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Geneva, Switzerland: World Health Organization, Technical Report Series, no. 749. Received 3 August 2000; revised 5 October 2000; acceptedfor publication 10 October 2000 TRANSACTIONS OF THE ROYAL SOCIETY OF TROPICAL MEDICINE AND HYGIENE (2001) 95277-279 Migration and dispersal of lymphatic filariasis in Papua New Guinea N. D. E. Alexander’, M. J. Bockarie’, Z. B. Dimber3, L. Griffin*, J. W. Kazura4 and M. P. Alpers’ ‘Papua New Guinea Institute of Medical Research, P.O. Box 60, Goroka, Papua New Guinea; “Papua New Guinea Institute of Medical Research, I? 0. Box 378, Madang, Papua New Guinea; ‘Papua New Guinea Institute of Medical Research, I? 0. Box 400, Maprik, Papua New Guinea; 4Case Western Reserve Uni- versity School of Medicine, 2109 Adelbert Road, Cleveland, Ohio, USA Keywords: filariasis, migration, Papua New Guinea Lymphatic filariasis is among the 6 diseases which the World Health Organization has recently declared can potentially be eliminated as public health problems (OTTESEN et al., 1997). Reaching this target with the available interventions, notably drugs such as diethyl- carbamazine (DEC), ivermectin and albendazole, which are not totally effective as macrotilaricides, will require widespread and sustained effort. In Papua New Guinea, any community with a single case of lymphoedema or hydrocoele meets the Department of Health’s criterion for inclusion in the mass treatment programme (ANON- YMOUS, 2000). This programme is currently in an assessment phase, determining endemicity. Although successful models are available (BOCKARIE et al., in press), implementation throughout the necessary rural areas will be challenging. Any areas in which control is not maintained could act as reservoirs for dispersal to other parts of the country. Similar phenomena have already been observed in India (SHFURAM et al., 1996), and recognized as a risk in Brazil (BRACCO et al., 1999). The problem could be compounded if tilariasis is not an Address for correspondence: Neal Alexander, Infectious Dis- ease Epidemiology Unit, Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WClE 7HT, UK, fax +44 (0)20 7636 8739, e-mail neal.alexander@lshtm.ac.uk existing well-recognized problem in the destination areas. To investigate the potential magnitude of this phe- nomenon in Papua New Guinea, we analysed migration data from a community-based trial of DEC and iver- mectin in rural parts of the Urat and Urim census districts of East Sepik Province (BOCKARIE et al., 1998). The studv area consists of steeu forested ridges. where most people engage in shifting’subsistence airi: culture, with some cultivation of cash crops. We consid- ered long-distance movements beyond the 2 (East and West) Sepik provinces, a region not linked to the rest of the country by road. In practice, such movements require embarking by sea or air from Wewak, the capital of East Sepik Province, which can be reached from the study area by a partially paved road. Travel to Madang town, the nearest main destination (Figure), takes 5 h by road and 18 h by sea (residents of the study area would invariably travel by sea rather than air). The Table shows such movements which occurred between 1994 and 1997 and lasted for a continuous period of at least 6 months. This type of mobility can reasonably be characterized as ‘permanent or semi- permanent’ and hence as migration (PRESSAT, 1985). Despite the expense and distance, at least 2.5% of the total population out-migrated beyond the Sepik region each year. Common destinations included Morobe, New Britain, the highlands region, National Capital District (NCD), Oro and Madang (Figure). The vast majority of migrants to Morobe went to the provincial capital Lae, while those to New Britain commonly engaged in the oil palm industry. Most (6 1%) of the migrants were male, and the average age was 23 years for males and 22 for females. To quantify the potential transfer of infection, the Table includes the microfilarial status of the 255 (78%) who were tested (by membrane filtration) before any treatment. The overall pre-treatment prevalence was 39%. Since some people did not move until after treatment, this represents the potential transfer, had treatment not occurred. To assess the impact of migration from endemic rural areas to urban settlements, we studied the infection status of migrants, from different parts of the country, living in one hamlet in a squatter settlement located on the outskirts of Madang town. We used the filter naner- based, Wuchereria bakroft-specific, antigen ELISA method (TROPBIO, 1996) to determine infection pre- valence in the hamlet, which had a nonulation of 126 migrants. High population density-and poor-quality makeshift housing characterized the settlement, as they do in other unplanned locations elsewhere in the country