1 Department of Biological Sciences, University of Warwick, Coventry, United Kingdom; Centre for the Epidemiology of Infectious Disease, Department of Zoology, University of Oxford, Oxford, United Kingdom
This paper uses preliminary mathematical models to examine how the dynamic relationship between schistosomiasis infection and disease is altered by chemotherapy. Two types of morbidity are examined: an acute form that is proportional to current infection intensity and that resolves after treatment, and a chronic form that represents accumulated experience of infection and that does not resolve after treatment, or resolves according to some delay function. The analyses indicate that nonlinearities in the age and frequency distributions of infection intensity have a marked impact on the patterns of morbidity. They also suggest that treatment close to the age of maximum infection intensity (i.e., children of schoolage) is most effective in controlling morbidity in the community as a whole. These models are preliminary, and their further development to include more realistic assumptions in relation to field data is discussed.
Authors' addresses: G. F. Medley, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom. D. A. P. Bundy, Centre for the Epidemiology of Infectious Disease, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, United Kingdom.