Host immunity alters climate change impact on the dynamics of helminth infections
Global climate change is predicted to alter the distribution and dynamics of soil-transmitted helminth infections. However, outcomes might not match the projected impact given that host immunity could alter the effect of climate on host-parasite interactions. We used data on the abundance of two helminth species from a rabbit population sampled monthly over 26 years in Scotland -where evidence of temperature warming and increased humidity has been recorded during the study period- and developed a helminth-host mathematical model that explicitly addressed the role of host immunity on the intensity of infection and temperature/relative humidity on the availability of free-living stage on the herbage. Climate-immunity processes were examined at the seasonal, decadal and long-term scale.
We provide evidence that climate warming increases the availability of both helminth species on the herbage and the proportional increase in the intensity of infection for the helminth not regulated by immunity. In contrast, there was no significant long-term positive trend for the immune-controlled helminth, since immunity reduced the net outcome of climate on parasite dynamics. Even so, hosts experienced higher infections at an earlier age during critical months. Immunity can alleviate the expected impact of climate on parasite infections over the years but can also shift the seasonal peak of infection towards the younger individuals.