Impact of human-animal interactions in highly anthropised environments : an "Urban One Health" approach based on the example of the European hedgehog (Erinaceus europaeus)

This doctoral thesis, the outcome of a bi-disciplinary path and collaboration between ecology and wildlife veterinary medicine of non-captive species, aimed to explore the concept of “One Health” using the European hedgehog (Erinaceus europaeus) as a model. This concept highlights the interconnections between environmental health, animal health, and human health. To carry out this study, I sampled 133 hedgehogs admitted to the Wildlife rescue hospital at the National Veterinary School of Alfort (CHUV-FS, ENVA). The hedgehog is an urban species. The “health” of its environment can therefore be assessed through three factors: urbanisation, pollution, and anthropisation. Within this framework, I investigated the impact of urbanisation and trace element contamination on hedgehog health and melanin-based colouration. I also examined the effects of hospitalisation in wildlife rescue centres—considered a strongly anthropised environment—on health and physiological stress in this species. To link animal and human health, special attention was given to zoonotic infectious agents. We explored a broad panel of pathogens transmitted by arthropods and blood parasites (Anaplasma spp., Babesia spp., Rickettsia spp., Bartonella spp., etc.) in relation to urbanisation. I then focused on the presence of ticks and Trichophyton erinacei, as well as the seroprevalence of Borrelia burgdorferi s.l. and Leptospira spp., in relation to hospitalisation. Three main correlations emerged from our study of the effect of urbanisation: the first concerned contamination by trace elements, the second certain infectious agents, and the third variation in melanin-based colouration. We highlighted a significant contamination of hedgehogs by trace elements in the Île-de-France region. Human density was associated with internal concentrations of lead, copper, and nickel in organs, while the proportion of built-up area was correlated with levels of lead and zinc in spines. The hedgehog thus appears to be a relevant bioindicator for these elements. Regarding infectious agents, two could be linked to urbanisation: Anaplasma phagocytophilum (showing high prevalence in hedgehogs) and Leptospira spp. Finally, our results revealed a trend towards lightening of hedgehog colouration along the urban gradient. Several hypotheses may explain this result, such as camouflage, thermoregulation related to urban heat islands, or selective pressure from road collisions. We then sought to understand the consequences of trace element contamination on hedgehog health in interaction with melanin-based colouration. Negative effects of cadmium, even at environmental exposure, were demonstrated through an increase in Trichophyton carriage. Selenium, in interaction with melanin-based colouration, also appeared to be involved in the dynamics of ticks and Trichophyton, although no clear explanation for these results could be established. These observations open the discussion on an evolutionary interpretation of melanin-based colour variation as a response to trace elements in this species. Finally, the most striking results concern the study of hospitalisation in hedgehogs. Care provided in rescue centres improved animal health, notably through the resolution of lesions caused by Trichophyton or trauma. However, this study also reported persistent respiratory signs after hospitalisation. Notably, hospitalisation significantly decreased cortisol levels and reactive oxygen metabolites in the blood, and no detectable effect of hospitalisation was observed on the seroprevalence of Borrelia and Leptospira. Overall, this work provides a concrete illustration of the One Health approach. It brings new knowledge on the impact of both humans and the environment on this declining species, while also helping to put into perspective the potential risks it may represent for human health.