Scientists find earliest known evidence of parasitic worm that now infects millions

Scientists find earliest known evidence of parasitic worm that now infects millions
By Ryan Whitwam Jun. 22, 2014 10:31 am schistosomiasis

Archaeologists excavating ancient human settlements in northern Syria have come across an unusual specimen. The egg of a parasitic worm that causes the disease schistosomiasis was found in the remains of a child who died more than 6200 years ago. The parasite, known as Schistosoma or “blood flukes,” now infect more than 200 million people worldwide. This is the earliest known evidence of this type of parasitic infection, and perhaps the beginning of the current epidemic.

The skeleton dates back to a time and place where humans had first started using irrigation to enable large-scale farming. This expanded food supply dramatically, but irrigation also changes the local landscape, which sometimes has unintended consequences. In the case of schistosomiasis, the Schistosoma flatworm gains entry to humans through contact with infected shallow water — exactly the sort of thing you’d find in irrigated fields.

Schistosoma begins its life cycle when the eggs are ingested by snails in fresh water. The microscopic adult worms are eventually released and go on the hunt for a larger host. Several species of Schistosoma are known to target humans, which are infected when the worms burrow into the skin. They colonize the bladder, kidneys, and intestines as the host continues shedding eggs that keep the cycle going.

The Schistosoma egg discovered in these remains was near the pelvis of the host, which is right where you’d expect to find them in an infected individual. Schistosomiasis can result in bleeding, abdominal pain, fever, and even paralysis of the legs if left untreated. The infection can be self-limiting, but can easily persist for years. It’s no known if the child died as a result of schistosomiasis, but it’s certainly possible it was a contributing factor. Medications exist to treat the disease now, but that hasn’t stopped it from becoming incredibly common throughout the developing world.

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