Interspecific parasite transmission is one of the main risks associated with interactions between wild and domestic animal species, and it can give place to emerging diseases and epidemics. These processes have been studied mostly in the light of human importance, as they pose a threat for livestock health. However, much less attention has been given to the effects on wildlife. Here, we analyze the transmission of Ancylostoma, an environmentally transmitted intestinal helminth, between wild ocelots (Leopardus pardalis) and domestic dogs in the Osa peninsula, Costa Rica, and determine how different host species contribute to the persistence of the parasite in the system.
To estimate parasite prevalence in each species, we collected scat samples, isolated helminth eggs from them using a floatation method and identified the eggs using light microscopy. We identified individual animals from camera-trap photographs and estimated each species abundance using a spatially explicit capture-recapture model. To estimate spatial overlap, we calculated the ratio of sites with presence of both species to the total of sites with presence of each species. We used these data, and species-specific egg shedding rates obtained from the literature to quantify the relative contribution of each host species. For this, we used an epidemiological model for multiple hosts with environmentally transmitted parasites. The model allows estimating species-specific R0, the mean number of secondary infections each host produces.
Results/Conclusions
The model estimated a partial R0 of 0.80 for ocelots, 1.54 for dogs, and a combined R0 of 1.92. These results show that dogs would be acting as reservoir hosts, and the parasite spills over to wild ocelots. Furthermore, sensitivity analyses showed that only for a few combinations of parameter values the parasite could be sustained by either host species independently.
Our results suggest that the presence of the parasite in wild hosts could be a direct consequence of interaction with humans, despite the low density of settlements in the area. While this helminth is not thought to have a significant effect on population viability, other disease-causing parasites have similar modes of transmission. Therefore, our methods and results can be used to design management strategies for a range of potential diseases arising from proximity and interaction with humans.