ONCHOCERCIASIS CONTROL PROGRAMME IN THE VOLTA RIVER BASIN AREA

Evaluation, attached to a PES (PD-AAI-383-A1), covers the years 1974-79 and consists of an indepth report prepared by the World Health Organization. Vector control, especially by aerial application of larvicide to the breeding sites, has been highly successful in approximately 75% of the OCP area -- target levels of the annual transmission potential (ATP) (below 100 infective larvae of O. volvulus) and the annual biting rate (ABR) (below 1,000 flies) have been met. Where larviciding has been continuous for 3 years, the disease's incidence among children has been reduced and its symptoms among those already affected stabilized. During certain seasons, larviciding has failed to eradicate vector populations at hydrologically peculiar sites, and vector reinvasion continues to pose a seasonal threat to people at the peripheral zones (20%) of the OCP area. Entomological evaluation teams have produced data on the ABR and the ATP and have plotted the distribution of the principal vectors in the OCP area. The epidemiological evaluation unit has collected data on the disease's clinical, ophthalmological, and epidemiological aspects in over 300 sample areas. Development of new insecticides and drugs has been slow but is accelerating. OCP technical staff, as well as doctors, ophthalmologists, and entomologists from participating countries have received training for institution-building purposes. Participating scientists have received in-service training. Although systematic larviciding on some perennial rivers of the controlled zone's central part has been suspended in the dry season, the Scientific and Technical Advisory Committee concluded that operations must be continued in the OCP area for the scheduled 20 years. Efforts will continue to determine the parasite's longevity in the human host, develop suitable chemotherapy, reduce the impact of reinvasion, and modify control by developing alternative methods and other insecticides. Part two of the report (published separately) details the area's economic development.