Global warming likely to raise disease risk for animals

Changes in climate can increase infectious disease risk in animals, with the possibility that these diseases could spread to humans, warn researchers.

The study, published in the journal Science, supports a phenomenon known as “thermal mismatch hypothesis,” which is the idea that the greatest risk for infectious disease in cold climate-adapted animals — such as polar bears — occurs as temperatures rise.

The hypothesis proposes that smaller organisms like pathogens function across a wider range of temperatures than larger organisms, such as hosts or animals.

“Understanding how the spread, severity and distribution of animal infectious diseases could change in the future has reached a new level of importance as a result of the global pandemic caused by SARS-CoV-2, a pathogen which appears to have originated from wildlife,” said study co-author Jason Rohr from the University of Notre Dame in the US.

“Given that the majority of emerging infectious disease events have a wildlife origin, this is yet another reason to implement mitigation strategies to reduce climate change,” Rohr added.

The research team collected data from more than 7,000 surveys of different animal host-parasite systems across all seven continents to provide a diverse representation of animals and their pathogens in both aquatic and terrestrial environments.

The study showed that pathogens found at warm locations outperform their animal hosts during cool weather as warm-adapted animals perform poorly.

Similarly, pathogens found at cool locations thrive at warm temperatures, while cold-adapted animals are less tolerant of the heat.

Researchers also collected historical temperature and precipitation records at the time and location of each survey, and long-term climate data for each location to understand how temperature affected animal disease risk in different climates, and how these patterns varied depending on traits of animals and pathogens.

The study also revealed that cold-blooded animals tended to offer stronger support for the thermal mismatch hypothesis than warm-blooded animals.

Next, they coupled their models to global climate change projections to predict where the risk of animal infectious diseases might change the most.

The analysis suggests that global warming will likely shift infectious disease away from the equator, with decreases of animal infectious diseases in the lowland tropics and increases in the highland tropics, temperate and cooler regions of the planet.