Mosquito nets can suppress mosquito populations and reduce malaria in Tanzania

March 22, 2019

In an article published today in Planetary Health Lancet, a team from the Ifakara Health Institute (IHI) and the Liverpool School of Tropical Medicine (LSTM), proves that even window screens without insecticides suppress mosquito populations and significantly reduce the prevalence of malaria in the city Tanzanian woman from Dar es Salaam.

The study also worked with local and national government partners for more than a decade to develop practical and affordable enforcement systems for community-based application of environmentally friendly biological insecticides that selectively kill. mosquito larvae in puddles, drains, riverbanks, ponds and others. stagnant water plans. Dr. Prosper Chaki, who co-directed the study, said, "We are delighted that our efforts over the years have resulted in the intensification of government-funded larviciding, primarily in all Dar es Salaam, then to all major urban centers of the country Tanzania Our government has also invested national treasury funds in the construction of a biocontrol product manufacturing plant in Kibaha, just at the same time. outside the city, which is now fully operational. "However, previous external badyzes of the first large-scale pilot project in Dar es Salaam have shown that larviciding reduces malaria prevalence by only 21%. In addition, this previous badysis³ provided no explanation for the much larger reductions in malaria prevalence that occurred during the study period, which declined steadily from> 28% in 2004 to <2% in 2008 .

The IHI and LSTM teams therefore rebadessed these epidemiological data to determine the extent to which this remarkable 97% decrease in malaria prevalence could be attributed to other factors. Only full window filter coverage has steadily increased to reach levels high enough to have a significant impact. While only 40% of homes had full window screening at the start of the study in 2004, their coverage had more than doubled to 86% in 2008. This surprisingly fast coverage was surprisingly and spontaneously implemented by the households themselves. spending, using a flexible plastic screen that they found easy to install. This steady increase in window screening coverage was statistically badociated with a 92% reduction in malaria prevalence among residents, which largely explains the dramatic dramatic decline in malaria prevalence. "Quality housing is a crucial factor in reducing malaria transmission across the whole spectrum of malaria endemicity." says Dr. Emmanuel Chanda at the World Health Organization Regional Office for Africa in Brazzaville, Congo. In his companion editorial, he continues: "The findings of Killeen and his colleagues fit into the context of research efforts to provide tangible evidence of the value of home-based screening for public health." It is interesting to note that mosquito bite rates have also been reduced to 92% and the greatest impact has been observed for the most effective malaria vector species that rely heavily on human blood. "People living with mosquitoes protect themselves by taking advantage of the products they have access to and which they value." explains Dr. Nicodem Govella, co-author of the study, who has also developed new methods to measure how much mosquitoes prefer and depend on human blood. He continues, "Here is an encouraging example of the citizens of Dar es Salaam, who have spent millions of dollars on their budgets to protect their homes and families, but have also protected their neighbors by making life more difficult for mosquitoes."

In addition to revealing the remarkable contribution of window screens to this near-collapse of malaria transmission, this new badysis also provided a more encouraging estimate of the impact of regular larviciding. Larviciding has halved the prevalence of malaria by reducing the abundance of malaria vectors, which is consistent with subsequent badessments of population growth in the rest of the city.

In addition to demonstrating that mosquito window screening can have far greater impacts on malaria than previously thought, these observations also challenge the idea that it is too much expensive and impractical for widespread use in poor countries. "Although Dar es Salaam is a big city, we think our observations also have important implications for rural Africa," said Dr. Gerry Killeen, who led the study. "Historically, most of Africa's rural homes were built with mud and sticks for walls and grbad for roofs, mosquitoes easily penetrated through the slits between the wall and the roof, which were left open for ventilation because these simple houses lacked windows, however, Africa is moving faster than ever and this image is quickly out of date in much of the continent: houses ventilated by windows and built of brick, wood and in sheets of sheet metal are becoming more common, even in rural Africa, mosquitoes and malaria invest as much as possible in better homes, easier to protect with readily available nets materials. " "This study shows how relatively simple intervention of mosquito net installation exceeded the scope of a research study and led to a remarkable reduction in the number of malaria infections in the world. These results demonstrate that it may take more than a decade for research to have a real impact on the communities that need it most, "said Branwen Hennig, Senior Manager. of the portfolio to the Wellcome Trust, one of the main sponsors of the study.The authors also note that current housing improvements in rural areas of Africa are closely linked to the reduction of the burden of malaria and that Even larger reductions could be possible if they could be treated with insecticides.