Irrigation use can significantly influence the epidemiology of schistosomiasis. The infection is transmitted by aquatic snails, and canal irrigation compounds exposure risk by increasing snail habitat and time spent in contact with contaminated water. In modern populations schistosomiasis has been deemed “the most important water-based disease from a global public-health perspective,” yet little is known about the impact of schistosomiasis on populations living in the past.
To better understand the influence of different forms of irrigation on the burden of schistosomiasis disease in ancient populations, an enzyme-linked immunosorbent assay (ELISA) was used to detect antigens specific to Schistosoma mansoni in desiccated tissue samples from two Nubian populations, one that used saqia canal irrigation (Wadi Halfa, N=46) and one that used annual flooding (Kulubnarti, N=191). Based on evidence regarding the impact of canal irrigation on schistosomiasis prevalence and transmission in modern populations, the prevalence of infection was predicted to be higher in Wadi Halfa than Kulubnarti, peak infection intensity was predicted to occur at an earlier age and at a higher level within the Wadi Halfa population and the prevalence of schistosomiasis to be higher in males than females in both populations.
The prevalence of S. mansoni was greater in the Wadi Halfa population (26.1%) than at Kulubnarti (9.4%)(p=0.002). However, peak prevalence of infection did not occur in a younger age category within the Wadi Halfa population; prevalence of infection peaked at 66.7% in the mature adult age group (46+ years) in the Wadi Halfa population and at16% in the later child age group (6-10 years) in the Kulubnarti population. There were no statistically significant differences in prevalence between males and females of either population.
I also examined the influence of irrigation use and schistosomiasis on the productive capacity of the populations. Using disability estimates from modern populations, the expected reduction in the productive capacity of each population was calculated. The population at Wadi Halfa experienced considerably greater disability of the population due to a higher prevalence of infection; this required a five times greater increase in the productivity of the uninfected population to offset the reduced productivity of infected members.
Monday, October 4, 2010
I submitted the abstract of my dissertation to the department today. This is important both because I needed to write one and because it needed to be submitted two weeks prior to my defense. I got it in a whole day early. Go me. Here it is for your reading pleasure just in case I didn't already ask you to read it and you're not in my department.