Bancroftian filariasis and malaria in island and hinterland populations in Sabah, Malaysia

An epidemiological survey of filariasis and malaria in Banggi Island and Upper Kinabatangan, Sabah, revealed microfilarial rates of 7.2% and 8.6% respectively and malaria prevalence of 9.7% and 16.9% respectively. Wuchereria bancrofti was a rural nocturnally periodic type with a periodicity index of 137.2 and average peak hour at 01.32 hrs; 9.2% of microfilaremic carriers as compared to 2.4% amicrofilaremic subjects had clinical filariasis. The Plasmodium falciparum: P. vivax: P. malariae ratios were 1:1:0.17 and 1.4:1:0.12 for Banggi and Upper Kinabatangan respectively. Anopheles flavirostris was incriminated as a new malaria vector in Banggi where the well-known primary malaria vector is An. balabacensis. The latter was also found for the first time to be a vector of rural W. bancrofti in Upper Kinabatangan. Experimental feeding also showed that L3 larvae of W. bancrofti were recovered at low rates from An. balabacensis. Aedes togoi appeared to be a suitable laboratory vector for W. bancrofti.