THE DEVELOPMENT OF SCHISTOSOMIASIS-MANSONI IN AN IMMUNOLOGICALLY NAIVE IMMIGRANT POPULATION IN MASONGALENI, KENYA

The relocation of several thousand members of the Kamba tribe from the Kyulu Hills to the Thange valley near Masongaleni in Kenya provides a n excellent opportunity to study the development of the immune respons e to schistosomiasis mansoni in a population with little or no previou s experience of the infection. An adjacent, well-established Kamba com munity with similar patterns of water contact provides a suitable ende mic control population. The immigrants were, uniquely, examined shortl y after their arrival in the endemic area, while the prevalence of inf ection was still low. At this time faecal egg counts peaked atypically around 30 years of age. Over the next 12-18 months infection increase d rapidly, especially among teenagers, producing a pattern of infectio n more typical of endemic communities. This substantially narrows esti mates of the time required to develop the important determinants of th e age-intensity profile, supporting the notion that changes related to age per se, rather than duration of infection, dominate. Age-dependen t factors might include behaviour or physiology, including immune resp onse. This paper provides the background for continuing longitudinal s tudies on the development of immunological responses to this parasite.