Utility of the force of infection model for assessing changes in the dynamics of bancroftian filarial infections.

Force of infection is measured in terms of the number of effective contacts that have been introduced into the population by infective vectors. The utility of such a measure in describing the dynamics of bancroftian filarial infection was tested. Force of infection (beta) incorporating the durations of patent period and pre-patent period was estimated for different age classes (assuming that it is constant in that particular age class) and it was found that the predicted post-control prevalences were close to the observed figures. Utility of Remme's model in areas with different transmission levels is discussed. It was examined whether the empirical function generally used in helminth infections to describe the functional relationship between beta and age could be used for lymphatic filariasis. The relationship between the two was not adequately described by the function. Force of infection, when compared with rate of acquisition calculated using longitudinal data, showed that this measure could be used as a crude estimate of rate of acquisition in places which do not have longitudinal data sets.