Looking at ways climate change may influence the spread of disease

Bacteria
A new model developed by U of T Scarborough researchers may go a long way in helping to better understand how diseases will be affected by climate change.

Don Campbell

A new model developed by a U of T Scarborough biologist may help researchers better understand how diseases will be affected by climate change.

“Climate change is altering the environment as we know it and it’s also changing the interactions species are having with parasites and pathogens,” says Assistant Professor Péter Molnár from the Department of Biological Sciences and lead author of the research.

“The ultimate goal is to have some predictive capability for how these interactions are changing due to changing temperatures to help manage the spread of disease in humans and animals.”

Currently, only a handful of parasites have been well-studied in regard to temperature change, and a major challenge in creating forecasting models is a lack of reliable data. There are more than 300,000 species of worm parasites in vertebrates alone, notes Molnár, and there are many millions of parasites if you include bacteria, viruses and fungi.

“It’s very hard to collect data on all of these species because you would need millions of researchers working on it. But we still need to have some idea of how climate change will impact those species we have limited data on,” he says.  

The model developed by Molnár and his team attempts to address these data shortcomings by using physiological characteristics from well-known species, like the malaria parasite, and apply them to understudied ones. In order to do that, the model uses something called the Metabolic Theory of Ecology (MTE), which essentially helps define the temperature sensitivities of development, mortality, reproduction and population growth for all organisms using metabolism as the key measurement.

“The reason we use MTE is that it’s broad and overarching and represents all organisms very well. This means we can use it to figure out general patterns and apply them in our prediction models, even for the data insufficient species,” says Molnár, whose research focuses on the ecological impacts of climate change.

Peter Molnar
Molnár's research attempts to understand and predict the ecological impacts of climate change. (Photo by Ken Jones)

Climate change can affect parasites and pathogens in a host of different ways. Rising temperatures and changes in humidity can result in changes to how fast certain ones will grow and how long they can live, not to mention different infection pressures that may be placed on a host.

Climate change also means that parasites and pathogens can spread to new locations. One prime example Molnár points to is the spread of malaria to the East African highlands, where a two degree increase in temperature has made it possible for the parasite to live where it couldn’t before.

“Likewise, a warmer climate in Europe or North America or elsewhere could create suitable conditions for these types of parasites to spread as well,” he says. Molnár adds that past research in his lab has looked at how parasites found in caribou and muskox have expanded their range from the Canadian mainland to the arctic islands, likely the result of rising temperatures.

It wouldn’t make sense to go directly to MTE for species that already have a lot of data associated, like the malaria parasite, notes Molnár. Rather, the model is meant to give some idea of how less-studied parasites or pathogens may be affected by climate change.

Another reason for the study is that the methods researchers use to measure how climate will affect the species they are studying vary widely. This study is meant to guide future research in terms of how to collect the thermal data that are the most important for creating predictive models, and provides a step-by-step guide to help researchers fill the data gaps that are currently preventing accurate predictions for most parasites.

“If we can get some idea of what may happen with climate change you can start to plan for the time when a disease arrives, and this applies to wildlife, cattle, humans, whatever you want to manage,” says Molnár.

“This model isn’t an attempt to say we can predict exactly what will happen, but the ultimate goal is to work our way in that direction.”

The research is published in the Journal of Parasitology and received funding from the Network of Centres for Excellence of Canada and the Natural Sciences and Engineering Research Council of Canada (NSERC).