April 14, 2015

Climate Change and Brain-Eating Parasites

Joe Romm of Climate Progress details the impact of climate change on global health:

It’s a myth there are no big winners from climate change besides fossil fuel companies.

According to one study, global warming is doubling bark beetle mating, triggering up to 60 times as many beetles attacking trees every year. The decline in creatures with shells thanks to ocean acidification “could trigger an explosion in jellyfish populations.” And climate change has helped dengue fever, which spread to 28 U.S. states back in 2009.

Of course, invasive plants will become “even more dominant in the landscape.” And who doesn’t love ratsnakes?

Let’s also not forget brain-eating parasites, which are expected to thrive as U.S. lakes heat up. That parasite — the amoeba, Naegleria fowleri — feasts on human brains like a tiny zombie. As one Centers for Disease Control and Prevention expert warned several years ago: “This is a heat-loving amoeba. As water temperatures go up, it does better. In future decades, as temperatures rise, we’d expect to see more cases.”

But this is just a taste of things to come, as two parasite experts explain in a recent article, “Evolution in action: climate change, biodiversity dynamics and emerging infectious disease [EID].” That article is part of a special April issue of the Philosophical Transactions of the Royal Society B., whose theme is “Climate change and vector-borne diseases of humans.”

“The appearance of infectious diseases in new places and new hosts, such as West Nile virus and Ebola, is a predictable result of climate change,” as the news release explains. The article examines our “current EID crisis.”

Coauthor Daniel R. Brooks explains: “It’s not that there’s going to be one ‘Andromeda Strain’ that will wipe everybody out on the planet,” he said, referring to the deadly fictional pathogen. But he warns: “There are going to be a lot of localized outbreaks that put a lot of pressure on our medical and veterinary health systems. There won’t be enough money to keep up with all of it. It will be the death of a thousand cuts.”

Many tropical diseases are tropical because their insect or animal host prefer warmer climates. A 2015 report on neglected tropical diseases by the World Health Organization (WHO) pointed out that “climate variability and long-term climate changes in temperature, rainfall and relative humidity are expected to increase the distribution and incidence of at least a subset of these diseases.” For instance, WHO notes, “dengue has already re-emerged in countries in which it had been absent for the greater part of the last century.”

The Congressionally-mandated 2014 National Climate Assessmentconcurs: “Large-scale changes in the environment due to climate change and extreme weather events are increasing the risk of the emergence or reemergence of health threats that are currently uncommon in the United States, such as dengue fever.”

“Some of the neglected tropical diseases are no longer strictly tropical,” said Dr. Dirk Engels, the director WHO’s Department of Control of Neglected Tropical Diseases, in a statement.
Certainly there have been major advances in the fight against many tropical diseases, but those are primarily due to medical advances and investments in public health. Such investments remain a top priority in a warming world. But the kind of extreme climate change humanity faces on our current path of unrestricted carbon pollution makes the job harder for all those focused on public health around the world.

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The following is from the introduction to the academic study Romm mentions, “Climate change and vector-borne diseases of humans.”

This theme issue arose out of our perception that while it is widely recognized that an important impact of climate change on human health is likely to be via effects on vector-borne disease (VBD) transmission, the complexity of the biological and non-biological susceptibility modifying pathways by which such effects arise and combine to influence transmission is less well understood. This has made reliable appraisals of the potential effects of climate change and variability on VBDs complicated and represents a serious problem in developing more robust tools to assess the risk of climate change affecting VBDs in populations residing under different social and geographic contexts. This issue thus aims to provide not only an up-to-date synthesis of current knowledge of, and key research in, the impact of various individual components of climate change (biological, non-biological, evolutionary and economic factors), but also, crucially, to reveal and highlight the need (and potential means) to address the effects of multiple factor interactions, nonlinearities and human reflexivity if we are to develop and establish a more rigorous agenda for future research, including the provision of useful informatics for informed public health policy-making, in this important area of climate change studies.

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