Signalment and History

This juvenile, intact male red fox was found near a strip mall and admitted to a wildlife rehabilitation center, where it was noted to be lethargic and emaciated, with generalized alopecia and crusting skin lesions. Due to the poor prognosis, the animal was euthanized.

Gross Findings

The animal was emaciated. The skin over the entire body but particularly the head, dorsum and legs were multifocally and severely alopecic and scaly. The peripheral lymph nodes and the medial iliac lymph nodes were mildly to moderately enlarged.

Figure 1: The skin over the entire body was diffusely covered with thick crusts forming deep skin fissures.

Figure 2: Cross section of haired skin is markedly thickened and irregular, with severe diffuse hyperkeratosis forming a thick, friable, tan to yellow-brown crust overlying the epidermal surface.

Figure 3: Medial aspect of the right front limb. The prescapular lymph node was moderately enlarged. Please also note the flaky skin along the periphery.

Histopathology

Skin (Figure 4): Diffusely, the epidermis is thickened with numerous areas of acanthosis, prominent rete ridges, and orthokeratotic and parakeratotic hyperkeratosis. Within the stratum corneum, often within tunnels, are adult arthropods characterized by a thin cuticle with spines, skeletal muscle (Figure 5), jointed appendages, and intermittently containing ova. The dermis is infiltrated by small numbers of mast cells and occasional eosinophils. Multifocally, arising from the epidermis are pustules containing variable amounts of degenerate neutrophils, bacterial aggregates and necrotic debris.

Lymph node: The lymphoid follicles are increased in size and number. The medulla contains numerous histiocytes.

Figure 4: Skin, Diffuse, severe hyperkeratosis with intralesional arthropods (arrow) and overlying serocellular crust.

Figure 5. Skin. Higher-magnification view of the skin lesion highlighting Sarcoptes scabiei within the epidermis; please note the striated muscle fibers of the arthropod.

Ancillary Testing

• Parasitology: Colonic contents were negative for parasites by floatation analysis.

Morphologic Diagnosis

1. Skin:
   1. alopecia, multifocal, marked
   2. epidermal hyperplasia and hyperkeratosis, multifocal, marked, chronic with numerous intracorneal mites morphologically consistent with Sarcoptes scabiei
2. Lymph nodes, lymphoid hyperplasia, diffuse, marked, chronic with medullary histiocytosis

Etiology

Sarcoptes scabiei (sarcoptic mange).

Comments

Sarcoptic mange is a parasitic skin disease caused by the burrowing mite Sarcoptes scabiei. This condition affects a wide range of host species, including humans, and is commonly reported in wildlife. Among wild carnivores, the red fox (Vulpes vulpes) is one of the species most frequently affected. According to reports from wildlife rehabilitation center in Minnesota, the first clinically affected red foxes are typically observed in early fall. Although sarcoptic mange is potentially treatable in its early stages, affected foxes often experience progressive alopecia, severe pruritus, and secondary skin infections. As the disease advances, many individuals develop emaciation and debilitation, ultimately resulting in a poor prognosis despite the initially favorable outlook.

Sarcoptes scabiei exhibits a degree of host adaptation that influences transmission dynamics and limits cross-species persistence. Experimental transmission studies conducted in North America demonstrated that S. scabiei var. vulpes readily establishes infection in red foxes and can be successfully transmitted to domestic dogs and coyote–dog hybrids, whereas sustained infestation could not be achieved in skunks, rabbits, gray foxes, raccoons, opossums, rodents, or cats. These observations support the concept of host-adapted mite variants and help explain the predominance of sarcoptic mange within specific wildlife populations despite frequent interspecies contact.

Gross lesions range from focal areas of alopecia with thin, adherent crusts in early disease to generalized, severe hyperkeratotic dermatitis characterized by thick, fissured, gray-yellow to brown crusts, skin thickening, and a foul odor in advanced cases. Severely affected animals are frequently emaciated and exhibit generalized lymphadenomegaly due to lymphoid hyperplasia. Histologically, the skin is characterized by a marked ortho- and parakeratotic hyperkeratosis, epidermal hyperplasia with elongated rete ridges, and variable crust formation containing numerous Sarcoptes scabiei mites, along with secondary bacteria or yeasts. The inflammatory infiltrate in the superficial dermis is usually fairly subtle.

References

1. Nimmervoll H, Hoby S, Robert N, Lommano E, Welle M, Ryser-Degiorgis MP. Pathology of sarcoptic mange in red foxes (Vulpes vulpes): macroscopic and histologic characterization of three disease stages. J Wildl Dis. 2013 Jan;49(1):91-102. doi: 10.7589/2010-11-316. PMID: 23307375.
2. “Mange in the Red Fox.” Wildlife Online, wildlifeonline.me.uk/articles/view/mange-in-the-red-fox. Accessed 25 Jan. 2026.
3. Wildlife Rehabilitation Center of Minnesota. “Critical Care of an Emaciated Mange Fox.” WRCMN, https://wrcmn.org/case-study/43/Critical-Care-of-an-Emaciated-Mange-Fox/. Accessed 25 Jan. 2026.