Filarial vector studies in a diethylcarbamazine-treated and in untreated villages in Papua New Guinea

Entomological studies were undertaken in three villages in the East Sepik Province of Papua New Guinea. The inhabitants of one village, Nanaha, had been treated with diethylcarbamazine (DEC) to reduce the prevalence and density of microfilaraemia of Wuchereria bancrofti. No intervention was undertaken in the other two villages, Yauatong and Musenau, in which bancroftian filariasis was present but with markedly different human prevalence rates and mean parasite densities. In Yauatong, infection rates in anopheline vectors (Anopheles punctulatus and An. koliensis) varied from 20.5 to 46.6% with infectivity rates of 0-1.4% while these rates were 10.9-14.3% and 0-1.1% respectively in Culex quinquefasciatus. In Nanaha after DEC treatment, infection rates were as high as 16.3% in An. koliensis and infectivity rates reached 7.0% for An. punctulatus despite a 45% reduction in the number of people with detectable microfilariae (mf) and a 94% reduction in mf density in those who remained positive.