As far back as the 1920s, evidence of schistosomiasis was detected in mummies from the Nile River region, but only in recent years did the analysis of the antigens and antibodies of some of the individuals become possible.
This latest study tested desiccated tissue samples from two Nubian populations for S. mansoni. The Kulubnarti population lived about 1,200 years ago, during an era when Nile flooding was at its highest average known height, and archaeological evidence for irrigation is lacking. The Wadi Halfa population lived further south along the Nile, about 1,500 years ago, when the average heights of the river were lower. Archeological evidence indicates that the Wadi Halfa used canal irrigation to sustain multiple crops.
The analysis of tissue samples showed that 25 percent of the Wali Halfi population in the study were infected with S. mansoni, while only 9 percent of the Kulubnarti were infected.
The standing water collected by irrigation canals is particularly favorable to the type of snail that spreads the S. mansoni infection. Another form of the disease, Schistosoma haematobium, is spread by snails that prefer to live in more oxygenated, free-flowing water.
"Previously, it was generally assumed that in ancient populations schistosomiasis was primarily caused by S. haematobium, and that S. mansoni didn't become prevalent until Europeans appeared on the scene and introduced intensive irrigation schemes," Campbell Hibbs says. "That's a sort of Euro-centric view of what's going on in Africa, assuming that more advanced technology is needed to control the elements, and that irrigation conducted in a more traditional way doesn't have a big influence on the environment."
|Contact: Beverly Clark|