6+ months of treatment.
Ichthyosis: Poor prognosis for resolution (congenital). Treatment typically not attempted; condition is primarily cosmetic.
| Condition |
Clinical Features |
Key Points |
| Demodectic Mange |
Patchy to generalized alopecia, epidermal crusts, cutaneous nodules over head, neck, limbs, trunk |
Most common cause of infectious dermatologic disease in white-tailed deer; mild perifollicular lymphoplasmacytic inflammation |
| Dermatophilosis |
Crusting, erythema, alopecia on face, ears, distal extremities; crusty scabs |
Caused by Dermatophilus congolensis; more common in young males less than 1 year; associated with wet, warm conditions; ZOONOTIC |
| Cutaneous Fibromas (Warts) |
Firm, fleshy nodular masses attached to skin; gray/dark surface; may be pendulous |
Papillomavirus; species-specific; common on head, neck, shoulders; benign; immune system usually eliminates over time |
| Sarcoptic Mange |
Severe pruritus, alopecia, hyperkeratosis, crusting; can be fatal |
Less common in cervids than in camelids; treatment rarely attempted in wildlife |
Cervidae (Deer and Elk) Hyperkeratotic Skin Conditions
Important distinction: True idiopathic hyperkeratosis (munge) as seen in camelids is NOT a recognized clinical entity in cervids. However, cervids experience various skin conditions that can produce hyperkeratotic lesions as secondary manifestations.
Common Cervid Skin Conditions with Hyperkeratotic Features
| Condition |
Species |
Key Diagnostic Feature |
Primary Treatment |
| Zinc-Responsive |
Camelids |
Less-haired areas; orthokeratotic hyperkeratosis |
Zinc 1-4 g/day; discontinue alfalfa |
| INNH (Munge) |
Camelids |
Perioral/perinasal; neutrophilic/necrotic histology |
Multimodal: antimicrobials, zinc, steroids |
| Sarcoptic Mange |
Both |
INTENSE PRURITUS; mites on scraping/biopsy |
Ivermectin 0.2 mg/kg SQ q10-14d x 6+ months |
| Dermatophilosis |
Both |
Wet conditions; branching bacteria on cytology |
Usually self-limiting; antibiotics if severe |
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