Control of River Blindness in West Africa: Case History of Biodiversity in a Disease Control Program

Abstract

The elimination of river blindness (onchocerciasis) in West Africa has been one of the most successful public health and economic development programs yet conducted. Control was based on aerial application of insecticides to control the aquatic, larval stages of black flies in the Simulium damnosum complex and distribution of ivermectin-based drugs to reduce incidence of the filarial worm, Onchocerca volvulus, that may ultimately result in blindness. Control efforts were long-term (1974–2003), extensive (with as many as 50,000 km of river miles being treated weekly for 12 years or longer), and far-reaching (distribution of drugs to almost 7 million people in 11 West African countries). The challenges and success of the program were strongly related to biodiversity: the vector S. damnosum is actually a complex of several species and subspecies, which vary in their competence in disease transmission; the filarial worm O. volvulus has different forms that vary in their virulence and incidence of producing blindness in humans; maintenance of the biodiversity of the non-target riverine fauna was a prime concern of both the control program and the donor countries that supported it; the main insecticide used to control the black fly vector was derived from a bacterium Bacillus thuringensis israelensis; and the drug used in controlling the filarial worm was derived from a soil-dwelling Streptomyces fungus. Long-term biomonitoring studies indicate that environmental damage (e.g., loss of sensitive taxa) incurred was reversed when insecticide applications ceased.