Around 2000 years ago, the Romans moved into Europe.
They built public latrines, or toilets, with many seats and washing areas. And they built sewerage systems, brought in drinking water from aqueducts, and heated public baths for washing.
They even had laws to keep the towns free of human waste and trash.
But new archeological research shows that baths and public toilets with washing areas did not get rid of intestinal parasites.
In fact, parasites like whipworm, roundworm, and Entamoeba histolytica dysentery slowly increased, compared to the Iron Age before the Romans ruled Europe.
Dr. Piers Mitchell conducted the research. He is from the Archaeology and Anthropology Department of Cambridge University in England.
His research suggests that "Roman toilets, sewers and sanitation laws had no clear benefit to public health," he said. "Roman baths surprisingly gave no clear health benefit, either."
Intestinal parasites and ectoparasites -- such as lice – were widespread, he said.
The study used samples from ancient Roman times to assess "the health consequences of conquering an empire."
Mitchell gathered evidence of parasites in ancient latrines, human burials and "coprolites" — or fossilized feces. He also examined combs and cloth from different Roman Period excavations, or historical sites, across the Roman Empire.
Although the Romans were known for regular bathing, Mitchell found lice and fleas were just as widespread as in earlier times. The Vikings and medieval people did not have the same culture of bathing as the Romans.
He found evidence of special combs for removing lice from hair. Getting rid of lice could have been something many people did every day in the Roman Empire.
Mitchell said "modern research shows that toilets, clean drinking water and removing feces from the streets all decrease risk of infectious disease and parasites."
So, why did parasites such as whipworm and roundworm increase even when cleaner methods were introduced by Romans?
He said it may have been the warm waters of the bathhouses that people shared. The waters were not changed often, and scum, or a layer of human dirt and cosmetics, would float on the top of the bathing water.
"Clearly, not all Roman baths were as clean as they might have been," Mitchell said.
Another possibility from the study: Romans used human waste to fertilize crops. Now, in modern times, we know the waste must not be used for many months before adding it to fields. Otherwise, it can spread parasite eggs that survive in plants.
"It is possible that sanitation laws requiring the removal of feces from the streets actually led to reinfection of the population as the waste was often used to fertilize crops planted in farms surrounding the towns," Mitchell said.
The study also found that fish tapeworm eggs were widespread in the Roman Period, compared to earlier times in Europe. Mitchell said this might be because the Romans loved a sauce called "garum."
It was used both for eating and as medicine. Garum was made from pieces of fish, herbs, salt and other flavors. It was not cooked, but left out in the sun to ferment. It was traded across the empire, so it may have transported the fish tapeworm along with the sauce, Mitchell said.
"The manufacture of fish sauce and its trade across the empire in sealed jars would have allowed the spread of the fish tapeworm ... to people all across the empire.
"This appears to be a good example of the negative health consequences of conquering an empire," he said.
There is an upside, Mitchell added: "It seems likely that while Roman sanitation may not have made people any healthier, they would probably have smelt (smelled) better."
The findings are published in the journal Parasitology.
I'm Anne Ball.