Tanzania: Window screens ‘could reduce global malaria burden’

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Window screening helps protect entire domestic spaces from mosquitoes. Copyright: Gerry Killeen

[Nairobi]Mosquito-proofing houses using window screens should be prioritised as a malaria control strategy, with new evidence suggesting it could “reduce the global burden” of the disease, experts say.

Window screening, the covering of windows or roof space with a material which can allow air flow but prevent entry of insects into houses, extends protection from mosquitoes to entire domestic spaces, in contrast to bed nets which only protect the sleeping area, a study says.

The study, which included re-analyses of previously collected data on malaria cases in Dar es Salaam, Tanzania, found that increasing coverage of complete window screening was associated with a reduction in mosquito bites, resulting in malaria cases declining from 28 per cent in 2004 to less than two per cent four years later.

Malaria, which is transmitted through the bites of infected female Anopheles mosquitoes, claimed an estimated 435, 000 lives in 2017, with an estimated 219 million cases worldwide.

The study concludes that mosquito-proofed housing “might deliver far greater effects on vector populations and malaria transmission than previously thought”, even without use of insecticide. It calls for large-scale trials to gather further evidence.

“The findings of this study are strong enough to reduce the global burden of malaria,” says Gerry Killeen, the lead author of the study and a resident guest scientist at the Ifakara Health Institute in Tanzania. But she adds: “[It] will require participation of stakeholders at all levels in the public health, development and industrial sectors.”

According to Killeen, the study, published in the March issue of Lancet Planetary Health, was originally designed to capture the effects of applying biological larvicides to mosquito larval habitats. Researchers monitored malaria infection burden and vector densities at the same time as an unplanned rise in window screening occurred, helping to also evaluate the impact of window screening.

Kiambo Njagi, an entomologist at the Division of Malaria Control in Kenya, tells SciDev.Net: “The study was properly designed and the results have proved that house screening is a good vector control intervention.”

But Njagi adds that further studies are needed to confirm that house screening can cut malaria cases, in order to persuade policymakers to adopt it.

“If we start talking about house screening the way we talk about bed nets, countries in Sub-Saharan Africa may actually benefit. The window screening method will go a long way in supplementing bed nets which are commonly used in Sub-Saharan Africa,” Njagi says.

The relatively high cost of screening could prove a challenge, according to Njagi, who says that additional evidence of the durability of the intervention would be needed to convince policymakers.

Andrew Githeko, chief research officer at the Kenya Medical Research Institute, advises that using a long-lasting insecticide after window screening could help in malaria control. He says: “It is expensive but human life is not cheap either.”

This article was originally published in SciDev.Net

Full study for Reference:

Gerry F. Killeen and others Suppression of malaria vector densities and human infection prevalence associated with scale-up of mosquito-proofed housing in Dar es Salaam, Tanzania: re-analysis of an observational series of parasitological and entomological surveys (The Lancet Planetary Health, 1 March 2019)

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