PAST EXPOSURE AND THE DYNAMICS OF LYMPHATIC FILARIASIS INFECTION IN YOUNG-CHILDREN

This study utilizes parallel, longitudinal entomological and parasitol ogical data collected during a 5-year vector control programme in Pond icherry, South India, to quantify Wuchereria bancrofti transmission fr om the vector to the human population. A simple mathematical model, de rived from the standard catalytic model, is used to examine the hypoth esis that current infection prevalence in young children is a dynamica l function of their cumulative past exposure to infective bites. Maxim um likelihood fits of the model to the observed data indicate a consta nt child infection rate with age, above a threshold representing the p re-patent period, or equivalently, the cumulative biting intensity req uired to produce patent infections. Extrapolation of the model allows the crude estimation of the equilibrium microfilaria age-prevalence cu rve due to control. The results suggest that vector control alone may have little impact on the overall age-prevalence of infection even whe n sustained for long periods. These observations are discussed in term s of the likely impact of density dependent mechanisms, such as acquir ed immunity, on model predictions.