A new research paper finds that alternate patterns of temperature variation bring about very different disease outcomes at different mean temperatures. In other words, the area within the world that an infection occurs and the climatic patterns will lead to different virulence factors and potentially different outcomes and possibly adaptation of different treatment regimes.
The core of the research study shows that temperature variation affects pathogens and their hosts in distinct ways. Furthermore, the study shows that invasive organisms are influenced by the type of variation and the average background temperature that the pathogen is subjected to.
What is of additional importance is the current epoch – the Anthropocene. Here climate change and extreme weather ae observed as having complex effects on disease transmission.
To derive at these conclusions, the researchers looked at the effects of different temperatures on various traits in a host organism. This involved a small crustacean called Daphnia magna together with the known gut parasite, Odospora colligata. Since transmission of the parasite is equivalent to common mechanisms of environmental transmission, as would be the case with the SARS-CoV-2 virus (responsible for COVID-19) and the bacterial disease cholera, te modelling was strong applicable to many disease vector situations.
The examination found organisms respond differently across three distinct temperature regimes: a constant temperature, and two variable regimes. The variables were: with daily fluctuations of either 3°C above or below the norm and three-day heatwaves of 6°C above ambient temperature.
The crustacean’s lifespan and infection status was assessed according to each condition. The data was subject to computer modelling. The analysis found that daily fluctuations of temperature reduced the infectivity and spore burden of the parasite compared to those kept at the constant average temperature.
However, it was of concern that the number of spores in the crustacean host increased following the three-day ‘heatwave’. This indicates that rises in global temperature may see increased transmission of diseases.
According to lead researcher Pepijn Luijckx, William C. Campbell Lecturer in Parasite Biology, Trinity College Dublin, Ireland: “Climate change is predicted to increase not only average temperatures but also temperature fluctuations and the frequency and intensity of extreme weather events.”
Luijckx adds: “Yet 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.”
The research should trigger the need for a new area of scientific inquiry – understanding the mechanisms behind species interactions in fluctuating environments.
The research appears in the journal eLife, titled “Alternate patterns of temperature variation bring about very different disease outcomes at different mean temperatures.”
