River Blindness: A Success Story under Threat?

he accomplishments of this Programme inspire all of us in public health to dream big dreams. It shows we can reach 'impossible' goals and lighten the burden of millions of the world's poorest people .... " These were the concluding words by former World Health Organization Director-General Gro Harlem Brundtland at the closure ceremony of the Onchocerciasis Control Programme in West Africa (OCP) in December 2002 [1]. The success of the OCP is so undeniable and exemplary, with 600,000 cases of blindness prevented, 18 million children born in areas freed from the risk of blindness, and 25 million hectares of land safe for resettlement, that river blindness is currently considered a disease of the past. This perception nonetheless forgets that OCP covered, at most, 1,200,000 square kilometers to protect 30 million people in 11 countries, leaving a remaining 100 million people in areas where active transmission of onchocerciasis still occurs. After its 28-year fi ght OCP may have won a battle, but a much more diffi cult task lies ahead before we can claim victory against river blindness [2]. Human onchocerciasis is caused by the fi larial parasitic nematode Onchocerca volvulus. Adult worms (macrofi lariae) live in subcutaneous nodules and deeper worm bundles, where fertilized females can produce, during an average of 10 years, millions of microfi lariae responsible for the morbidity associated with the infection. Ingested during a bloodmeal by Simulium (black fl y) vectors, microfi lariae develop within the fl y to infective (L3) stages, that are then transmissible to other people (Figure 1). Many simuliid species have been incriminated to a greater or lesser degree in the transmission of O. volvulus [3], their relative vectorial roles contributing to shape diverse transmission patterns across endemic areas. In Africa, the Simulium damnosum sensu lato (s.l.) species complex, which includes approximately 60 cytoforms, is responsible for more than 95 percent of onchocerciasis cases globally [3,4]. In Latin America, and was imported through the slave trade to six Latin American countries. Previous estimates have placed the number of people infected worldwide at 18 million [7], 99 percent of them in Africa. Since then, the true extent of the disease has been estimated by REMO (rapid epidemiological mapping of onchocerciasis). Villages are selected in each river basin according to appropriate criteria, and levels of endemicity are assessed by onchocercal nodule prevalence in adult host samples [8]. By 2005, more than 22,000 villages …