Health policy making in developing countries requires estimates of the (global) burden
of disease. At present, most of the available data on schistosomiasis is limited to
numbers of individuals harbouring the infection. We explored the relationship between
the presence of schistosome infection and clinical morbidity, in order to estimate
numbers of individuals with disease-specific morbidity for Schistosoma haematobium
and Schistosoma mansoni infection in sub-Saharan Africa. We searched the literature
for cross-sectional data from field studies reporting both schistosome infection and
morbidity. This was used to derive a functional relationship between morbidity and
infection. After standardisation for diagnostic method, the number of individuals
with specific types of clinical morbidity or pathology was predicted. As only aggregated
prevalences of infection were available for countries or areas, we adjusted for heterogeneity
in infection levels within communities in those countries. In total, 70 million individuals
out of 682 million (2000 estimate) in sub-Saharan Africa were estimated to experience
haematuria in the last 2 weeks associated with S. haematobium infection, and 32 million
dysuria. Ultrasound detected serious consequences of S. haematobium, major bladder
wall pathology and major hydronephrosis, were predicted at 18 and 10 million, respectively.
Infection with S. mansoni was estimated to cause diarrhoea in 0.78 million individuals,
blood in stool in 4.4 million and hepatomegaly in 8.5 million. As the associations
between prevalence of S. mansoni infection and prevalence of diarrhoea and blood in
stool were not very clear, the resulting estimates may be underestimations. Using
the very limited data available, we estimated the mortality rates due to non-functioning
kidney (from S. haematobium) and haematemesis (from S. mansoni) at 150000 and 130000
per year. Given the overall high number of cases with schistosomiasis-related disease
and associated death, we conclude that schistosomiasis remains an important public
health problem in sub-Saharan Africa.