Wuchereria bancrofti infection and disease in a rural area of Papua New Guinea.

The relation between infection and disease in lymphatic filariasis is still imperfectly understood. This paper presents baseline data on microfilaraemia, oedema and acute episodes from a drug trial against bancroftian filariasis in Papua New Guinea. Among 2,187 people with data on these manifestations, 1,144 were microfilaraemic, 78 had leg oedema, 356 had acute episodes and 919 were negative for all three. All possible combinations of the three manifestations were observed. The relationships between microfilaraemia and disease are found to be time-dependent. Microfilaraemia is a positive risk factor for leg oedema at lower ages, but a negative one at higher ages. Acute disease over a whole year is found to be positively associated with a point estimate of microfilaraemia. However, when considering incidence within a month of the time of the blood sample, a curvilinear relationship is found and people with low but positive microfilarial counts have the lowest incidence. Possible explanations for these findings are discussed.