The Patterns and Causes of Dermatitis in Terrestrial and Semi-Aquatic Mammalian Wildlife

SIMPLE SUMMARY: Dermatitis is recognized to manifest from a variety of causes in humans and animals, but these have never been synthesized for wildlife. We document the causes and investigate the magnitude of skin diseases and disorders which manifest as, and are described as, dermatitis in the published literature. Our aim was to identify the major causal agents in the development of dermatitis, and if certain mammalian wildlife groups or captivity status was a precursor for the development of dermatitis. The most common causes of dermatitis identified were mites, bacteria, and fungus, and were more frequently reported for wildlife species within Carnivora and Artiodactyla. Furthermore, associated with genetic and behavioral variables, some threatened species were more likely to exhibit dermatitis in captivity. This study provides insight into wild mammalian species that may be more susceptible to dermatological diseases and discusses the patterns of causes within wild mammals. ABSTRACT: Causative disease and stress agents which manifest as dermatitis in mammals have varying effects on individual animals, from benign irritation and inflammation, to causing morbidity and even mortality. Bacteria, viruses and ectoparasites are all potential causes of dermatitis, and it can be exacerbated by various environmental, genetic and social factors. Furthermore, it is uncertain whether dermatitis is more likely to manifest in already-vulnerable wildlife species. Here, we systematically review the literature for reports of dermatitis in terrestrial and semi-aquatic wild mammalian species, with the goal of determining the biogeographical scale of dermatitis reports, the causes of dermatitis, and whether manifestation of dermatitis is reported more commonly in certain wildlife species or their captivity status (i.e., free-living, in captivity or in a laboratory). We reveal biases in the reporting of dermatitis by a biogeographic realm, with 55% of cases reported in the Nearctic, and towards particular orders of mammals, namely Artiodactyla and Carnivora. Overall, free-living wildlife is almost twice as likely to be reported as having dermatitis than individuals in captivity and six times more likely than individuals in laboratories, which we interpret as owing to exposure to a broader spectrum of parasites in free-ranging individuals, and potential reporting bias in captive individuals. Notably, dermatitis was reported in 23 threatened species, with some species more likely than others to be reported exhibiting clinical signs of dermatitis resulting from underlying health problems. We also find that threatened species are more likely to be reported as having dermatitis in captivity, particularly outside of their endemic home range. This review highlights diverse patterns of dermatological disease causes in captive and free-ranging wildlife, conditions under which they are more likely to be documented, and the need for cross-disciplinary research to ascertain (and so better manage) the varied causes.