Microfilarial periodicity of Wuchereria bancrofti in Vanuatu

A study on the relationship between the microfilarial periodicity of Wuchereria bancrofti and vector biting activity was carried out in Penama province, Vanuatu from February to April 1999, to enable the design of a more efficient strategy to control filariasis transmission. The microfilarial periodicities of 22 W. bancrofti antigen-positive volunteers were studied. Microfilariae (mf) were counted every hour for 24 h for 6 volunteers and every hour for 12 h (from 18:00 to 06:00) for 16 volunteers. At the same time as the preparation of mf test slides, indoor human landing catches of the vector mosquito, Anopheles farauti, were conducted to assess the vector biting activity. The time of peak microfilaraemia was 01:32 and the microfilarial periodicity index was 112.3, confirming the nocturnal periodicity of Wuchereria bancrofti in Vanuatu. Nearly all (98.5%) of the mf appeared during the time periods when A. farauti were collected. The timing of vector biting activity corresponded to the time of mf circulation.