Are you as tough as a parasite?
Maybe you’re not. According to research done on water fleas, infectious disease parasites may be better able to cope with unpredictable climate change than their hosts.
An unpredictable set of complications may follow in the wake of accelerating climate change, already an unpredictable phenomenon, as event chains caused by fluctuating temperatures create dynamic responses in natural systems.
Researchers at Trinity College (Dublin, Ireland) examined the effects of temperature variation on infections in Daphnia magna, a species of water flea, and its gut parasite, Ordospora colligata. They used one constant temperature regime and two variable temperature regimes, fluctuating 3°C in either direction, in addition to 3-day heatwaves of 6°C above normal. They examined the effects on D. magna’s lifespan, fertility, infection status and parasite spore count, outputting the data into a statistical model for analysis of the three separate temperate regimes.
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The results, published in eLife, indicated that the parasite tolerated the temperature fluctuations better than its water flea host. While daily fluctuations reduced by 5°C, the upper bounds at which O. colligata infectivity was successful in comparison with consistent temperatures, the effects of heatwaves on the parasite were interesting. After a heatwave, disease infectivity was more-or-less unchanged in comparison to constant-temperature conditions. In addition, following the 3-day heatwave events, spore count in water fleas increased when the ambient temperature was maintained at 16°C. This dropped at higher temperatures. By contrast, the host’s fitness and reproductive success suffered in conjunction with spore exposure or variable temperatures.
This in turn seems to imply that the increasing prevalence of rising temperatures and extreme weather events provoked by climate change presages erratic consequences on host-pathogen interactions. The study suggests that the variation in temperature has equally variable effects relating to the ambient temperature and optimum environmental temperature for the parasite.
Co-first author Pepijn Luijckx summarized: “Our findings show that temperature variation alters the outcome of host-pathogen interactions in complex ways. 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.”
Their study puts yet more emphasis on the planet’s ecological interconnectivity, highlighting the destabilizing effects of climate change across complex global networks of interdependent systems. An increasing amount of research seems to indicate that it is not possible to impact one system in isolation, with the knock-on effects manifested in one system chaining to its connected systems.
