Impact of five annual rounds of mass drug administration with diethylcarbamazine and albendazole on Wuchereria bancrofti infection in American Samoa

American Samoa began a territory-wide mass drug administration (MDA) program with diethylcarbamazine and albendazole in 2000 after baseline surveys indicated that 16.5% of 2,989 residents were infected with Wuchereria bancrofti based on tests for circulating filarial antigen. Follow-up surveys were conducted in 2001, 2003, and 2006, using convenience samples of residents of sentinel villages. Antigenemia prevalence in 2001 (11.5%) and 2003 (13.5%) showed no change. After the 2003 sentinel assessment, improvements were made in the social mobilization and drug distribution strategies. In 2006, after a total of 5 years of MDA and 3 years of improved MDA participation, the antigenemia prevalence dropped from 11.5% (2001) to 0.95% (2006) (P < 0.0001). In 2006, antigenemia prevalence was greater in males (1.5%) than females (0.4%) (P = 0.04). The decline in antigenemia prevalence shows the effectiveness of MDA and changes made in social mobilization and drug distribution.