The ancient Romans left evidence of their expansive empire across the Eurasian and African continents, and to the benefit of modern science, that evidence includes a good deal of human feces.

The parasites that like to call intestines and feces home, have helped an archeologist determine that Romans — long presumed the benefactors of building more sanitary, and by extension healthier, cities — were not necessarily any healthier than those who lived in the societies that preceded and followed them.

In research published this week in the journal Parasitology, University of Cambridge archeologist Piers Mitchell found that the presence of certain easily transferable intestinal parasites such as roundworm and Entamoeba histolytica, a microbe that causes dysentery in humans, was not lower during the reign of the Roman Empire when compared with the Iron and Bronze Age before it, and the medieval period that came after it.

LISTEN | Romans plagued by parasites

Mitchell based his comparative study on evidence gathered from ancient Roman latrines, human burial sites and samples of fossilized feces called "coprolites." He examined the prevalence of intestinal parasitic eggs, which remain at measurable levels in samples thousands of years after other fecal material has decomposed.

He also looked at the presence of ectoparasites, or parasites that live on the outside of the body, such as lice and fleas, on things like textiles and combs.

A latrine from ancient Roman Caracalla baths displayed in Venice. (Vincenzo Pinto/Getty) For both classifications of parasite, the Romans were no better off.

In an interview with CBC Radio's Quirks & Quarks set to air Saturday at noon ET and available online here, Mitchell said the results of the study were counterintuitive, to say the least.

"I didn't see any drop whatsoever compared to the Bronze Age or the Iron Age, which was not what I expected at all," he told host Bob McDonald.

"I had to go back and check the data to make sure I wasn't making a mistake."

The Romans are credited with introducing sanitation to Europe about 2,000 years ago. They built elaborate public latrines with, in some cases, dozens of seats and hand-washing facilities, as well as extensive sewer systems to channel human waste away from city centres and aqueducts to provide a dependable flow of clean water. Some Romans also had access to lavish bathhouses, and bathing was a central part of the culture for generations.

Conversely, complex sewer systems and regular bathing were essentially unheard of in Viking and medieval cultures.

The Romans' dedication to sanitation should have translated into a drop in parasite rates. Or so archeologists had thought.

"If you look at the modern evidence that's collected in the developing world today, if you're in a household with a toilet the chance of getting diarrhea and intestinal parasites is much less than if you don't have a toilet," Mitchell said, adding that once he had collected his results it became clear that "the whole package of sanitation sadly did not improve the health of the population under the Roman Empire."

Parasites 'all over your salad'

The obvious question that faced Mitchell was why?

The Romans, it turned out, had a rather unsavoury habit of using fresh human feces to fertilize crops, rather than letting the feces decompose for about a year — ample time for parasites and their eggs to perish.

"If you use the feces fresh, then you just re-infect the population by having viable parasite eggs all over your salad vegetables," Mitchell said.

What's more, the Roman penchant for bathing didn't reduce levels of ectoparasites. Comprehensive analysis of evidence from around the European continent showed that Romans were just as lice and tick riddled as those in the Viking or medieval periods.

What's more, the lukewarm bath water may have helped encourage the persistence of intestinal parasites that may have eked out onto the outer limits of human orifices.

At the very least, however, the Romans may have been slightly "less smelly" and resided in more livable cities than their Bronze and Iron Age and medieval counterparts.