Focally endemic bancroftian filariasis is targeted for elimination in the Nile delta of Egypt. Improved methods are needed for identifying endemic villages to be included in the control programme and for monitoring its success. We have evaluated the performance of a polymerase chain reaction (PCR) assay in estimating Wuchereria bancrofti infection in pools of Culex pipiens (1-25 females) from 2 adjacent villages with high (El Qolzom, 10.8%) and low (Kafr Shorafa, 2.1%) prevalence rates of human filariasis. This assay detects a repeated sequence in W. bancrofti deoxyribonucleic acid (DNA). Mosquitoes resting within houses were captured by aspiration and pooled by house. Houses were classified as positive or negative for human filarial infection based on night blood examinations of residents. The assay detected parasite DNA in mosquitoes from 60% of 25 infected houses and 24% of 25 uninfected houses. PCR processing of mosquitoes caught within houses of unknown filariasis infection status (44 in El Qolzom, 37 in Kafr Shorafa) identified 31.8% and 8.1% of houses, respectively, as containing infected mosquitoes. These results support the validity of the PCR assay for evaluating filarial prevalence in different villages. C. pipiens collected outdoors in dry ice-baited traps and tested by PCR (266 in Qolzom, 82 in Kafr Shorafa) did not contain parasite DNA. Pools of female mosquitoes (296 in Qolzom, 240 in Kafr Shorafa) captured in oviposition traps were also negative. We concluded that the PCR based assay is a powerful epidemiological tool that can be used for evaluating W. bancrofti infection in villages in the Nile delta and for monitoring the application of control programmes in filariasis endemic areas.

We studied effects of combined diethylcarbamazine (DEC) and albendazole (ALB) treatment on Wuchereria bancrofti microfilaria (MF) uptake and development of infective larvae (L3) in Culex pipiens. Consenting Egyptian adults with microfilaremia (MF > 300/mL) were treated with one or seven daily doses of DEC/ALB. Laboratory-reared mosquitoes were fed on subjects before and after treatment. MF uptake and infectivity (assessed by mosquito dissection) were reduced by 89.6% and 82.9%, respectively, 12 months after single-dose treatment and by 96.2% and 99.7%, respectively, after multi-dose treatment. The L3:mosquito ratio decreased by 88% to 0.082 after single-dose treatment and by 99.8% to 0.001 after multi-dose treatment. If high coverage rates can be achieved for several annual cycles, mass drug administration (MDA) with DEC/ALB has the potential to decrease transmission to unsustainable levels and eliminate filariasis in populations. Multi-dose MDA (especially in the first year) might interrupt transmission with fewer cycles than single-dose treatment.