The Earth is facing a number of challenges due to climate change. A new fossil study suggests that climate change is also leading to more parasitic infections.

John Huntley, an assistant professor of geological sciences at the University of Missouri, suggests that trematodes are internal parasites or flatworms, which affect molluscs as well as other invertebrates inhabiting estuaries. An estuary is a water body that is formed where freshwater from the rivers and streams flow into the ocean and mixes with seawater.

Huntley explains that he examined pre-historic clam shells, which he gathered from the Pearl River Delta in China, to find hints on how the clams got affected by global warming that resulted in an increase of parasites on the planet.

Huntley's study involved fossil study of the clams, which belonged to the Holocene Epoch (that began 11,700 years ago). The study suggests that modern day rise of the sea level mimics similar conditions, which led to increase in parasitic trematodes. The research warns that human infections from similar parasites may occur. Huntley suggests that health agencies and communities should prepare from such a parasitic infection outbreak.

The study reveals that bodies of trematodes are soft and they do not leave fossils. However, the clam shells that got infected with the parasite developed pits and the clam grew around the parasite so that they can keep the parasite out. The prevalence of the pits gives clues on the adaptation pattern of the clams to fight with 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 animal and human health, including many of the world's fisheries," says Huntley.

The research suggests that symptoms of parasitic infection in humans can be found in many organs such as gall bladder, liver and more. Parasitic infections can cause fever, chest pain and brain inflammation, which can also be fatal. About 56 million humans worldwide suffer from at least one foodborne trematode infections.

Huntley compared the fossil data found in China along with previous data collected from Adriatic Sea. The comparison reveals that an increasing occurrence of clam shell pits indicates a greater incidence of the parasites during times of sea level rise in both the fossils collected from Adriatic Sea and from China.

The study has been published in the journal Proceedings of the National Academy of Sciences (PNAS).