Pathology Case of the Month - Timber Wolf

Gross Findings:

External: There is severe, extensive alopecia. Alopecic skin is dark gray and thickened. Multifocal, moderate to marked, yellow to brown crusting of skin is present, and there are several linear excoriations. The peripheral lymph nodes are moderately enlarged. Several superficial bite wounds are present on the head, neck, and cranial thorax.

Internal: There is a scant subcutaneous, visceral, and epicardial fat.

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Histopathological Findings:

There is multifocal, moderate to severe acanthosis and parakeratotic hyperkeratosis. Multiple subcorneal, 250-400 um in diameter arthropods with short thick legs and wide angled, V shaped dorsal spines are present in areas of hyperkeratosis. There are rare subcorneal pustules. Many hair follicles lack shafts, and there is a diffuse, moderate to marked, increase in dermal collagen.

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Morphologic Diagnoses:

1. Chronic, severe, multifocal alopecia with lichenification and serocellular crusting.
2. Chronic, marked, multifocal acanthosis and parakeratotic hyperkeratosis with intralesional mites.

Disease: Sarcoptic mange

Etiology: Sarcoptes scabiei

Distribution: Sarcoptes scabiei has a global distribution.

Seasonality: Disease may occur at any time of the year.

Host Range: Worldwide, S. scabiei is known to infest over 100 species of domestic and wild mammals. In North America, the most commonly affected wildlife species are timber wolves (Canis lupus), red fox (Vulpes vulpes), coyotes (Canis latrans), and black bears (Ursus americanus). Sarcoptic mange has also been reported in red wolves (Canis rufus) and Mexican wolves (Canis lupus baileyi) in North America.

Transmission: Sarcoptic mange is a highly contagious skin disease. Transmission is by direct contact or through shared environments, such as dens, or objects used for rubbing of the skin due to pruritis.  

Clinical Signs: Intense pruritis, with alopecia, erythema, and crusting of the skin. Secondary bacterial and/or yeast infections of the skin, occasionally leading to sepsis, may occur. Sepsis or hypothermia may result in death.

Pathology: Alopecia, acanthosis, parakeratotic hyperkeratosis, eosinophilic and lymphocytic dermatitis, with evidence of mites tunneling within the epidermis. In more chronic cases, mites may be scarce or absent, and there is increased lichenification and thickening of dermal collagen.

Diagnosis: Cytologic or histopathologic identification of S. scabiei mites in the skin of an affected animal is diagnostic for sarcoptic mange. In some cases, serum antibody testing or PCR may be useful.

Public Health Concerns: Limited infestations of S. scabiei may occur in humans that have handled affected animals.

Wildlife Population Impacts: Epizootics of sarcoptic mange in wolves can be a source of significant mortality. Mange was the cause of 27% of collared wolf mortality in Wisconsin in 2002-2003. Decreased pup recruitment has been observed during epizootics.

Management: Management strategies for this endemic disease are limited. Proper biosecurity should be used when handling or transporting potentially infested animals. Individual treatment of infested animals is usually reserved for endangered species, research animals, or during relocation.  

References:

Angelone-Alasaad S, Molinar Min A, Pasquetti M, Alagaili AN, D'Amelio S, Berrilli F, Obanda V, Gebely MA, Soriguer RC, Rossi L. 2015. Universal conventional and real-time PCR diagnosis tools for Sarcoptes scabiei. Parasit Vectors 8:587

Fuchs B, Zimmermann, B, Wabakken, P. et al. 2016. Sarcoptic mange in the Scandinavian wolf Canis lupus population. BMC Vet Res 12:156.  https://doi.org/10.1186/s12917-016-0780-y

Niedringhaus KD, Brown JD, Sweeley KM, Yabsley MJ. 2019. A review of sarcoptic mange in North American wildlife. International journal for parasitology. Parasites and wildlife, 9, 285–297. https://doi.org/10.1016/j.ijppaw.2019.06.003

Pence DB, Ueckermann E. 2002. Sarcoptic mange in wildlife. Rev. Sci. tech. Off. int. Epiz. 21(2) 385-398.

Wydeven AP, Wiedenhoeft JE. 2004. Status of the timber wolf in Wisconsin, performance report 1 July 2003 through 30 June 2004. Bureau of Endangered Resources, Wisconsin Department of Natural Resources, Park Falls, Wisconsin.