The role of wild carnivore carcasses in the transmission of infectious agentsepidemiological and ecological aspects

Abstract

Esta t This PhD dissertation has delved into the epidemiological consequences of interactions between wildlife and mammalian carnivore carcasses in three mountainous areas of southeastern Spain. Moreover, the degree of interdisciplinarity, the use of ecological terminology and the arguments supporting the trophic transmission of pathogens in studies at the wildlife-livestock-human interface have been evaluated. In Chapter 1 we conducted a systematic review to address the current state of knowledge about parasite transmission by meat consumption at the wildlife-livestock-human interface. Also, we evaluated the degree of interdisciplinarity of the research teams and the accuracy in the use of ecological terms, just as the scientific reliability of arguments used to support the epidemiological conclusions. Most of the articles justified the trophic transmission of parasites using exclusively bibliographic references or non-science-based assertions. Besides, ecological terms in many publications were absent and, when mentioned, were mainly inaccurate or misused. This lack of precision and rigor may be due because scientific publications are mostly carried out by unidisciplinary research teams. These results highlight the need to establish collaborations between researchers trained in Ecology and Epidemiology in epidemiological studies at the wildlife-livestock-human interface. In Chapter 2 and 3 we investigated the behavior of vertebrates at carnivore carcasses, with special focus on interaction between red fox (Vulpes vulpes) and conspecific carrion for the transmission of meat-borne and non-trophically transmitted parasites. For this, 56 fox carcasses and 10 carcasses of other mesocarnivore species were monitored for 7-10 weeks using camera traps in three mountainous areas of southeastern Spain, with different community of vertebrates and degrees of anthropization. Foxes were very efficient in detecting mesocarnivore carrion. Notwithstanding, the widespread behavior consisted of avoiding consumption or delaying it several weeks, especially at conspecific carcasses. Scavenger species contacted more frequently with carcasses than non-scavengers, probably as a result of their scavenging habits. Regarding fox, contact occurred more frequently and earlier at heterospecific carcasses, being delayed several weeks at fox carcasses. In relation to rubbing, a similar pattern was observed for both type of carrion, although its frequency was greater at conspecific carcasses. Instead, marking behavior was most frequently recorded at fox carcasses, probably because they are used as information points of longer persistence. Our results suggest that the decision to consume conspecific carrion is probably conditioned by two contrasting forces: the high nutritional value of conspecifics and the risk of acquiring shared parasites. We demonstrate that carnivore carrion is a fundamental component in the "landscape of disgust" of carnivores. Related to non-trophic interactions, foxes avoided the early contact with carrion, probably to reduce the risk of infection by non-trophically transmitted parasites, especially in conspecific carcasses. However, close contact caused by rubbing could play an important role in the transmission of ectoparasites. Marking events also may pose an epidemiological risk in carcass sites, since pathogens excreted by urine and feces could be present on the carcass or its vicinities for a long time. Consequently, the fox' strategy to reduce the risk of infection seems ineffective for some non-trophically transmitted parasites. In general, this doctoral thesis provides a detailed knowledge about the ecological interactions between carnivore carrion and vertebrate wildlife. This information is a fundamental basis for inferring the epidemiological consequences derived from these relationships. Moreover, we encourage the increase of interdisciplinary collaboration in epidemiological studies at the wildlife-livestock-human interface from a One Health perspective.