Researchers have developed a new type of bed net with a specific combination of an insecticide and insect growth regulator that could prevent millions of cases of malaria.
The novel net, detailed in the journal The Lancet, contains a pyrethroid insecticide, which repels and kills the mosquitoes, and an insect growth regulator — pyriproxyfen — which shortens the lives of mosquitoes and reduces their ability to reproduce.
Compared to conventional nets, this new type of mosquito net reduced the number of cases of clinical malaria by 12 per cent.
In areas with new combination beds, there was also a 51 per cent reduction in risk of a malaria infective mosquito bite.
Children sleeping under the new bed nets were 52 per cent less likely to be moderately anaemic, which is a major cause of mortality in children under two years, the research showed.
“This new invaluable tool would enable us to tackle more efficiently this terrible and deadly disease that affects many children. If deployed correctly, we could certainly prevent millions of cases and deaths of malaria,” said principal investigator Alfred B. Tiono, from the CNRFP in Africa.
For the study, the team conducted a two-year clinical trial in Burkina Faso, West Africa, involving 2,000 children, aged between six months and five years.
In the trial, the conventional bed nets were replaced over time with the new combination nets in 40 rural clusters covering 91 villages, involving 1,980 children in 2014 and 2,157 in 2015.
A new tool for monitoring bed net use reveals that people don’t use their bed nets consistently, which could contribute to the recent slowdown in progress in the fight against malaria.
More than 400,000 people die from malaria each year, making it one of the world’s deadliest preventable diseases. Insecticide-treated bed nets are widely used to prevent bites from malaria-carrying mosquitoes, and are responsible for preventing an estimated 450 million malaria cases in Africa between 2000 and 2015.
However, the World Health Organization reports that efforts to stop the spread of malaria have stalled since 2015. Bed nets may be losing their effectiveness as mosquitoes adapt their behavior to bite earlier in the day, when people aren’t protected by their bed nets, and gain resistance to common insecticides.
Dr. Paul Krezanoski, lead author of a study published in The American Journal of Tropical Medicine and Hygiene, explored another possibility. He and his research team wanted to know if people actually use their bed nets as recommended – unfurling them around dusk and packing them away after dawn.
However, tracking bed net use can be a challenge. Existing methods are imprecise, like self-reporting, or invasive, like surprise night-time visits to check that nets are in use.
Krezanoski worked with scientists from the Consortium for Affordable Medical Technologies (CAMTech) innovation center in Mbarara, Uganda, to develop a better way to monitor bed net usage. They invented an enhanced bed net called SmartNet, which uses strips of conductive fabric to detect when the net is spread out in use versus folded up and put away.
The researchers recruited 10 families in western Uganda to use the SmartNets as they would any normal bed net for six weeks. The nets recorded whether or not they were in use at 15-minute intervals. Bed net use varied widely from family to family and night to night, and users often neglected to deploy the nets during the hours that mosquitoes were most active. Nets were in use continuously between 6:00 PM and 9:00 AM in less than 10% of cases. Occasionally, they weren’t used at all.
“You would think that if people are being monitored they would use their bed net in a pristine way,” said Krezanoski. “But that’s not what happened, and what that tells me is that there’s probably a whole lot more variation in bed net use than we realize.”
Not only was there variety in when the families unfurled their nets in the evening and put them away in the morning, some families also recorded night-time interruptions. While the reasons for these interruptions aren’t known, the researchers assumed that many were due to childcare duties or using the bathroom.
“I think it’s quite innovative,” said Kate Zinszer, an infectious disease epidemiologist at the Université de Montréal who wasn’t involved in the study. “There is a substantial investment in bed nets and really understanding what actual usage is is a huge gap in current efforts.”
A lingering uncertainty in the study is how being monitored affected the users’ behavior. Krezanoski believes that study subjects would be more careful to use their nets properly than an average person, but others thought they might be less likely. Zawadi Mageni Mboma, a malaria researcher at Ifakara Health Institute who was not involved in the study, said in an email that people’s dislike of being watched or tracked could deter them from using the SmartNets, especially in long-term trials.
Despite that, she added, “Insecticide-treated nets are at the core of malaria intervention. So any information that could further improve the effectiveness is a huge deal for malaria control and elimination.”
The results of the study may also help researchers disentangle the effects of human behavior from other factors, like mosquitoes’ increased insecticide resistance. Ultimately, Krezanoski hopes to be able to show a correlation between how long young children use bed nets and their risk of getting malaria. Krezanoski’s next steps are already underway. He’s part of a research team that will track SmartNet usage, malaria infections and mosquito behavior in 80 households in Uganda.
“I think that will help the international malaria community define exactly how much investment we need to give to bed nets as a whole and also in terms of human behaviors around bed nets, and help us figure out the best ways to reduce malaria going into the future,” he said. (VOA)