Interaction between the red fox (Vulpes vulpes), helminths and environmental characteristics in semi-arid areas of southeastern Iberian Peninsula

Laburpena

The study of the cardiopulmonary, gastrointestinal and urinary nematode communities of the red fox (Vulpes vulpes) in semi-arid Mediterranean areas, specifically in the Region of Murcia (SE Spain) was described in this Thesis. Considering the characteristic aridity of this region, water stress can be a determinant for the approach of fox populations towards anthropized areas, generating higher contact rates at the wild-domestic-human interface. Therefore, the influence of biotic and abiotic variables on the abundance of these parasite communities was analysed. In this sense, obtaining reliable prevalence and intensity data is essential for this kind of epidemiological studies. For this reason, the sensitivity and accuracy of the post-mortem diagnostic method for cardiopulmonary nematodes was evaluated in Chapter 1. To the traditional methodology, consisting in opening the tracheobronchial tree and the cardiac cavity, two consecutive steps were added: squeezing and artificial digestion of the lung parenchyma. Our results indicated that this procedure is more sensitive and accurate in the estimation of parasite intensity than the traditional one. Moreover, in the case of nematode species located in small capillaries or bronchioles, the use of artificial digestion facilitates the detection of parasitized foxes, decreasing the false negative rate. Chapter 2 described the nematode communities of the cardiopulmonary and gastrointestinal systems of 167 foxes. The total richness was eleven nematode species, seven in the gastrointestinal (Pterygodermatites affinis, Uncinaria stenocephala, Toxocara canis, Toxascaris leonina, Spirocerca vulpis, Oxynema crassispiculum and Trichuris vulpis) and four in the cardiopulmonary system (Angiostrongylus vasorum, Crenosoma vulpis, Eucoleus aerophilus and Metathelazia capsulata). The influence of biotic and environmental variables on the abundance of A. vasorum, C. vulpis, U. stenocephala, T. canis and T. leonina was evaluated, taking into account their sanitary health importance for domestic canids and, in some cases, because they are zoonoses. The results revealed the importance of humidity and temperature in this type of environment, since they highly influence the survival and development of the free-living infective stages of these parasites, or of the intermediate or paratenic hosts necessary for these life cycles. Additionally, forestry or agricultural areas had a significant influence on abundance, as they allow the maintenance of favourable conditions of moisture and temperature. On the other hand, the presence of species with zoonotic potential in the study area suggests the importance of establishing epidemiological vigilance and pathogen control plans, due to the existence of shared areas between wild and domestic canids, which could lead to the transmission of these parasites at the wild-domestic-human interface. Similary, environmental factors showed the most significant influenced on the abundance of Pearsonema plica (Chapter 3), a nematode detected when the urinary system (bladder, kidneys and ureters) of the 167 foxes was analysed. Despite the aridity of the study area, the finding of this nematode evidences that places with suitable humidity conditions for the development of the parasite’s life cycle also exist in these areas. Finally, in Chapter 4, the morphometric and molecular description of the bronchopulmonary nematode M. capsulata, a spirurid previously described in bronchi and bronchioles of other carnivore species, was performed. This is the first description of this species in European foxes, being also the first study where the molecular markers of this nematode species are reported. This information may be very useful for future phylogenetic studies of the genus Metathelazia spp. or the family Pneumospiruridae.