A study of bancroftian filariasis on the islands of Batan and Rapu Rapu, Philippines.

The islands of Batan and Rapu Rapu in southeastern Luzon, Philippines, were surveyed for filariasis from November 1984 to May 1985. Microfilariae of Bancroftian filariasis were detected in 10.5% of the people over one year of age. Microfilarial rates and intensity of infection were the same for males and females. The highest rates for both sexes were in the 56- to 60-year-old age group. Aedes poicilius, which breeds in abaca and banana plants, was found to be very anthropophilic, comprising 96.5% of the mosquitoes biting man. This mosquito bites most frequently in the middle of the night. Dissections showed that 1.0% of Ae. poicilius were infective with third-stage larvae, and each infective mosquito contained a mean average of 5.6 larvae.