Using stool samples from Viking latrines, researchers at the University of Copenhagen have genetically mapped one of the oldest human parasites – the whipworm. The mapping reflects the parasite’s global spread and its interaction with humans, a delicate relationship that can make us healthier and sicker.
Using fossilized eggs in feces dating back 2,500 years from Viking settlements in Denmark and other countries, researchers from the Department of Plant and Environmental Sciences at the University of Copenhagen and the Wellcome Sanger Institute (UK ) performed the largest and most thorough genetic analysis of one of the oldest parasites found in humans – the whipworm.
The study, published in Nature Communication, presents completely new knowledge on the development and prehistoric dispersion of the parasite. This knowledge can be applied in efforts to prevent parasite drug resistance and its future spread.
The study suggests that humans and the parasite have developed a delicate interaction over thousands of years, whereby the parasite tries to stay ‘under the radar’ so as not to be pushed back, giving it more time to infect. new people. From other studies, whipworm is known to stimulate the human immune system and gut microbiome, to the mutual benefit of host and parasite.
While whipworm (Trichuris trichiura) is now rare in industrialized countries, and most often causes only minor problems in healthy individuals, the parasite is estimated to affect 500 million people in developing countries.
In people who are malnourished or have a weakened immune system, whipworm can lead to serious illness. Our mapping of whipworm and its genetic development facilitates the design of more effective anti-worm drugs that can be used to prevent the spread of this parasite in poorer regions of the world. »
Professor Christian Kapel, Department of Plant and Environmental Sciences, UCPH
Fossilized latrine poo from Copenhagen and Viborg
The eggs, not the worms, allowed the researchers to examine the genetic material of whipworms thousands of years old. Due to the extremely durable chitin in the egg capsules, their internal DNA was well preserved while the eggs were buried in moist soil.
Examining samples of fossilized feces that had previously been discovered in the latrines of the Viking colonies of Viborg and Copenhagen, the researchers isolated the eggs under a microscope, sieved them from the feces and subjected them to elaborate genetic analyzes that the researchers have been perfecting for years in previous studies.
“We have known for a long time that we can detect 9,000-year-old parasite eggs under the microscope. Fortunately for us, eggs are designed to survive in the soil for long periods of time. Under optimal conditions, even the genetic material of the parasite can be extremely well preserved. And some of the oldest eggs from which we have extracted DNA are 5000 years old. It was quite surprising to fully map the genome of well-preserved 1000-year-old whipworm eggs in this new study “, explains Christian Kapel.
The researchers examined archaeological stool samples from several locations. These ancient genetic samples are compared with contemporary samples obtained from people with whipworm around the world. This provided researchers with insight into the worm’s genome and how it evolved over tens of thousands of years.
“Unsurprisingly, we can see that whipworm appears to have spread from Africa to the rest of the world with humans around 55,000 years ago, following the so-called ‘out of Africa’ hypothesis of human migration. “, explains Christian Kapel.
Can live undetected in the gut for months
A whipworm can reach five to seven centimeters in length and live unnoticed in the intestine of a healthy individual for several months. During this time, he continuously lays eggs, which are expelled through feces. In people with weakened immune systems, whipworm can cause a wide range of gastrointestinal illnesses, malnutrition, and even stunted child development.
Worms are transmitted by the fecal-oral route, which means that microscopic parasite eggs in soil can spread to drinking water or food, after which they are ingested through the mouth of a new host.
“The eggs rest in the ground and develop for about three months. Once matured, the eggs can survive even longer in the wild, waiting to be consumed by a new host in whose digestive tract they will then hatch. Everything their life cycle is adapted to survive in the ground for as long as possible,” explains Christian Kapel.
So, the heyday of these worms in our part of the world was when our toilet and kitchen conditions, as well as our personal hygiene, were very different from those of today.
“In Viking times and up until the Middle Ages, we didn’t have very sanitary conditions or well-separated kitchen and toilet facilities. This allowed the whipworm to spread much better. Today, it is very rare in the industrialized part of Unfortunately, favorable conditions for the spread still exist in the less developed regions of the world, ”says Christian Kapel.
- The new study provides the first in-depth and comprehensive genetic mapping of whipworm. Until now, only limited segments of the genome were known.
- The parasite spread from Africa to the rest of the world with our human ancestors.
- Among other things, the researchers collected stool samples with whipworm eggs from Viking settlements in Denmark, Latvia and the Netherlands.
- The ancient genetic samples were compared with contemporary samples from people with whipworm from many countries in Africa, Central America, Asia and Europe.
- The United States Center for Disease Control (CDC) estimates that 604 to 795 million people are infected with trichuriasis worldwide. Source: Pullan, RL, Smith, JL, Jasrasaria, R. & Brooker, SJ (2014) Global number of infections and disease burden of soil-transmitted helminths in 2010. Parasite. Vectors 7, 37.
- The study is led by the University of Copenhagen’s Department of Plant and Environmental Sciences, Section of Organismal Biology and carried out in collaboration with the Wellcome Sanger Institute (UK).
University of Copenhagen – Faculty of Science
Doyle, SR, et al. (2022) Population genomics of ancient and modern Trichuris trichiura. Communication Nature. doi.org/10.1038/s41467-022-31487-x.