Epidemiological factors of Eucoleus aerophilus infection in red foxes (Vulpes vulpes) from semi-arid Mediterranean environments

Eucoleus aerophilus is a ubiquitous zoonotic nematode found in the tracheobronchial mucosa of the definitive hosts, described in wild and domestic canids, including the red fox ( Vulpes vulpes ). To assess E. aerophilus occurrence and intensity in red foxes, the respiratory system of 126 foxes from Region of Murcia (SE, Spain) were examined. Statistical analyses were performed to investigate the influence of biotic and abiotic factors on the parasite's occurrence. The occurrence of E. aerophilus was 28.6% (95% CI: 20.6–36.4), with a mean intensity of 3.1 nematodes per parasitised fox. The infection rate and parasite intensity were higher in forested areas, suggesting that earthworm abundance and a longer survival of infective E. aerophilus eggs increase the risk of transmission and maintenance in the environment. Moreover, an inverse relationship between E. aerophilus occurrence and temperature ( p < 0.05) was observed. Results demonstrated that foxes participate in maintaining the cycle of E. aerophilus in semi-arid Mediterranean environments. This should be taken into account at the wild-domestic-human interface. The development of a predictive model of E. aerophilus infection risk in red foxes will allow the design of future strategies for the prevention of capillariosis, especially in areas where contact between foxes, domestic carnivores, and humans exists. • E. aerophilus prevalence reached 28.6% in red foxes from south-eastern Spain • Forested habitats showed higher infection intensity and potential egg persistence • Cooler temperatures increase parasite occurrence, revealing environmental constraints • Red foxes act as key reservoirs, sustaining E. aerophilus in semi-arid ecosystems