Scientists analysed infection risk in four natural populations of field voles
The findings of the work could help with the future prediction and control of parasitic diseases in animals. The results could also help further understanding of infection in people.
Scientists analysed infection risk in four natural populations of field voles over a five-year period, studying a community of four microparasites consisting of cowpox virus, Babesia microti, Bartonella spp. and Anaplasma phagocytophilum.
Previously interactions between parasites in natural populations had been studied only rarely. It is likely, however, that most hosts, including humans, at most periods, are infected with more than one parasite species, either simultaneously or sequentially.
The research team investigated if there was a structure to parasite communities and if there was a pattern of co-infection. They also explored how parasites might affect one another and how significant these effects could be.
Analysis of the time-series data generated from the field study showed that the community of parasites represented not four independent infections but an interconnected web of interactions. The study also showed that there are large positive and negative effects of other infections on the risk of being infected by any given pathogen. Effects are typically of greater magnitude, and explain more variation in infection risk, than the effects more commonly considered in disease studies, such as age, sex or season.
Professor Mike Begon, from the Institute of Integrative Biology at the University of Liverpool, said: “The main surprise was the strength of these interactions. We’ve known for a long time that individuals become more or less susceptible at different times of year, for example, but to find that interactions between pathogens can have as big an effect was unexpected.”
Dr Steve Paterson, also from the Institute of Integrative Biology, said: “We hope that our work will help stimulate similar work in humans, where, particularly in Africa, infections with multiple pathogens are the norm.”
The study highlights the dangers inherent in the common practice of considering parasite species in isolation rather than looking at whole parasite communities.
The research, in collaboration with the University of Aberdeen and the UK’s Centre for Ecology & Hydrology (CEH), is published in Science and was funded by the National Environment Research Council (NERC) and the Wellcome Trust.
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