Epidemiologic modelling of diseases - a case example using Schistosoma and Trypanosoma

Research to develop dynamic computer simulation models of two host-parasite systems involving Trypanosoma and Schistosoma were initiated in 1986. A knowledge base system for the two parasites was developed from published field data from the tropics. Systems analysis and simulation modelling were applied to describe the quantitative epidemiology of the parasites. Based on mechanistic decomposition of the components of the bio-epidemiologic systems, Forrester's flow diagrams were developed. Interactions between factors in the systems and variables required in the models were estimated from existing data resident in the computer based knowledge base system. Appropriate first order differential equations were set up to describe the dynamics of the models based on mass action theory. Simulation involved integrating birth and death rates, infection and recovery rates and other variables as they relate to population and resource changes, and fluctuations in environmental temperature and rainfall. Both C and FORTRAN languages were utilized in developing the computer models. Simulation studies of several alternatives for the control of the parasitic diseases are now being studied. Ultimately recommendations for the best strategy for the control of the two disease(s) will be provided. It is expected that the methodology developed in this research will be applied to comparable types of processes.