Human infection from parasites in the Bronze Age


New research published this month (August 2019) in the journal Parasitology shows how the prehistoric inhabitants of a settlement in eastern England were infected by intestinal worms caught from foraging for food in the lakes and waterways around their homes.

The Bronze Age settlement at Must Farm consisted of wooden houses built on stilts above freshwater marshes. Wooden causeways connected islands and dugout canoes were used to travel along water channels. The village burned down in a catastrophic fire around 3,000 years ago and collapsed into the water. Artefacts from the houses, including food, cloth and jewellery, were preserved in the mud below the waterline.

However, also preserved in the surrounding mud were waterlogged “coprolites” – pieces of human faeces – that have now been collected and analysed by archaeologists at the University of Cambridge. They used microscopy techniques to detect ancient parasite eggs within the faeces and the surrounding sediment.

Very little is known about the intestinal diseases of Bronze Age Britain. The one previous study, of a farming village in Somerset, found evidence of roundworm and whipworm: parasites spread through contamination of food by human faeces. The ancient excrement of the Anglian marshes tells a different story. “We have found the earliest evidence for fish tapeworm, Echinostoma  worm and giant kidney worm in Britain,” said study lead author Dr Piers Mitchell of Cambridge’s Department of Archaeology. “These parasites are spread by eating raw aquatic animals such as fish, amphibians and molluscs. Living over slow-moving water may have protected the inhabitants from some parasites but put them at risk of others if they ate fish or frogs.”

The water in the fens would have been quite stagnant, due in part to thick reed beds, leaving waste accumulating in the surrounding channels. Researchers think it likely that this provided fertile ground for other parasites to infect local wildlife, which – if eaten raw or poorly cooked – then spread to village residents. “The dumping of excrement into the freshwater channel in which the settlement was built, and consumption of aquatic organisms from the surrounding area, created an ideal nexus for infection with various species of intestinal parasite,” said study first author Marissa Ledger, also from Cambridge’s Department of Archaeology.

Fish tapeworms can reach 10 metres in length and live coiled up in the intestines. Heavy infection can lead to anaemia. Giant kidney worms can reach up to a metre in length and gradually destroy the organ as they become larger, leading to kidney failure. Echinostoma worms are much smaller, up to 1cm in length, but heavy infection can lead to inflammation of the intestinal lining.

Working with colleagues at the University of Bristol’s Organic Chemistry Unit, the Cambridge team investigated whether coprolites excavated from around the houses were human or animal. While some were human, others were from dogs. “Both humans and dogs were infected by similar parasitic worms, which suggests the humans were sharing their food or leftovers with their dogs,” said Ledger.

The researchers compared their latest data with previous studies on ancient parasites from both the Bronze Age and Neolithic. Must Farm tallies with the trend of fewer parasite species found at Bronze Age compared with Neolithic sites. “Our study fits with the broader pattern of a shrinking of the parasite ecosystem through time,” said Mitchell. “Changes in diet, sanitation and human-animal relationships over millennia have affected rates of parasitic infection.”

However, Mitchell also points out that there has been a recent insurgence in infections from the fish tapeworm found at Must Farm. This is due to the popularity in the 21st century of fish-based foods such as sushi, smoked salmon and ceviche.

Source                 Heritage Daily

Text                      Alun Harvey


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