A tale of two nematodes: Climate mediates mustelid infection by nematodes across the geographical range

Abstract

Parasites have the potential to negatively affect host populations, if infection intensity is high. For parasites in which part of life cycle takes place outside the host, host infection intensity is likely affected by climate condition. Therefore, the parasite's impact on the host populations could be related to climatic conditions and may be altered with climate change. The aim of our study was to analyse the prevalence and infection intensity of two nematodes (Aonchotheca putorii and Molineus patens) from the Northern Hemisphere in relation to variations in climatic conditions. We reviewed 54 published studies on the occurrence of these two nematode species in 7 mustelid hosts. For A. putorii, infection parameters were higher when the stomach was included in the analyses compared to M. patens. The seasonality of precipitation influenced the prevalence the most, and the mean temperature of the warmest quarter had the strongest influence on infection intensity. The predicted prevalence of M. patens increased with increasing seasonal variation in precipitation, while the prevalence of A. putorii decreased. The predicted infection intensity of M. patens decreased with increasing precipitation seasonality, whereas the intensity of A. putorii infection did not change much. A. putorii infection intensity significantly decreased with increasing mean temperature of the warmest quarter, while the infection intensity of M. patens was not significantly related to this variable. Prevalence and infection intensity varied over the geographic range for both parasites, broadly with higher levels in northern latitudes for A. putorii and in southern latitudes for M. patens. Our study highlights the differences between these two nematode species and shows that the severity of host infection by these parasites is complex and mediated by climatic conditions. The results suggest that current climate change may potentially modify susceptibility and exposure to parasitic infections in mustelids.

Keywords: Aonchotheca putorii; Climate mediate interaction; Geographic variation; Host-parasite; Molineus patens; Parasite prevalence.

Graphical abstract

Fig. 1

Geographical location of study sites for the nematode parasites Aonchotheca putorii and Molineus patens, within the Palaearctic and Nearctic in seven mustelid host species. Details of the samples are given in Table S1.

Fig. 2

Model results for Aonchotheca putorii and Molineus patens infection parameters in seven mustelid species. Panels show model-averaged predictions of prevalence and infection intensity depending on the part of the alimentary tract analysed and climatic conditions (seasonality in precipitation and mean temperature of the warmest quarter). Points and lines show the mean, whiskers or shading denote 95% confidence intervals. Remaining explanatory variables were kept at their mean values or most common factor levels. The distribution of the data is shown at the bottom axes as a histogram or density plots.

Fig. 3

Prediction of prevalence and infection intensity of Aonchotheca putorii and Molineus patens in the Northern Hemisphere based on averaged model estimates, using the WorldClim climate data set. Areas outside of the range of climatic variables used for model fitting are filled with checkerboard pattern. Transparency of the prediction colour reflects the coefficient of variation (CV) of predicted values (i.e. more uncertain prediction has more pattern tint). Predictions assumed the stomach was included in the analyses. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)