TCD study suggests global heating could have unpredictable disease effects

15 Feb 2022

The water flea called Daphnia Magna. Image: Per Harald Olsen/NTNU via Flickr

Research suggests that in certain cases, parasites can handle sudden temperature changes better than their hosts.

Research at Trinity College Dublin suggests that temperature variation can have very different effects on infection rates and disease outcomes depending on the average background temperature.

This indicates that global temperature changes from the climate emergency could have unpredictable impacts on disease transmission.

The study published in science journal eLife looked at the effects of different temperatures on various traits in a host organism – a small water flea called Daphnia magna – and a common gut parasite it deals with called Odospora colligata.

The team noted that the climate emergency is predicted to not only increase average temperatures, but also increase temperature fluctuations and extreme weather events.

“Although studies have quantified the effects of rising average temperatures on host and pathogen traits, the influence of variable temperature regimes such as heatwaves remains largely unknown,” said Dr Pepijn Luijckx, co-first author of the study and William C Campbell professor in parasite biology at Trinity.

The team looked at how the organisms responded to differences in average temperature, with daily fluctuations of a few degrees Celsius and three-day heatwaves with a six degree Celsius increase. They then took measurements of the water flea’s lifespan, fertility, infection status and the number of parasite spores within its gut.

The research found that daily fluctuations of temperature reduced infection rates and parasite spore numbers in the water flea compared to those kept at a constant average temperature. However, the infectivity of the parasites after a heatwave was almost the same as the parasites maintained at a constant temperature.

The fitness and reproductive success of the water fleas was generally reduced when exposed to either the parasite spores or when experiencing variable temperatures. This suggests that under certain circumstances, the parasite was able to withstand the sudden temperature changes better than the host.

The number of spores in the water fleas increased following the three-day heatwave when the background constant temperature was at 16 degrees Celsius, but the spore burden was reduced at higher temperatures.

“Our findings show that temperature variation alters the outcome of host-pathogen interactions in complex ways,” Luijckx said. “Not only does temperature variation affect different host and pathogen traits in a distinct way, but the type of variation and the average temperature to which it is applied also matter.

“This means that changing patterns of climate variation, superimposed on shifts in mean temperatures due to global warming, may have profound and unanticipated effects on disease dynamics,” Luijckx added.

Luijckx worked on the research with Charlotte Kunze, Andrew Jackson and Ian Donohue. Funding for the study was provided by Science Foundation Ireland and the Irish Research Council.

The water flea called Daphnia magna. Image: Per Harald Olsen/NTNU via Flickr (CC by 2.0)

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Leigh Mc Gowran is a journalist with Silicon Republic