Lymphatic filariasis in a hyperendemic region: a ten-year, follow-up panel survey.

The present study is a long-term panel survey of a population living in a previously identified Wuchereria bancrofti-endemic area of Benin. Unexpectedly, a marked decrease in the prevalence of microfilaremia (from 9.4% to 0.48%; P < 0.001) occurred over a 10-year period in the absence of chemotherapy or vector control measures. The percentage of patients with chronic pathology remained stable during the study period. The decrease in the prevalence of parasitemia could not be explained by environmental or sociologic changes in the region, or by differences between the two study populations. These data suggest that the epidemiology of lymphatic filariasis in an endemic region may change independently of recognized modulating factors.