Parasitic worms (aka helminths) are not the most pleasant thing to think of – these organisms have plagued humans throughout history, slithering inside our bodies, exploiting their hosts and draining resources. In current-day Europe and North America, infection with these creatures is thankfully rare and is typically found in travelers going into endemic areas, typically tropical and subtropical regions. Helminth infections are classed as one of the top neglected tropical diseases by the World Health Organization (WHO).
This rarity has not always been the case, and many archaeological studies have found the eggs of these helminths in Europe and North America. These eggs are typically environmentally resilient and can remain morphologically identifiable for hundreds of years.
Interestingly enough, the detection of eggs can provide insight into the social situation of the unfortunate infected person. For example, infection of worms transmitted by the fecal-oral route (such as the roundworm, Ascaris, and the whipworm, Trichuris), may suggest poor sanitation and hygiene practices. On the other hand, some tapeworms are transmitted by undercooked food like red meat (Taenia spp.) and freshwater fish (Diphyllobothrium latum, syn. Dibothriocephalus latus).
As you can imagine, the best place to find the fecal-associated worms are in ancient toilets, communal deposits, and the abdominal regions of mummified or skeletal remains. The latter sample type is the most challenging to acquire but is often the most informative, as they can be combined with individual characteristics like age and sex.
Researchers analyzed the prevalence rates of helminth infections from the Prehistoric to the Industrial era, and how this rate changed over time, describing their findings in the PLOS Neglected Tropical Diseases.
Scientists examined soil samples from the abdominal region of 464 individual skeletal remains buried at 17 sites around the UK, finding that over a quarter of the samples had helminth infestations.
But which time period was the most inundated with these parasitic fiends?
While they detected infections across all periods, the highest was in… drum roll... Roman and Late-Medieval periods.
The Romans may be a surprising result to some (the late-medieval period not so much), as the ancient Romans were known for the introduction of large multi-seat public latrines, clean water, sewers, and aqueducts. Modern research has shown that access to clean drinking water and toilets help to decrease gastrointestinal infections of parasites.
However, this work and previous studies indicate that the Roman sanitation technology may not have been the parasitic preventative we once thought. This may have been because human waste from the public latrines was used to fertilize crops in fields, and contaminated food products could have reinfected populations.
The study also highlighted another interesting time period: the industrial age. The scientists discovered that two of the three sites contained very few (or no) parasites, but the London site contained very high levels of infection – as may be expected in a cramped urban area with poor sanitation. The low rate in the other two sites, Oxford and Birmingham, may be because of clean well-based water access.
Luckily for current UK citizens, most fecal-contracted worms are no longer endemic, and this may be due to improved sanitation in the 19th and early 20th centuries and the development of modern anthelminthic drugs.
Whilst these results should be taken with a grain of salt – as the prevalence rates may have been an underestimated due to the taphonomic (how organisms decay and become fossilized) method or sample processing – this research is important and by looking into the past, scientists can come up with ways of managing parasites without heavy drug intervention.