Patterns of epidemiology and control of onchocerciasis in West Africa

Abstract

This paper summarizes the work of the Onchocerciasis Control Programme (OCP) in West Africa, a programme which over a 22 year history has reduced the public health problems of blinding onchocerciasis in eleven countries of West Africa through vector control and, more recently, ivermectin distribution. The paper emphasizes the different approaches to control the programme has developed in the different parts of the programme area which have been determined by the epidemiology of the disease (savanna/forest form), the migratory characteristics of the vectors, intensity of the disease before commencement of treatment, the combined impact of vector control and ivermectin and the likelihood of infiltration of infective blackflies from outside the programme area. The programme has constantly monitored the impact of operations on the trends in prevalence, incidence, annual transmission potential, ocular morbidity and species of fly populations, and as a result, has identified areas where special interventions are required until the programme comes to an end in 2002. The paper illustrates the changes in intensity of infection as measured by community microfilarial load and annual transmission potential over the duration of the programme control activities. The paper also defines and justifies the control strategies in different areas and identifies areas for special interventions.

Nodding syndrome in Mundri county, South Sudan: Environmental, nutritional and infectious factors

“…11 While onchocerciasis is endemic in the three areas in which Nodding Syndrome has been documented (South Sudan, Tanzania, Uganda), O. volvulus is unlikely to be the cause, or sole cause, of Nodding Syndrome given that onchocerciasis is endemic in central and east Africa 83 and was highly prevalent in western Africa before the introduction of vector control. 84,85 While reports of Nodding Syndrome from these areas are lacking, there are clinical descriptions of head dropping/nodding among subjects with epilepsy in onchocerciasis-endemic areas of Liberia 9,10 and western Uganda. 86 These isolated reports, together with the present findings, indicate the need for systematic surveillance for Nodding Syndrome in areas with high endemicity for onchocerciasis.…”

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

“…In all but a small number of treatment zones in the initial areas of the program, vector control was stopped in the late 1980s/early 1990s after detailed epidemiological and entomological assessments (see WHO, 1995;Molyneux, 1995;Boatin et al, 1997;Hougard et al, 2001). However, as OCP evolved into the extension areas in the late 1980s, the anti-helminthic drug ivermectin, which is effective against gastrointestinal helminths in the animal health market, proved to be a potent microfilaricide for Onchocerca infections (subsequently donated by Merck & Co., Inc. [White House Station, NJ], as the drug Mectizan Ò ), and became an integral part of OCP control strategy.…”

“…Monographs for references are by Samba (1994) on the management of OCP; by Remme et al (1986) on epidemiology and modeling; the WHO (1995) Expert Advisory Committee report, which summarized critical aspects of onchocerciasis control; and Remme (1995) who described the development and launch of the African Programme for Onchocerciasis Control (APOC). Molyneux (1995) reviewed the OCP's progress after two decades, and Boatin et al (1997) described the changed epidemiological pattern following extensive control and the expansion of OCP into extension areas. The environmental effects of OCP's control activities has been presented in Resh et al (2004) and Lévêque et al (2003).…”

Beyond Territory and Scarcity: Exploring Conflicts over Natural Resource Management

“…The broad-scale determinants of contemporary land use patterns -vectors of sleeping sickness and river blindness, and colonial forest reservation policy -have resulted in a distinctive settlement pattern in Sekoti in accordance with a cyclical theory of advance and retreat first proposed in the 1960s (Hunter, 1966 andHilton, 1966). In contrast, the more recent changes in forest cover in Biung village have largely been driven by an influx of galamsey (gold) miners since 1995, following the successful control of river blindness (Boatin et al, 1997) The forest reservation policy was shaped by colonial perceptions of 'over-population' and resource degradation, particularly in the north-east corner of the NTs. Similar concerns continue to be raised by some contemporary scholars in Ghana -for example, 'Forest reserves meant to protect watershed and prevent soil erosion are all under serious threat from population pressure' (Nabila, 1997: 78) -and their neo-Malthusian arguments stress (again) 'the need for designing effective resettlement schemes for people from these areas which have far exceeded their carrying capacities' (ibid.…”

“…Initial ground application of DDT was replaced by the aerial spraying of temephos and subsequently the rotational use of insecticides, including Bacillus thuringiensis, permethrin and carbosulfan. In spite of the setbacks due to reinvasion and insecticide resistance (Davies, 1994), onchocerciasis as a disease of public health and an obstacle to development has to a large extent been successfully controlled in northern Ghana (Boatin et al, 1997).…”