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Malaria Prevalence, Indoor Residual Spraying and Insecticide Treated Net Usage in Sub-Saharan Africa

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Gabriel Picone, Robyn Kibler and Bénédicte H. Apouey

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Malaria is transmitted to humans by the bites of certain species of female Anopheles mosquitoes infected with Plasmodium parasites. While there are methods for preventing, detecting and treating this disease, malaria remains one of the principle causes of infant deaths in sub-Saharan Africa. To prevent infection, the Global Malaria Action Plan recommends that inhabitants of affected zones sleep under mosquito nets treated with insecticide. Another strategy in the fight against malaria that has proved effective is indoor residual spraying (IRS) of walls with insecticide. IRS is generally carried out in the context of campaigns run in predetermined zones.

In this article, Picone, Kibler and Apouey test whether IRS campaigns lead to a reduction in the individual use of mosquito nets, and also whether the prevalence of malaria in a residential area has an influence on the use of treated mosquito nets. The individual use of mosquito nets could increase during IRS campaigns in a residential area if inhabitants take the campaigns as a sign of the importance of protecting oneself from malaria. In that case, IRS and the use of mosquito nets would be in complementary relationship. On the other hand, it could be that people see IRS campaigns as sufficient to protect them from malaria and thus make less use of their mosquito nets. In this second case, IRS and mosquito nets would be substitutable goods. In addition, the individual use of mosquito nets might depend on the risk of malarial infection. Economic theory stresses that individual prevention behaviour depends on the prevalence of infection: in other words, individuals adapt their prevention behaviour when the risk of being infected varies. The prevalence elasticity concept captures this link between prevalence and behaviour. If when the prevalence of malaria diminishes, individual use of mosquito nets reduces less than proportionally (weak elasticity, between 0 and 1), then the eradication of the disease will be much less costly than if the reduction in mosquito net use is more than proportional (strong elasticity, greater than 1).

In this article, the prevalence of malaria is measured one to two years before the individual use of mosquito nets, and the specific characteristics of the different zones are taken into account. Moreover, the authors seek to eliminate the possible influence that the communication campaigns can have on individual prevention behaviour, and to correct for possible errors of measurement of prevalence. The data they use combine information on individual prevention behaviour, the socio-economic profile of households, the prevalence of malaria in the area, and rainfall and temperature statistics, for nine sub-Saharan African countries at the beginning of second decade of this century. Analysis shows that IRS and mosquito net use are in complementary relationship. As well, the drop in the prevalence of malaria generates a less than proportional reduction in the use of mosquito nets. If the reduction had been more than proportional, then the task of lowering the risk of malaria infection would have been more onerous. Thus, the results are encouraging for the battle against malaria.

Original title: "Malaria Prevalence, Indoor Residual Spraying and Insecticide Treated Net Usage in Sub-Saharan Africa"
Published in: Journal of African Development
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