A longitudinal study of Bancroftian filariasis in the Nile Delta of Egypt: baseline data and oneyear follow-up

Abstract. We initiated a longitudinal study of Bancroftian filariasis to improve understanding of dynamics and risk factors for infection in villages near Cairo, Egypt. Baseline prevalence rates for microfilaremia and filarial antigenemia for 1,853 subjects more than 9 years of age were 7.7 % and 11.2%, respectively. Microfilaria counts, antigen levels, and microfilaremia incidence over a 1-year period were all significantly lower in older people. These findings 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 recom-binant antigen BmM14, and household infection were all significant risk factors for microfilaremia incidence. Micro-filaria counts and parasite antigen levels were significantly reduced by diethylcarbamazine therapy, but many infected subjects refused treatment, and most treated people were still infected one year later. Incident infections approximately balanced infections lost to produce an apparent state of dynamic equilibrium. Bancroftian filariasis is a major public health problem in the tropics with more than 100 million people infected in 73 countries.1 Filariasis has been endemic in Egypt for centu-ries.2 Although the infection was considered to be almost eliminated and no longer a public health problem in th