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Trente ans de lutte contre l’onchocercose en Afrique de l’Ouest. Traitements larvicides et protection de l’environnement

 | 
Laurent Yaméogo
, 
Christian Levêque
, 
Jean-Marc Hougard

Références des articles présentés sur le cédérom / Papers references presented on CD-ROM

Onchocerciasis control by large-scale ivermectin treatment

K. Y. Dadzie, J. Remme, G. De sole, B. Boatin, E. S. Alley, O. Ba, E. S. Alley, O. Ba et E. M. Samba

Texte intégral

  • 1 Aziz MA, Diallo S, Diop IM, Larivière M, Porta M. Efficacy of and tolerance of ivermectin in human (...)
  • 2 De Sole G, Remme J, Awadzi K, et al. Adverse reactions after large scale treatment of onchocercias (...)
  • 3 Dadzie KY, Remme J, Alley ES, De Sole G. Changes in ocular onchocerciasis four and twelve months a (...)
  • 4 Ranme J, Baker RHA, De Sole G, et al. A community trial of ivermectin in the onchocerciasis focus (...)
  • 5 Remme J, De Sole G, Dadzie KY, et al. Large scale use of ivermectin and its epidemiological conseq (...)

1Sir,—Since ivermectin was introduced as a treatment for onchocerciasis1 it has been shown to be applicable for community-based treatment2 and annual application has been found to be effective for the control of onchocercal ocular disease.3 These developments have offered an alternative to vector control in onchocerciasis. However, the effect of annual ivermectin mass treatment in the control of transmission of onchocerciasis is limited4 and large-scale ivermectin treatment, even for “morbidity control”, cannot be achieved quickly.5

  • 6 Remme J, Dadzie KY, Rolland A, Thylefors B. Ocular onchocerciasis and intensity of infection in th (...)
  • 7 Dadzic KY, Remme J, Rolland A, Thylefors B. Ocular onchocerciasis and intensity of infection in th (...)

2The Onchocerciasis Control Programme in West Africa has shown that onchocerciasis can be severely blinding, savanna type6 or mildly blinding, forest type.7 In the savanna, the prevalence of onchocercal blindness increases with increasing community microfilarial load (CMFL) (an index of intensity of infection), and onchocercal blindness starts becoming a public health problem from a CMFL of 10 microfilariae per skinsnip (mf/s). Severely blinding onchocerciasis merits and is receiving control. Further analysis of the programme’s data has revealed that 80% of the onchocercal blind are in communities with a CMFL of 10 mf/s or more or a prevalence of 55% and over, among 15% of the population living in a savanna onchocerciasis-endemic area at high risk of onchocerciasis. Screening communities with a CMFL of 4-10 mf/s or a prevalence of 40-55% increases the pick-up rate to 97% but doubles the population covered to 30% (figure). Onchocercal blindness does not occur in communities with a CMFL below 0,5 mf/s or a prevalence of 20% or less.

Distribution of onchocercal blind and population at risk of infection by endemicity level in savanna areas of Senegal. Guinea, and Mali.

  • 8 De Sole G, Giese J, Keita FM, Remme J. Detailed epidemiological mapping of three onchocerciasis fo (...)

3These findings underline the importance of epidemiological mapping in onchocerciasis endemic areas,8 before starting any ivermectin mass treatment to control onchocerciasis as a public health problem. Such maps identify the areas and communities that need to have a sustained annual treatment, and also identifies communities that willingly accept treatment. Although ivermectin is supplied free of charge, the cost of its delivery cannot be overlooked even with simplified logistics. An efficient delivery strategy is therefore essential to keep costs down to enhance sustainability. These analyses indicate that before ivermectin mass treatment to control onchocerciasis as a public health problem, it should be clear that the activity will have to be long term. Targeting of the treatment is essential to achieve the most cost-effective and sustainable strategy.

4Onchocerciasis Control Programme in West Africa. BP549. Ouagadougou. Burkina Faso

Notes

1 Aziz MA, Diallo S, Diop IM, Larivière M, Porta M. Efficacy of and tolerance of ivermectin in human onchocerciasis. Lancet 1982; ii: 171-73.

2 De Sole G, Remme J, Awadzi K, et al. Adverse reactions after large scale treatment of onchocerciasis with ivermectin: combined results from eight community trials. Bull WHO 1989; 67:707-19.

3 Dadzie KY, Remme J, Alley ES, De Sole G. Changes in ocular onchocerciasis four and twelve months after community-based treatment with ivermectin in a holoendemic onchocerciasis focus. Trans R Soc Trop Med Hyg 1990; 84:103-08.

4 Ranme J, Baker RHA, De Sole G, et al. A community trial of ivermectin in the onchocerciasis focus of Asubende, Ghana I: effect on the microfilarial reservoir and the transmission of Onchocerca volvulus. Trop Med Parasitol 1989; 40: 367-74.

5 Remme J, De Sole G, Dadzie KY, et al. Large scale use of ivermectin and its epidemiological consequences. Acta Leidensia 1990; 59:177-92.

6 Remme J, Dadzie KY, Rolland A, Thylefors B. Ocular onchocerciasis and intensity of infection in the community I: West African savanna. Trop Med Parasitol 1989; 40: 340-47.

7 Dadzic KY, Remme J, Rolland A, Thylefors B. Ocular onchocerciasis and intensity of infection in the community II: West African rainforest foci of the vector Simulium yahense. Trop Med Parasitol 1989; 40: 348-54.

8 De Sole G, Giese J, Keita FM, Remme J. Detailed epidemiological mapping of three onchocerciasis foci in West Africa. Acta Trop 1990; 48:203-13.

Table des illustrations

Légende Distribution of onchocercal blind and population at risk of infection by endemicity level in savanna areas of Senegal. Guinea, and Mali.
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