DNA in Viking feces sheds new light on 55,000-year-old relationship between gut companions
Researchers at the University of Copenhagen have genetically sequenced the whipworm, one of the oldest human parasites, using stool samples from Viking latrines. The mapping depicts the parasite's global distribution and its complex interactions with people, which can both make us healthy and ill.
Researchers from the Department of Plant and Environmental Sciences at the University of Copenhagen and the Wellcome Sanger Institute (UK) have performed the largest and most thorough genetic analysis of the whipworm, one of the oldest parasites found in humans, using fossilized eggs in up to 2500-year-old feces from Viking settlements in Denmark and other nations.
The research, which was published in Nature Communications, offers brand-new information regarding the parasite's evolution and early dispersal. This information can be used to make efforts to stop the parasite's proliferation and development of drug resistance.
According to the study, over thousands of years, the parasite and human have evolved a delicate relationship in which the parasite tries to remain "under the radar" in order to avoid being repelled, giving it more time to infect new people. It is known from prior studies that the whipworm activates the human immune system and gut flora, which is advantageous to both the host and the parasite.
In developed nations, whipworm (Trichuris trichiura) is now uncommon and typically only causes minor issues in healthy people, but the parasite is thought to impact 500 million people in developing nations.
Our mapping of the whipworm and its genetic development makes it simpler to design more potent anti-worm drugs that can be used to prevent the spread of this parasite in the world's poorest regions, according to Professor Christian Kapel of UCPH's Department of Plant and Environmental Sciences. "Whipworm can lead to serious illness in people who are malnourished or have impaired immune systems.
Fossilized latrine excrement from Copenhagen and Viborg
Researchers were able to investigate the genetic makeup of thousands of years-old whipworms using eggs rather than worms. The inside DNA of the eggs has been well conserved when they have been buried in moist soil because of the exceptionally durable chitin in their capsules.
The researchers isolated the eggs under a microscope, sieved them from the stool, and subjected them to refined genetic analyses that the researchers have been perfecting for years in previous studies using fossilized stool samples that were previously discovered in the latrines of Viking settlements in Viborg and Copenhagen.
The eggs are designed to survive in soil for long periods of time, which is fortunate for us. Under ideal conditions, even the parasite's genetic material can be preserved extremely well, and some of the oldest eggs that we've extracted some DNA from are 5000 years old. It has been quite surprising to fully map the genome of 1000-year-old well-preserved whipworm eggs in this study.
Samples of archaeological stools from various sites were analyzed by the researchers. These modern genetic samples, which were taken from whipworm-infected individuals worldwide, are contrasted with the ancient genetic ones. By doing this, scientists have gained a general understanding of the worm's genome and its ten thousand-year history of evolution.
According to the so-called "out of Africa" idea on human migration, it is not surprising to see that the whipworm appears to have moved from Africa to the rest of the world alongside humans some 55,000 years ago, says Christian Kapel.
Can remain undetected for months in the intestine.
In the gut of a healthy person, a whipworm can develop to a length of five to seven centimeters and remain undetected for several months. It continues to lay eggs throughout this time, and the eggs are excreted through feces. Whipworm can result in a variety of gastrointestinal illnesses, malnutrition, and even a delay in a child's development in persons with compromised immune systems.
Worms are disseminated through the fecal-oral channel, which means that tiny parasite eggs in the soil can contaminate food or drink before entering the mouth of a new host.
Their entire life cycle is designed to survive in soil for as long as possible, according to Christian Kapel. "The eggs lie in the ground and develop for about three months. Once mature, eggs can survive in the wild for even longer, as they wait to be consumed by a new host in whose digestive tract they will then hatch.
As a result, in our region of the world, the prime years for these worms occurred when personal cleanliness, kitchen and bathroom conditions, and other factors were very different from what they are now.
Although the whipworm is extremely rare in the industrialized part of the world today, favourable conditions for its spread still exist in less developed parts of the world, according to Christian Kapel. "During the Viking Age and well into the Middle Ages, one didn't have very sanitary conditions or well-separated cooking and toilet facilities, which allowed the whipworm far better opportunities to spread," he adds.
University of Copenhagen - Faculty of Science
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