Parasitic Infections Increase with Climate Change

Among the plethora of side effects caused by climate change, it is also threatening to increase parasitic infections, according to an analysis of ancient mollusk fossils.

Scientists often look to the past to discover secrets about the future, and they have done just that in a new study of clams from the Holocene Epoch, which began 11,700 years ago. According to the findings, published in the journal Proceedings of the National Academy of Sciences, current sea level rise may mimic the same conditions that led to an outbreak in human infections from parasitic worms, called trematodes or flatworms.

Trematodes are internal parasites that affect mollusks and other invertebrates living in estuarine environments. In this study, researchers from the University of Missouri-Columbia looked at prehistoric clam shells collected from the Pearl River Delta in China to see how they were influenced by both these parasites and climate change long ago.

"Because they have soft bodies, trematodes do not leave body fossils," lead study author John Huntley said in a news release. "However, infected clam shells develop oval-shaped pits where the clam grew around the parasite in order to keep it out; the prevalence of these pits and their makeup provide clues to how the clams adapted to fight trematodes."

The clams also showed evidence of sea level rise over 9,300 years ago, a time when conditions were akin to what they are now, suggesting that parasitic infections could rise again and threaten animals and human health, as well as various fisheries worldwide that depend on mollusks like clams and snails.

"While predicting the future is a difficult game, we think we can use the correspondence between the parasitic prevalence and past climate change to give us a good road map for the changes we need to make," Huntley added.

At least 56 million people globally suffer from one or more foodborne trematode infections, according to the World Health Organization. Symptoms of such parasitic infections include liver and gall bladder inflammation, chest pain, fever, and brain inflammation, and can be fatal.

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