Background: Although alopecia is a commonly recognized problem affecting many captive Rhesus macaque colonies, there is no consensus as to the underlying etiology or appropriate course of management.
Methods: We performed skin biopsies to assess underlying pathology in alopecic Rhesus macaques and performed immunohistochemical and metachromatic staining of these biopsies to assess the cellular infiltrates.
Results: Alopecia is associated with superficial dermal perivascular mononuclear cell infiltrates and skin pathology consistent with chronic hypersensitivity dermatitis. The inflammation is primarily composed of CD4+ cells admixed with histiocytes and mast cells. Inflammation is correlated with degree of alopecia. Further analysis in different groups of macaques revealed that animals born outdoors or infected with lung mites had reduced dermal inflammatory cell infiltrates and a lower incidence of alopecia.
Conclusions: These findings support a hypothesis that an altered housing status resulting in decreased pathogen burden in Rhesus macaque colonies may contribute to dermal immunophenotypic alterations and subsequent development of dermatitis with resultant alopecia.