Malaria remains a major public health problem in Africa. Researchers are working hard to understand why.
In 2019, approximately 229 million cases of Malaria was recorded worldwide; 409,000 deaths were recorded within the same year in which majority of the victims were children under the age of five. The World Health Organization (WHO) 2019 report indicated that, nineteen countries in sub-Saharan Africa and India accounted for almost 85% of the total number of malaria cases. Six countries alone accounted for more than half of the cases. Nigeria (25%), the Democratic Republic of Congo (12%), Uganda (5%), Côte d’Ivoire, Mozambique, and Niger with 4% each.
In many other African countries, Long Lasting Insecticidal Nets (LLINs) and Indoor Residual Spraying (IRS) are the main preventive measures. However, these mosquito control strategies are braced with the challenge of mosquito resistance to insecticides.
It should be noted that a loss in performance of pyrethroids and piperonyl butoxide (PBO) based nets in a resistant population of “Anopheles funestus s.s. » was recently observed in southern Mozambique. Similarly, a study in West Africa, precisely in Burkina Faso, demonstrated that the increased resistance of “Anopheles gambiae” was related to the low efficacy of pyrethroid-based nets only. A study carried out in Chad in the Central African sub-region on “Anopheles Coluzzii” revealed similar results. Researchers are therefore unanimous in their view that unless this super-resistance is well managed, the gains made in reducing malaria transmission could be compromised. This will have dire consequences.
Using the World Health Organization protocol for resistance assessment, Dr Tchouakui Magellan, a medical entomologist at the Centre for Research in Infectious Diseases (CRID), reported in a recent study in Uganda a high intensity of pyrethroid resistance, resulting in a significant reduction in the performance of long-lasting insecticide-treated nets. The researcher notes that, this reduction in performance was also observed for second generation nets. Molecular analysis revealed a significant over expression of detoxification genes, particularly of the cytochrome P450 family, such as CYP9K1, CYP6P9a and CYP6P9b. However, no association was observed between the expression of these genes and the worsening resistance.
This finding suggests that another resistance mechanism contributes to this increased resistance. Such a high level of pyrethroid resistance in Uganda could have dire consequences for the effectiveness of insecticide-based interventions. Therefore, urgent measures should be taken to prevent the spread of super-resistance in malaria vectors. The major challenge of researchers at CRID is to continue to monitor resistance in other African countries and to conduct further molecular analyses to better elucidate the mechanisms underlying this increased resistance.