University of Calgary

Ecologists warn of growing link between climate change, spread of disease

UToday HomeAugust 2, 2013

Muskoxen, well adapted to cold Arctic environments.Muskoxen, well adapted to cold Arctic environments, may be particularly susceptible to rapid climate change and emerging infectious diseases, with recent mortality attributed to the climate-facilitated emergence of protostrongylid lungworms in the Arctic archipelago. Photo by Susan KutzClimate change is already affecting the spread of infectious diseases worldwide, with serious impacts to human health and biodiversity conservation, warns an international team of leading disease ecologists.

Writing in the journal Science, the team — including Susan Kutz, associate professor in the Faculty of Veterinary Medicine — proposes that modeling the way disease systems respond to climate variables could help public health officials and environmental managers predict and mitigate the spread of lethal diseases.

As the link between climate change and disease becomes clearer, one of the most vulnerable regions on the planet is the Arctic, says Kutz, also a regional director with the Canadian Co-operative Wildlife Health Centre. “The Arctic is like a ‘canary in the global coal mine,’ ” she says.

“Climate warming in the Arctic is occurring more rapidly than elsewhere, threatening the health and sustainability of Arctic plants and animals, which are adapted to a harsh and highly seasonal environment and are vulnerable to invasions by ‘southern’ species — both animals and parasites.”

Issue a growing concern

The issue of climate change and disease has provoked intense debate over the past decade, particularly in the case of diseases that affect humans.

Climate warming is already causing changes in diseases affecting wildlife and agricultural ecosystems. “In many cases, we’re seeing an increase in disease and parasitism,” says lead author Sonia Altizer of the University of Georgia Odum School of Ecology. “But the impact of climate change on these disease relationships depends on the physiology of the organisms involved, the location on the globe, and the structure of ecological communities.”

“For a lot of human diseases, responses to climate change depend on the wealth of nations, healthcare infrastructure, and the ability to take mitigating measures against disease. The climate signal, in many cases, is hard to tease apart from other factors like vector control and vaccine and drug availability.”

At the organism level, climate change can alter the physiology of both hosts and parasites. Some of the clearest examples are found in the Arctic, where temperatures are rising rapidly, resulting in faster developing parasites. A lungworm that affects muskoxen, for instance, can now be transmitted over a longer period each summer, making it a serious problem for the populations it infects.

Link between biodiversity loss and climate change

Climate change is also affecting entire plant and animal communities. This is particularly evident in tropical marine environments such as the world’s coral reef ecosystems. In places like the Caribbean, warmer water temperatures have stressed corals and facilitated infections by pathogenic fungi and bacteria. When corals, the framework builders of the ecosystem, succumb, the myriad of species that depend on them are also at risk.

“Biodiversity loss is a well-established consequence of climate change,” said coauthor Richard Ostfeld of the Cary Institute of Ecosystem Studies. “In a number of infectious disease systems, such as Lyme disease and West Nile virus, biodiversity loss is tied to greater pathogen transmission and increased human risk. Moving forward, we need models that are sensitive to both direct and indirect effects of climate change on infectious disease.”

Call for a comprehensive approach

“Earth’s changing climate and the global spread of infectious diseases are threatening human health, agriculture and wildlife,” says Sam Scheiner, National Science Foundation program director for the joint NSF-National Institutes of Health Ecology and Evolution of Infectious Diseases Program, which funded the research. “Solving these problems requires a comprehensive approach that unites scientists from biology, the geosciences and the social sciences.”

Adds Ostfeld, “We need to transcend simple arguments about which is more important — climate change or socioeconomics — and ask just how much harder will it be to control diseases as the climate warms? Will it be possible at all in developing countries?”

Use data to create early warning system

To respond to that challenge, Altizer and her colleagues — Kutz, Ostfeld, Pieter Johnson of the University of Colorado, Boulder, and Drew Harvell of Cornell University — lay out an agenda for future research and action in their review, “Climate change and infectious diseases: From evidence to a predictive framework.”

One recommendation is to expand data about the physiological responses that hosts and parasites have to temperature changes to help develop early warning systems. “We’d like to be able to predict, for example, that if the climate warms by a certain amount, then in a particular host-parasite system we might see an increase from one to two transmission cycles per year,” Altizer says. “But we’d also like to try to tie these predictions to actions that might be taken.”

Such forecasting is well established in crop disease management, and has been used to preventatively close coral reefs and target areas at risk of malaria outbreaks.


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