Efficient assessment of filariasis endemicity by screening for filarial antigenaemia in a sentinel population.

We have previously reported that a monoclonal antibody-based antigen detection assay (AD12) is sensitive and specific for Bancroftian filariasis in Egypt. The purpose of the present study was to demonstrate the use of this assay in a sentinel population as a means of efficiently screening for filariasis endemicity. Antigen testing was performed with finger-prick blood collected during the day from 743 schoolchildren (ages 11-16 years). The school draws students from 5 villages in Qalubia Governorate, 35 km north-east of Cairo, Egypt. The prevalence of filarial antigenaemia in the school was 17.2%. Antigenaemia rates in children from the 5 villages were 29, 20, 18, 17, and 10% (non-uniformity significant by chi 2 analysis, P = 0.02). These data agree with Ministry of Health rankings of relative endemicity for these villages based on prior night blood surveys. The village with the highest antigen prevalence in children was surveyed one year before the present study. Prevalence rates of antigenaemia and microfilaraemia at that time for a different sample of children aged 11-16 years were 33% and 22%, respectively. We conclude that antigen detection in schoolchildren of this age group is an efficient means of assessing filariasis endemicity in Egypt.