Transmission dynamics of endemic schistosomiasis

Observations on schistosome infections in a human population, on the occurrence of the intermediate host, and on the exposure of man to infested water in an endemic area in Ethiopia, are brought together. It is observed that there is an apparent lack of correlation between the results of the first type of observation and those of the other two. The relative insensitivity of stool examination methods, the low counts of S. mansoni eggs, and the consequent underestimation of infection rates is discussed along with serologic findings. Finally, it is suggested that schistosomiasis in the area could be described as 'hyperendemic', a situation with a surplus of transmission in which the parasite populations do not seem to be regulated any more by transmission factors.