According to a new study, ancient Egypt suffered from Nile-born parasites at high rates.

Sole researcher Piers Mitchell, a biological anthropologist from the University of Cambridge, studied the CT scans of 31 Egyptian and Nubian mummies for diseased tissues and evidence of parasitic infections, according to Scientific American. He also conducted DNA analysis in available soft tissues.

In his published study, he found that 65% of the mummies had schistosomiasis, 40% had head lice, 22% had falciparum malaria and 10% had visceral leishmaniasis.

How the Nile River created a parasite hot spot

Popular Mechanics explains that the Nile River turned a normally arid environment into a location that water-based parasites can thrive. The river allowed mosquitos to breed and spread illnesses such as malaria and filariasis, while irrigation systems using the water from the Nile exposed farmers to schistosomiasis, according to the study.

In the study, Mitchell explains that “despite the low rainfall in most of the region, the River Nile acted as a conduit for tropical water-born parasites that would not normally be found in arid regions. Insect vectors ranged from mosquitos breeding in the oases and marshlands such as Fayum submerged by the annual Nile floods, to sandflies endemic to the savannah acacia forests of Nubia.”

Biological anthropologist Ivy Hui-Yuan Yeh from Nanyang Technological University told Scientific American that anyone who uses infected water is at risk of getting an infection.

The effects of these parasitic infections

Sixty-five percent of the mummies Mitchell studied had a parasitic infection known as schistosomiasis, a parasitic worm that comes from fresh water snails, per the World Health Organization (WHO). These parasitic worms live in the blood vessels and the eggs created are released through human feces and urine.

Transmissions occur when these infected feces and urine enter freshwater, where the eggs hatch and infect new hosts. Common symptoms of schistosomiasis includes bloody urine and stools, organ damage and reduced capability to work, per WHO.

The study also found that 40% of the mummies had head lice, while 22% of mummies had the most dangerous form of malaria, per Scientific American. Mitchell also found that 10% of mummies had a parasitic disease called leishmaniasis, which is known to enlarge internal organs.

He shares in the study that “such a disease burden must have had major consequences upon the physical stamina and productivity of a large proportion of the workforce.”

Considering the high amounts of the population sick, Mitchell shared, “... The Egyptians managed to complete major building projects such as their pyramids, temples, and ornate tombs for kings and nobility. The widespread anemia from parasite infection in ancient Egypt meant they would have struggled to build these monuments using their own diseased workforce alone. They could only build the ancient Egypt we see today using imported labor, such as slaves captured during military campaigns,” per Popular Mechanics.