**4. Discussion**

This study examined the immune response in the dermis of the wolf, fox, chamois and red deer from Northern Spain against natural *S. scabiei* infestation. We identified macrophages as the predominant cells in lesions of all four species, and we found small differences in the immune response among species.

Our observation that fox lesions contained the highest number of inflammatory cells may mean that the animals were in a more severe stage of the disease, or it may mean that their immune response of macrophages and lymphocytes was unable to control disease progression based on the generalized and crust lesions observed in those animals [6,8]. We cannot exclude that the higher cell number reflects higher parasitic burden [5], but this seems less likely, since chamois and red deer showed less intense inflammatory response despite high parasite burden [5]. Instead, the less intense response in the wolf, chamois and red deer may reflect some kind of adaptation or tolerance between the host and parasite [6,16]. These results should be verified and extended in further studies, especially since they varied appreciably among species and individuals within each species.

In all four species, macrophages were the most abundant inflammatory cells in skin lesions, ye<sup>t</sup> the proportions varied across species. Lesions from the wolf showed a higher percentage of macrophages than lesions from other species, while lesions from fox and chamois showed a higher percentage of plasma cells and T lymphocytes, respectively. This may help explain species differences in hypersensitivity responses [5,16]. Ungulates and some fox populations tend to show immediate type I hypersensitivity response with higher eosinophil counts, while the wolf and other fox populations tend to show delayed type IV hypersensitivity response with higher macrophage counts [5]. Higher macrophage count may help explain the greater efficacy of a type IV hypersensitivity (alopecic) response in the wolf for eliminating *S. scabiei* [5]. The lower percentage of macrophages in foxes, chamois and red deer in the present study, together with the higher number of eosinophils previously observed in mange lesions [5], may result primarily in hyperkeratotic lesions related to a late phase of the type I hypersensitivity response pointing towards type IV hypersensitivity [6].

The higher proportion of plasma cells in fox than those of T and B lymphocytes might sugges<sup>t</sup> a stronger humoral response [17]. In contrast, chamois in our study showed a larger proportion of T lymphocytes than B lymphocytes and plasma cells, consistent with previous work [8], confirming that in this species the cellular immune response is much stronger than the humoral response to *S. scabei* infestation [17]. That response may be related to the severe hyperkeratotic type lesions in our animals, which might reflect the ineffective T helper 2 (Th2) lymphocyte-type immune response [8]. In fact, excessive signaling by Th2 lymphocytes can trigger atopies or allergies [12]. The relative

proportions of the di fferent types of inflammatory cells may translate to di fferences in immune e fficacy against *S. scabiei* infestation. Future studies should explore the factors that influence the nature and efficacy of the immune response against *S. scabiei*, which likely include body condition, sex, age, clinical stage, concomitant presence of immunosuppressive pathogens and sampling season [9]. Our results illustrate how immunohistochemistry of skin samples from wild species a ffected by sarcoptic mange can be useful for analyzing the immune response to infestation.
