Cumulative exposure and its relationship with chronic filarial disease in bancroftian filariasis

Abstract

Several hypotheses have been put forth about the factors influencing the dynamics of infection and disease in lymphatic filariasis. However, appropriate validation of these hypotheses by real situation analyses of epidemiological data is lacking. The present analyses examine the relationship between cumulative exposure to infection and prevalence of disease by utilizing the existing entomological and clinical data collected between 1981 and 1986 in Pondicherry, South India, endemic for bancroftian filariasis. While there was a significant negative association when the cumulative exposure was correlated with total prevalence of disease (r = 0.70, p = 0.024) as well as hydrocele alone (r = 0.74, p = 0.014), a significant positive association was found with prevalence of lymphedema (r = 0.72, p = 0.018). These results suggest that hydrocele development follows early after exposure, but prolonged exposure could result either in development of lymphedema or immune tolerance resulting in microfilaremia. These could also suggest that the pathomechanisms in development of hydrocele and lymphedema could follow different pathways. Implications of the present findings are discussed in light of the various hypotheses put forward by earlier studies.