Natural infections of Wuchereria bancrofti in Aedes (Stegomyia) polynesiensis and Aedes (Finlaya) samoanus in Samoa

Abstract
Seven years after the 2nd mass treatment of the population with diethylcarbamazine, transmission of subperiodic Wuchereria bancrofti was studied in four villages in Samoa during one year by means of biting catches of Aedes polynesiensis and A. samoanus. 2 villages were coastal, one inland bush and the other an inland coconut plantation community. Overall infection and infective rates from 6702 Ae. polynesiensis were 0·84 and 0·27% respectively, and the infection rate from 2858 Ae. samoanus, collected in 10-minute catches from 24 sites, was 0·65%. No infective Ae. samoanus was found in these samples. 12-hour all-day catches in the 2 coastal villages confirmed active transmission by Ae. polynesiensis. 12-hour all-night catches in the same 2 villages recorded high transmission by Ae. samoanus although there was little evidence of local breeding. The annual transmission potential for Ae. polynesiensis and Ae. samoanus was high in one of the coastal villages and low in the otther. A total of 221 infected Ae. polynesiensis and 40 Ae. samoanus were recorded. Of the 72 infective Ae. polynesiensis, 59·1% contained 1 to 2 larvae each (median density 1·4); 70% of the 40 infected Ae. samoanus had 1 to 2 larvae (median density 1·1). From the proportion of infective Ae. polynesiensis the mean probability of survival was estimated as 0·917.