A longitudinal study of Bancroftian filariasis in the Nile Delta of Egypt:Baseline data and one-year follow-up

We initiated a longitudinal study of Bancroftian filariasis to improve unde rstanding of dynamics and risk factors for infection in villages near Cairo , Egypt. Baseline prevalence rates for microfilaremia and filarial antigene mia for 1,853 subjects more than 9 years of age were 7.7% and 11.2%, respec tively. Microfilaria counts, antigen levels, and microfilaremia incidence o ver a 1-year period were all significantly lower in older people. These fin dings suggest that humans develop partial immunity to Wuchereria bancrofti over time. One-year incidence rates for microfilaremia and antigenemia were 1.8% and 3.1%, respectively. Filarial antigenemia, IgG4 antibody to recomb inant antigen BmM14, and household infection were all significant risk fact ors for microfilaremia incidence. Microfilaria counts and parasite antigen levels were significantly reduced by diethylcarbamazine therapy, but many i nfected subjects refused treatment, and most treated people were still infe cted one year later. Incident infections approximately balanced infections lost to produce an apparent state of dynamic equilibrium.