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As climate change worsens, ecosystems are becoming more stressed due to rising temperatures, shifting weather patterns and extreme events like floods and droughts. When these stressors are combined with plastic pollutants, organisms can become more vulnerable, potentially altering how infectious diseases spread in wildlife and humans.

While a growing body of research has focused on how plastics affect marine life, the link between plastics and infectious disease dynamics is less understood. To address this knowledge gap, chemistry and biology professor Janet Koprivnikar and master鈥檚 student Mary K. C. Balsdon studied how microbeads 鈥� tiny pieces of plastic debris from the disposal and breakdown of consumer products and industrial waste 鈥� influence host-parasite interactions in aquatic environments. 

鈥淩esearch has typically focused on how pollutants impair a host鈥檚 ability to resist or tolerate infections,鈥� said professor Koprivnikar. Her team鈥檚 study went further, exploring how microbead exposure may also affect infectious parasites in the environment. This research offers valuable insights into the broader ecological implications of environmental pollution.

Plastic pollution and disease dynamics

As outlined in their recent paper published in Oecologia, the researchers found that microbeads could unexpectedly increase the production of parasite stages in infected hosts, making them 鈥榮uper-spreaders鈥� in effect. This result raises concerns about disease outbreaks worsening if organisms pass more infectious stages into the environment as a result of plastic ingestion.

鈥淥ur findings were startling,鈥� professor Koprivnikar said, referring to the team鈥檚 unexpected observation that the exposure of parasite-infected snails (hosts) to diets containing plastic microbeads had a significant effect on the production of more infectious stages but minimal impact on host growth and survival.

This result complicates the usual understanding of contaminants, which are often expected to stress organisms, reduce their health and decrease their ability to support parasite development. Since infectious disease dynamics are complex and involve multiple factors, including exposure and host susceptibility, this research emphasizes the importance of considering environmental pollutants as potential contributors to disease outbreaks.

Implications of climate change on infectious diseases

Professor Koprivnikar notes that interactions between pollutants and disease may intensify when environmental stressors from climate change are added to the mix. 鈥淥ne stressor on its own may not be catastrophic, but when combined with others 鈥� like parasitic infections 鈥� the results can tip an organism's ability to cope with environmental changes.鈥�

Her research findings underscore the need for a comprehensive climate action approach that considers how various factors interact, such as climate change, pollution and disease. 鈥淲e need to start studying these stressors in a more holistic way,鈥� she urges, emphasizing that addressing one environmental issue at a time, such as plastic pollution or infectious disease, is insufficient in the face of interconnected global challenges.

Professor Koprivnikar advocates for a 鈥減recautionary principle鈥� approach 鈥� taking measures to reduce plastic pollution and other environmental contaminants before their full impacts on ecosystems and public health are known. 鈥淯ntil we have strong evidence that these contaminants won鈥檛 make infectious disease dynamics worse, we should be cautious about adding more plastic to the environment,鈥� she advises.

One stressor on its own may not be catastrophic, but when combined with others 鈥� like parasitic infections 鈥� the results can tip an organism's ability to cope with environmental changes.

The research described in this article is supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the 成人大片 Faculty of Science Discovery Accelerator program.