(CN) — Since the dawn of human history, parasitic worms have plagued us. Evidence of this intestinal scourge has been found in the mummified feces of humans dating back thousands of years, and detailed accounts appear in the ancient writings of Hippocrates and the Bible.
Even today, parasitic worms known as helminths are among the World Health Organization’s top neglected diseases, infecting an estimated 1.5 billion people around the world. The worms are transmitted through eggs in human feces that contaminate soil and water, causing a range of symptoms, from stomach discomfort to anemia, chronic malnutrition and physical impairment, especially in children.
A study published Thursday in PLOS Neglected Tropical Diseases establishes how prevalent parasitic worms were in medieval Europe and which factors mirror conditions in the modern world.
By all accounts, the Middle Ages was a time of immense suffering, replete with famine, war, and plague, including the Black Death, which killed about a third of Europeans between 1347 and 1350.
It has long been known that parasitic worms riddled the human population. But the study, written by the University of Oxford’s Adrian Smith and his colleagues, yielded valuable data on how pervasive helminths were in the general population. Analyzing samples gathered from 589 graves at seven sites dated between 680 and 1700 A.D., Smith and other researchers discovered two common parasites, roundworm and whipworm, at each site, and two food-derived parasites — both tapeworms — at four of the sites.
“The widespread presence of helminth eggs in archaeological deposits indicates that helminths represented a considerable burden in past European populations,” the study authors wrote.
Effective antiparasite drugs were developed in the early 1960s, making fecal-oral parasites almost nonexistent in Europe, limited primarily to the occasional traveler. However, parasites remain endemic in populations in some developing countries, depending on socioeconomic factors, cultural practices and the degree of urbanization.
To contextualize their data, researchers compared their findings historical findings from sites in the United Kingdom, Germany and the Czech Republic with those from modern regions suffering from parasite endemics. What they found astounded them. Hundreds of years later, certain populations continue to suffer from parasites at levels extinct for decades in developed countries.
“The rates of (roundworm and whipworm) infection in the medieval populations… were comparable to those reported within modern endemically infected populations,” the authors wrote.
Researchers found that infection rates in medieval populations were similar between men and women, while rates were higher in children. These findings align with modern populations, in which children tend to have higher infection rates than adults.
The findings help scientists understand how to reduce parasitic infections currently rampant in certain populations, because infections in Europe were reduced long before modern drugs were developed. The reduced rate of infection was likely associated with changes in water, hygiene, agricultural practices and sanitation.
“The European… experience supports the idea that these WASH measures (water, sanitation and hygiene) can be successful in the absence of modern anthelminthic drugs even with high rates of infection in the pre-intervention communities,” the study concluded.
So how did researchers come to learn so much about individuals who died centuries ago? Using comprehensive anthropological analysis, researchers collected pelvic soil samples from each grave and rehydrated them overnight before sifting the soil through a sieve. Then they examined the parasitic worm eggs they found under a microscope.
The study represents the first of its kind to examine results from such an extensive set of sites, both individually and geographically.
Smith and his colleagues hope their study serves as a baseline for future archaeological studies and a resource for scientists battling parasitic infections in modern populations.
“Even in the modern era it remains unclear whether chemotherapy alone is sufficient to control (parasitic infections) and it is therefore appropriate to explore other measures including WASH more thoroughly,” they wrote.