Antique parasite worms its way into human history

June 19, 2014 by Richard Ingham,
Iraqis wade in the waters of the Euphrates River in Hindiya on May 19, 2009

Forensic sleuths said Thursday they had found the oldest known egg of the bilharzia parasite, revealing how human advancement enabled a tiny freshwater worm to become a curse for millions.

In a letter published by the journal The Lancet Infectious Diseases, a team of archaeologists and biologists said they found a 6,200-year-old egg of the feared intestinal parasite in an ancient grave in northern Syria.

The site, Tell Zeidan, is in the valley of the Euphrates—part of the fabled "Fertile Crescent" where humans settled down to farm nearly 8,000 years ago, making the historic leap from hunter-gatherer.

The team excavated the skeletal remains of 26 people from the burial site and gently sifted through sediment collected from the pelvic area of each.

The painstaking work turned up an egg just 132 millionths of a metre long that under a powerful microscope turned out to be pale brown, stained by millennia-long exposure to the soil.

The egg, say the researchers, is from one of two species of schistosomes—flatworms that cause bilharzia, which affects hundreds of millions of people in tropical Asia, Africa and Latin America.

Schistosomes burrow into the skin when someone wades into freshwater, and develop into adult worms before invading the kidney and bladder or intestines.

Luxuriating in the balmy flow of blood, they mate, and their eggs are excreted in urine or faeces, thus exposing more people to the disease, which is also called schistosomiasis or snail fever.

Infection—typically signalled by blood in the urine—can result in kidney failure, bladder cancer, malnutrition and anaemia.

Children play the Bandama river in the Ivorian region of Kossou on March 10, 2009, at severe risk of Bilharziasis

Riddle of the parasite

Recent DNA analysis of schistosomes suggested the flatworm evolved in Asia and spread from there to Africa and beyond.

But how this happened was unclear until now.

Migration through early human settlement in the Middle East, via the irrigation system of the Fertile Crescent, is a likely answer, according to the letter.

The people at Tell Zeidan grew wheat and barley in highly arid conditions, which suggests they developed an irrigation system to water their crops, it says.

If so, wading in the water channels would have been the likely infection source for the individual who carried the parasite, according to the probe headed by Piers Mitchell at Britain's University of Cambridge.

"Our findings suggest that crop irrigation 6,000 years ago in the Middle East enabled schistosomiasis to spread to people living there, and so triggered the enormous disease burden that schistosomiasis has caused over the past 6,000 years," the letter says.

According to the UN's World Health Organisation (WHO), more than 42 million were treated for bilharzia in 2012, and 249 million were given preventive treatment with praziquantel, the frontline drug for controlling the parasite.

The latest discovery also fits with other pieces of evidence.

They include the remains found at many ancient Middle East sites of freshwater Bulinus snails that provide a host for the parasite at an early stage of its life cycle.

There is also an ancient medical text found in modern-day north Iraq whose author described diseases that caused blood-stained urine.

And in 2002, schistosomes were found in Egyptian mummies—evidence that the wretched parasite was a problem for the people of the Nile 5,200 years ago.

Infection through irrigation could be the earliest known example of human technology enabling a disease to spread.

The health consequences probably had "a significant impact upon early civilisations in the region," said Mitchell.

Explore further: Scientist uncovers links connecting environmental changes with spike in infectious disease

More information: Paper: www.thelancet.com/journals/lan … (14)70794-7/fulltext

Related Stories

Scientist uncovers links connecting environmental changes with spike in infectious disease

May 21, 2014
National Museum of Natural History scientist Bert Van Bocxlaer and an international team of researchers revealed that anthropogenic changes in Africa's Lake Malaŵi are a driving force behind the increase of urogenital schistosomiasis, ...

Mummies tell history of a 'modern' plague

May 23, 2011
Mummies from along the Nile are revealing how age-old irrigation techniques may have boosted the plague of schistosomiasis, a water-borne parasitic disease that infects an estimated 200 million people today.

Brazil claims successful test of parasite vaccine

June 13, 2012
Brazilian researchers say they have successfully tested a vaccine against schistosomiasis, a disease caused by parasitic worms that afflicts more than 200 million people worldwide.

Progress in understanding immune response in severe schistosomiasis

April 16, 2014
Researchers at the Sackler School of Graduate Biomedical Sciences at Tufts and Tufts University School of Medicine (TUSM) have uncovered a mechanism that may help explain the severe forms of schistosomiasis, or snail fever, ...

More research called for into HIV and schistosomiasis coinfection in African children

April 17, 2014
Researchers from LSTM have called for more research to be carried out into HIV and schistosomiasis coinfection in children in sub-Saharan Africa. In a paper in The Lancet Infectious Diseases LSTM's Professor Russell Stothard, ...

Recommended for you

Study ends debate over role of steroids in treating septic shock

January 19, 2018
The results from the largest ever study of septic shock could improve treatment for critically ill patients and save health systems worldwide hundreds of millions of dollars each year.

New approach could help curtail hospitalizations due to influenza infection

January 18, 2018
More than 700,000 Americans were hospitalized due to illnesses associated with the seasonal flu during the 2014-15 flu season, according to federal estimates. A radical new approach to vaccine development at UCLA may help ...

Flu may be spread just by breathing, new study shows; coughing and sneezing not required

January 18, 2018
It is easier to spread the influenza virus (flu) than previously thought, according to a new University of Maryland-led study released today. People commonly believe that they can catch the flu by exposure to droplets from ...

Zika virus damages placenta, which may explain malformed babies

January 18, 2018
Though the Zika virus is widely known for a recent outbreak that caused children to be born with microencephaly, or having a small head, and other malformations, scientists have struggled to explain how the virus affects ...

Certain flu virus mutations may compensate for fitness costs of other mutations

January 18, 2018
Seasonal flu viruses continually undergo mutations that help them evade the human immune system, but some of these mutations can reduce a virus's potency. According to new research published in PLOS Pathogens, certain mutations ...

Study reveals how MRSA infection compromises lymphatic function

January 17, 2018
Infections of the skin or other soft tissues with the hard-to-treat MRSA (methicillin-resistant Staphylococcus aureus) bacteria appear to permanently compromise the lymphatic system, which is crucial to immune system function. ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.