Pathology of Sarcoptic Mange in Red Foxes (Vulpes Vulpes): Macroscopic and Histologic Characterization of Three Disease Stages

Abstract

ABSTRACT:Sarcoptic mange is a highly contagious skin disease that can have a devastating impact on affected wild mammal populations. There are notable variations in the clinical and pathologic picture of sarcoptic mange among species and among conspecifics. However, the origin of these variations is unclear. We propose a classification scheme for skin lesions associated with Sarcoptes scabiei infestation to provide a basis for a subsequent risk factor analysis. We conducted a casecontrol study focused on macroscopic and histologic examination of the skin, using 279 red foxes (Vulpes vulpes) found dead or shot in Switzerland between November 2004 and February 2006. All animals were submitted to gross necropsy following a detailed protocol. Selection criteria for cases (n5147) vs. controls (n5111) were the presence or absence of mange-like lesions, mite detection by isolation or histologic examination, and serologic testing for S. scabiei antibodies. Characteristic features of mange lesions were scored macroscopically in all foxes and histologically in 67 cases and 15 controls. We classified skin lesions and associated necropsy findings into three types of mange: A) early stage (n545): focal-extensive skin lesions, thin crusts, mild to moderate alopecia, few mites, numerous eosinophils, and mild lymph node enlargement; B) hyperkeratotic, fatal form (n586): generalized skin lesions, thick crusts with or without alopecia, foul odor, abundance of mites, numerous bacteria and yeasts, numerous lymphocytes and mast cells, severe lymph node enlargement, and emaciation; C) alopecic, healing form (n516): focal lesions, no crusts, severe alopecia, hyperpigmentation and lichenification, absence of mites, mixed cell infiltration, and rare mild lymph node enlargement. We hypothesize that after stage A, the animal either enters stage B and dies, or stage C and survives, depending on largely unknown extrinsic or intrinsic factors affecting the host ability to control mite infestation.

The taxonomy, life cycle and pathology of Sarcoptes scabiei and Notoedres cati (Acarina, Sarcoptidae): A review in a Fennoscandian wildlife perspective

“…The complex immunology in the epidermis and dermis of affected hosts is not well understood at the species level (Nimmervoll et al 2013; but see Kuhn et al 2008), and the following generalization of host immunology is regarded to be representative to Fennoscandian wildlife. Certain components in extract from scabies mites modulate the inflammatory/ immune reaction during infestation (Arlian et al 2003).…”

“…The mite-host-specific mechanisms responsible for various outcomes of infestations are yet largely unknown, and further research is needed. Macroscopical and histological results from red foxes suggested three different disease stages (Nimmervoll et al 2013). The first stage is characterized by extensive skin lesions, thin crusts, mild to moderate alopecia, low parasite burden, numerous eosiniophils, and slightly swollen nymph nodes.…”

“…The second stage may possibly be lethal to red foxes. Survival depends on largely unknown extrinsic factors or intrinsic immunological factors affecting the animal's ability to cope with the mite infestation (Nimmervoll et al 2013). In conclusion, development of chronic mange in wild mammals normally requires transmission of an adequate species-specific mite between conspecific hosts, and inter-specific transmission rarely result in chronic or fatal illness.…”

“…The role of IgE in host immunity to psaroptic scabies mite (Psoroptes ovis) has also been documented (Stromberg & Fisher 1986;Stromberg & Guillot 1989). The mechanisms underlying immunity responses seem to vary between species (Nimmervoll et al 2013) and experiments with repeated infestations with S. scabiei show a wide range of immune responses ranging from no immunity to acquired full immunity.…”

“…A long-term study of scabies in red foxes shot by hunters in Norway indicated that the population to some degree could cope with the parasite over time. Low-grade or subclinical infections and even recoveries have been documented (Davidson et al 2008;Nimmervoll et al 2013). However, such trends may be unstable due to the ongoing arms race between parasites and hosts.…”