Mosquitoes now resisting treated nets

The ability of mosquito adaptation has largely limited nets efficacy and effectiveness. [File, Standard]

Treated bed nets are no longer effective in controlling mosquito carrying malaria parasites, according to a 12-year study.

Medical researchers at the Kenya Research Institute (KEMRI) had found that mosquito nets have passed their protective limits against malaria control if their studies in Western Kenya are any yardsticks.

Dr Andrew Githeko, who was part of the experts in the study, said the findings “could have major implications in the war against malaria, not only in Kenya, but in the entire Africa because nets are the primary malaria preventive strategy.”

The study further revealed that the usage of mosquito nets had increased tremendously in the last 25 years, and consequently, malaria prevalence among school going children had decreased by 70 per cent from 2003 to 2015.

However, the study indicated a resurgence by more than 50 per cent from 2015 to 2019 in tandem with the population of anopheles funestus mosquitoes having also increased 30-fold in endemic zones between 2007 and 2019.

The study suggested that though treated nets will be in use in the foreseeable future, the ability of mosquito adaptation has largely limited their efficacy and effectiveness.

The increased insecticide resistance in vectors, together with outdoor transmission, has limited the efficiency of the nets, thus requiring the scaling up efforts of other preventative measures like clearing bushes around homes, destroying stagnant water, taking preventive anti-malarial tablets while travelling to endemic zones and getting immunised.

“The rebounding in the malaria transmission has highlighted the urgent need by stakeholders of new or improved malaria control programmes, and interventions to further reduce transmission in Kenya,” said Dr Githeko.

The research was funded by the US National Institute of Health and carried out by local scientists and those from the University of California, and conducted in Kakamega, Vihiga, Kisumu and Kisii counties.

Several other studies and deliberations on mosquito resistance against insecticides used in treating bed nets and indoor residual spraying have been sponsored by donors, including the World Bank and the World Health Organisation (WHO).

Kenya turned to chemical Malathion for indoor spraying after the vector showed high resistance to DDT, which was used in the war against mosquitoes, but was banned due to its environmental challenges.