Encephalopathy Related to Ivermectin Treatment of Onchocerciasis in Loa loa Endemic Areas: Operational Considerations

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Human onchocerciasis is a public health problem and an obstacle to socioeconomic development in endemic countries of Africa, Arabian Peninsula and South America (WHO, 1995). The community-directed treatment with ivermectin (CDTI) is the main strategy adopted by the African Programme for Onchocerciasis control (APOC). Severe adverse events with encephalopathy (SAEs) have been associated with mass treatment with ivermectin (Mectizan) in areas where Loa loa and onchocerciasis are co-endemic (Duke, 2003; Twum-Danso, 2003). This has caused wide spread concern on the sustainability of CDTI (Amazigo et al., 2002; Addiss et al., 2003). The most important risk encountered in distributing ivermectin for the control of onchocerciasis in areas where Loa loa is co-endemic is the development of an encephalopathic syndrome. The pathogenesis of Loa loa encephalopathy is not fully understood, but the primary determinant is the level of Loa loa microfilaraemia (Gardon et al., 1997; Boussinesq et al., 1998; Gardon et al., 1999; Boussinesq et al., 2001) and the inflammatory response to the dying worms (McGarry et al., 2003).