The ancient Romans introduced sanitation systems that have been credited with bringing Europe out of pestilence. But did they?

In pre-Roman towns in Europe, sewage streamed through the streets and residents rarely bathed.

When the Romans came along, they provided clean drinking water and public latrines with hand washing stations. The Romans also required human waste to be removed from populated areas.

It is so entrenched in cultural lore that Roman conquest dramatically improved the quality of life in European towns that even the anti-Roman activists portrayed in Monty Python’s “Life of Brian” must admit it. When an insurgent wonders aloud what the Romans have ever done for the locals, a comrade feebly answers, “the aqueduct.” Another soon pipes up: “and the sanitation.” A third says, “Yes, the sanitation! You remember what the city used to be like.”

But, according to a new paper, these celebrated Roman advances did nothing to slow the spread of common intestinal parasites.

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Piers Mitchell, Ph.D., an archeologist at Cambridge University, surveyed archeological evidence from pre-Roman towns in Europe and the Middle East and compared it to studies of Roman toilets, looking for evidence of parasites that cause gastrointestinal disease.

“Modern clinical medicine would suggest that [Roman infrastructure] would improve the health of the population,” Mitchell told Healthline.

But, at least in gastrointestinal terms, it did not.

Take the parasites roundworm and hookworm. Spread through the ingestion of feces, they are exactly the sorts of parasites one would expect to dwindle when a population gets running water, such as that primitively provided by the aqueducts.

But they became slightly more common under Roman rule, according to Mitchell’s paper, published today in the journal Parasitology.

Before the Roman conquest, fish tapeworm, which is acquired by eating uncooked fish, had been found only in northern Europe. The Romans, who had a penchant for a fermented fish sauce called garum, likely spread it across the empire, according to the paper.

Archaeological evidence also shows that anemia was fairly widespread in the Roman Empire. Gastrointestinal parasites are one cause of anemia.

Roman rule “did some things very well, but it brought with it unanticipated negative consequences, too,” said Richard Billows, Ph.D., a professor of ancient history at Columbia University. “Having proper sewage and drainage facilities and having an adequate supply of clean drinking water obviously has benefits, including health benefits. What Mitchell is saying is that in addition to those benefits, you got some other things that were less appealing, namely the spread of these intestinal parasites.”

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Mitchell doesn’t blame the aqueducts or the public toilets where people sat cheek-to-jowl to do their business. Rather, the paper suggests that the Roman sanitation system had both gaps and unintended consequences.

Not everyone in a Roman city, even Rome, was connected to the primitive sewage system that served the public toilets, according to Glenn Storey, Ph.D., an associate professor of classics anthropology at the University of Iowa. The feces that ended up in cesspits, chamber pots, and in the streets were removed — as required by Roman law.

In some cases, human feces were used to fertilize crops. Roundworm and hookworm could be passed in this way to a person who later ate those crops, which likely accounts for their increased prevalence.

The celebrated Roman baths may also have contributed to the spread of parasites, Mitchell suggests.

“We don’t know how often the water in the baths was changed, but I suspect for the hot baths it wasn’t very often because it cost so much fuel to heat, and of course Galen and other Roman physicians told people who were sick to go soak in the baths,” Storey said.

Roman science did not yet include bacteria or parasites.

As for the fish tapeworm, Mitchell thinks the likeliest vector was a fish sauce beloved by the Romans and traded throughout the empire. The sauce was pickled, not cooked, meaning that tapeworm larva could survive.

“With the possibility of easy and widespread travel and exchange of goods came the spread of certain kinds of chronic illness and the occasional outbreak of empire-wide plagues,” Billows said. “It’s not so much that these parasites existed — that’s no surprise really — but that they were able to travel and spread throughout the Mediterranean region as a result of the empire.”

Rome itself experienced major disease outbreaks about every decade, Storey said, probably for the same reason.

“It may not be the sanitation problem so much as the disease loads that come from other places,” he said. “The passing of disease is even worse than the parasite loads that people probably adapted to, to a certain extent.”

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Mitchell’s paper shows that parasites linked to poor hygiene didn’t simply go away when the Romans showed up.

“If you have public baths to wash, that’s going to make people smell better. If you have public latrines in the middle of town, it’s more convenient,” Mitchell said. “So there’re benefits. But what’s surprising is that we don’t see any health benefits.”

It’s difficult to measure with much nuance how well people were more than 2,000 years ago.

But Roman subjects couldn’t have been too sick because population numbers grew.

“What intestinal parasites tend to do is not prematurely kill people, as far as I know, but cause a certain amount of chronic difficulties that are survivable,” Billows said.

The spread of illnesses can be viewed as the “downside” of the more modern, industrialized lifestyle the Romans introduced.

“The question is, is it worth the upside? And on the whole it clearly was, because Europe was more heavily populated at the height of the Roman Empire than at any other time before the 18th century,” said Billows.