The prevalence of Wuchereria bancrofti antigenaemia determined in 353 subjects in Matara, Sri Lanka by Og4C3 ELISA was 20.7%. Positive rates obtained with the same subjects by 1 ml Nuclepore filtration and 60 µl thick blood smear were 11.3% and 7.9%,
respectively. Antigen levels were positively associated with microfilaria counts. Two-thirds of antigen-positive and microfilaria-negative (Ag+/Mf-) individuals were > 25-year-old, but younger age groups (≤ 25-year-old) tended to have proportionally more Ag+/Mf- cases.
Possible origins of the Ag+/Mf- status are discussed.