Levels of parasite infection are influenced by variations in host susceptibility and exposure which in turn are determined by environmental conditions. A major challenge for disease workers is to predict how climate change will influence infection risk. This proposal aims to identify both the role of long-term climate change and seasonal variation in relation to changes in the abundance of parasite species in a community of parasites that inhabit a free living host population. The study is based on a unique long term dataset where rabbits have been sampled every month for 29 years. Details are collected on rabbits demography, parasite community structure and environmental data to test the hypothesis that climate warming has increased level of parasitism in species not regulated by immunity but not in species regulated by immunity. Insights will be integrated into seasonal models of increased complexity to provide a working explanation of how climate affects parasite and host ecology, predict future changes and identify means of making control effective.
This detailed interdisciplinary scientific program has some very important broader impacts for our understanding of disease emergence and persistence. Not only will it provide one of the most comprehensive and insightful descriptions of how climate change can affect parasite community in different ways but will represent an ideal condition for training students in a broad range of lab/field techniques and data analyses and teach them how to operate within a dynamic and productive research team and have an international working experience.
Studies from natural ecosystems have highlighted the general negative consequences of climate-related changes on populations and their habitats, including an augmented risk of infectious diseases. Climate warming has been suggested to augment the risk of infectious disease outbreaks by extending the seasonal window for parasite growth and by increasing parasite transmission. Understanding how this occurs in parasite-host systems is important for appreciating long-term and seasonal changes in the exposure of hosts to infections and to reduce species extinction caused by diseases. This proposal has aimed to examine the role of long-term climate warming and seasonal variation on the infections of gastro-intestinal parasites of rabbits. The parasite community of rabbits is remarkably similar to that in agricultural animals and many wildlife animal species and insights gained from this study can be relevant to a large number of host-parasite systems for which long-term data and detailed field and laboratory experiments are difficult to obtain. We approached our questions using a combination of long term monitoring, field manipulation and laboratory experiments and focused on two common worms of the rabbit. Our ultimate goal was to indentify general rules governing host-parasite interactions in a seasonal environment where climate warming and host characteristics (i.e. age, sex or multiple infections) contribute to the variability in the level of infection observed across years and among individuals. Major findings of our work are: Our laboratory and field experiments showed that seasonal changes in intensity, frequency and duration of daily temperature are important causes of variability in parasite development and availability on the grass. Using long-term data on intensity of these two parasitic infections in rabbits we found that climate warming was associated to higher infections at younger age and this was apparent for the worm species regulated by the host immune response. Variability in host characteristics (age, breeding status, co-infection and immune response) is important in affecting parasite infection rate and the ability to transmit the infection. Both parasites adapt their strategies of infection and transmission based on climatic conditions and host characteristics. Our work demonstrates that parasitic infections of a wild herbivore are strongly affected by climate warming but the mechanism regulating their long term dynamics and survival ultimately depends on how these parasites interact with their hosts. Together, these patterns are providing novel insight into our understanding of how climate change and infectious disease dynamics are interrelated; this is fundamental information necessary for understanding close related host-parasite systems where data are not often available and also for developing alternative measures to control parasitic infections. The interdisciplinary nature of this proposal has offered many opportunities for training students in a rigorous and comprehensive way of thinking driven by fundamental questions on the ecology of parasite infections, species interaction and dynamics. The educational component of this study has been high and consistent throughout the years. Minorities and underrepresented groups have been regularly trained in population ecology, parasitology, immunology and epidemiology. These students have been working on individual projects, honor theses or for research credits. The most motivated undergraduates have co-authored scientific papers and presented their results to national events.
