[ Bancroftian lymphatic filariasis: toward its elimination from the Pacific?]

The region of the Pacific is historically affected by lymphatic filariasis (LF). Following the World Health Assembly resolution in 1997, the Global Program to Eliminate Lymphatic Filariasis (GPELF) was launched. In the Pacific, the World Health Organization (WHO) has implemented from 1999, the Pacific Program to Eliminate Lymphatic Filariasis (PacELF) bringing together the 22 countries and territories, in a common effort to eliminate the disease. The strategy is based on Mass Drug Administration (MDA); in annual single dose during 5 years of a Diethycarbamazine/Albendazole association distributed to all the population at risk. Among the 22 countries and territories of the Pacific, 16 are endemic and 6 are non endemic. The classification is based according to the filarian antigen prevalence upper or lower than 1%. MDA are decided when the rate of the filarian antigen prevalence is > 1%. The objective of PacELF is to reduce this rate down to < 1%, threshold under which the transmission is supposed to be stopped. From 1999 to 2007, 14 of the 16 endemic countries organized MDA. Eleven of them completed the cycle of 5 treatments and even beyond. But, these MDA reached only 19% of the at risk population, because of logistic difficulties in Papua New Guinea, the most populated country in the Pacific. The investigations carried out in sentinel sites showed a public health impact, by the fall of the number of microfilaria carriers, often down to a rate < 1%. However the rate of circulating antigen prevalence remains often above the required threshold of 1%. Prevalence surveys carried out in 2007, in different endemic countries, revealed the necessity to intensify efforts and to refine strategy for elimination of FL from the Pacific. A lot of progress were obtained, but few problems were identified. Reflexions are imperative and in progress about: the MDA coverage rates while at the same time a certain lassitude appears in the populations and among health staff, the methods to evaluate the effectiveness of MDA, the reliability of the diagnostic tools to decide of the stop of MDA and to certify the absence of the transmission, the relevance of univocal biological criteria for the whole Pacific area, the need for an active surveillance during several years after stopping MDA, particularly in the countries affected by the very efficient vector Aedes polynesiensis. Seven years after its launching, despite undeniable success, the PacELF program did not achieve its very ambitious goal of stopping the transmission. Three years before its term, strong efforts have to be done and additional strategies be implemented. However; it is reasonable to expect the prolongation of the program in order to achieve the final objective. Beyond, in some countries, it will be still necessary to ensure a sustained global drug pressure and an active surveillance to prevent the re-emergence of the disease.