Microfilaria prevalence of diurnally subperiodic Wuchereria bancrofti among people having a medical checkup in American Samoa in the past 17 years.

The yearly change of microfilaria (mf) prevalence rates from 1974 to 1990 was studied in American Samoa with people who had medical checkups. The mf rates were found to have been kept at a low level (0.8-2.6%) in the past 17 years. The continued low prevalence reduced clinical filariasis significantly in the past 8 years. The low level of endemicity, despite very close communication with neighbouring Western Samoa where filariasis is much more prevalent, could be explained by the urbanized living conditions in American Samoa.