Surveys for amoebiasis Interpretation of data and their implications

In survey work, stool microscopy for cysts and serology are the only really practicable measures of amoebic infection. The diagnostic sensitivity of stool microscopy should be estimated. Using a simple deterministic mathematical model, the rates of gain and loss of infection and seropositivity may be estimated from survey data. The low value of the constants creates difficulties but they can be estimated from: (1) cumulative data from frequently sampled cohorts; (2) analysis of the curves of age prevalence; (3) analysis of curves of long-term follow-up studies. The second method is the simplest and normally gives valid results. Appropriate epidemiological studies can give useful information about protective immunity, incubation period, superinfection, and interactions between amoebic infection and various host factors, including other disease states. Knowledge of the rate constants of infection allows predictions to be made about the likely effect of control measures.