The ongoing increase in human activities and settlements near natural habitats increases interaction rates between humans, wildlife and domestic animals, thus also increasing the potential for parasite spillover and emerging diseases. While there is growing awareness of the risk that parasites of domestic species represent for wildlife and vice versa, understanding and managing these risks represents a significant challenge, particularly in highly biodiverse areas with many interspecific interactions. We analyzed the risk for parasite spillover among wild and domestic species in the Osa region, Costa Rica. We used a large-scale, collaborative camera-trap network and joint species distribution models to characterize the distribution of wild mammals in relation to anthropogenic disturbance, and to identify which species have the greatest potential for interaction with domestic species. Following this analysis, we analyzed the risk for transmission of strongyles, a common group of parasitic nematodes transmitted environmentally, among domestic dogs and wild felines. We collected scat from dogs, ocelots (Leopardus pardalis) and pumas (Puma concolor) and used parasitological methods and molecular analyses to detect and identify helminth parasites. Finally, we used the estimations of parasite prevalence, species abundance, and overlap to develop a mathematical model of the risk of spillover, under different scenarios.
Mesopredators like ocelots and pumas showed no response to disturbance, which creates significant risk of interaction with humans and domestic species, especially considering their wide distribution. We found high prevalence ( >70%, 95% CI: 67.0-80.7%) of hookworms (Ancylostoma spp.) in domestic dogs. Based on these values and our model, we would expect a prevalence of 5% in ocelots, the more abundant of the two felids. The observed strongyle positivity rate in ocelots was four times higher than this prediction, making it unlikely that the parasite species in felines was the same as in dogs. Molecular analyses were also unable to confirm if wild and domestic hosts are sharing strongyle parasites, possibly due to low DNA quality from fecal samples. According to our model, low compatibility between host and parasite greatly limits the prevalence that could be reached in wildlife, even though higher overlap could increase the likelihood of parasite spillover. The combination of wildlife/domestic animal monitoring, parasitology, molecular diagnostics and mathematical modelling enabled us to overcome significant logistical challenges and draw inferences about host-parasite dynamics, and estimate parasite spillover risks. Similar approaches could complement wildlife disease monitoring programs worldwide to shed light on understudied helminth-host dynamics at the domestic-wild interface.