Clinical epidemiology of bancroftian filariasis: effect of age and gender.

A cross-sectional survey was used to determine the prevalence of disease (n = 6493) and microfilaraemia (n = 24,946) due to Wuchereria bancrofti in Pondicherry, south India. The total disease attributable to filariasis was significantly higher in males (13.67%) than females (2.26%), due to the occurrence of hydrocele in males. While the prevalence of chronic signs was clearly age-dependent in both sexes, that of acute signs was independent of age. Thus the age and gender structure of the survey sample will crucially influence apparent prevalence. Examination of the gender differences in the point prevalence of disease in 12 areas of India showed a significant relationship between occurrence of disease and gender, but this relationship did not significantly differ between northern and southern Indian populations. The study suggested that the failure to appreciate the importance of age and gender in disease prevalence has led to misconception about disease patterns in India.