Periodicity studies of Brugia malayi in Indonesia: recent findings and a modified classification of the parasite.

We have recently reinvestigated the position of Brugia malayi in Indonesia. Periodicity patterns of microfilariae from several endemic areas were mathematically determined. We have also designed a simple method to quantify microfilaria periodicities in these studies. To determine whether periodicity patterns of microfilariae were stable, repeated studies were performed in the same individual or community. Other biological features of the parasite were also investigated. The parasite from each isolate was taxonomically identified as B. malayi. It could be classified into two distinct biological types, one nocturnally periodic and the other aperiodic, nocturnally subperiodic, or nocturnally periodic. We therefore propose to modify Wilson's classification, using the biological behaviour of the parasite in animals as the discriminating feature, and classify the two types as zoophilic and anthropophilic B. malayi.