Too hot to hold: climate change could reshape the map for a wild parasite

Climate change is projected to alter the biology and distribution of many helminth species. We investigated the influence of climate on the current distribution of Parapharyngodon sceleratus, a monoxenic, generalist nematode parasite infecting 29 lizard species in South America, and evaluated its potential future range shifts under climate change. Using ecological niche modelling, we predicted the species' current and future range distributions. Precipitation-related variables were the primary determinants of the spatial distribution of the worm. Areas of medium to high environmental suitability are concentrated in regions with seasonal tropical warm climates, as well as temperate regions with dry summers and mild winters. Future projections indicate a progressive reduction of highly suitable areas and an expansion of areas with low suitability, particularly in northern and central South America, by 2100. However, the Atlantic Forest, the northeastern Brazilian coast, a site within the semiarid Caatinga, and open vegetation areas in Chile persist as refugia of high habitat suitability. Our findings suggest that rising temperatures and altered precipitation patterns may constrict the geographic range of this helminth. Contrary to predictions for other parasite taxa, our results highlight a negative impact of climate change on the distribution of a monoxenic helminth.