Ancient Fossils Reveal Climate Change Causes Rise in Parasites

We may be in for some troubled times as the climate changes. Scientists have looked to the past, and have found that during climate change events, parasitic infections rose; this could mean that these same parasites may also be on the rise in the future.

In this latest study, the researchers looked at clams from the Holocene Epoch, which began 11,700 years ago. They found that during this time period, there was an upsurge in parasitic trematodes, or flatworms, that infected the clams. Trematodes are internal parasites that affect mollusks and other invertebrates that inhabit estuaries, coastal bodies of brackish water that connect rivers and the open sea.

"Because they have soft bodies, trematodes do not leave body fossils," said John Huntley, one of the researchers, 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. When compared to documented rises in sea level more than 9,300 years ago, we found that we currently are creating conditions for an increase in trematodes in present-day estuarine environments. This could have harmful implications for both animals and human health, including many of the world's fisheries."

In fact, it seems that the changing climate could cause an increase in the number of trematodes. These modern-day trematodes will first infect mollusks, which are eaten by shore birds and mammals. This, in turn, could infect those higher up the food chain.

"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," said Huntley.

The findings are published in the journal Proceedings of the National Academy of Sciences.

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