The dynamics of infection and disease in bancroftian filariasis

This study examines the relationship between the dynamic of Wuchereria bancrofti infection and the development of chronic lymphatic disease. Data sets from Pondicherry, south India, and Calcutta are used to estimate the age-specific proportion of the endemic population which has converted from microfilaria positive to amicrofilaraemia, and is assumed to be at risk of disease. For men, but not women, the age-prevalence profile of the estimated population 'at risk' is shown to correspond closely to the observed age-prevalence of chronic lymphatic disease in the same community. For both sexes, and independent of age, approximately 11% of the population at risk eventually develop lymphoedema. These observations suggest that filariasis endemic populations consist of those individuals who remain amicrofilaraemic and asymptomatic, and those who progress through the sequence: uninfected, microfilaraemic, amicrofilaraemic, to develop irreversible obstructive lymphatic pathology.