BASF's new weapon against insecticide-resistant malaria-carrying mosquitoes

Posted: April 21, 2025

Improved malaria prevention tactics and access to treatments have saved millions of lives worldwide—the World Health Organization (WHO) estimates that 12.7 million malaria deaths have been prevented since the turn of the century.^[1] By January of this year, WHO had certified 45 countries and one territory as malaria-free, including six recent wins: Azerbaijan, Belize, Cabo Verde, Egypt, Georgia and Tajikistan.

However, the tools that helped lead to this success are becoming less effective—mosquitoes are evolving resistance to anti-malarial drugs and the primary recommended insecticide, pyrethroids. In 2023, there were 11 million more malaria cases than in 2022.^[2]

One company that has been tackling insecticide resistance for years is BASF. “Resistance has now been reported in 68 countries. If the fight against malaria is to regain momentum, there is an urgent need to develop and test new tools” explains Achim Reddig, Director of Global Public Health at BASF.

How is malaria controlled?

Malaria control strategies involve multiple angles, including vaccination, timely treatment, and working to control the mosquitoes that spread it. One of the most impactful and scalable interventions in mosquito control is insecticide-treated nets (ITNs). Providing both a physical and a chemical barrier, ITNs reduce the burden of malaria by killing mosquitoes and reducing blood-feeding, which reduces the spread of the disease. More than 3 billion ITNs have been distributed globally since 2004, and 73% of households in sub-Saharan Africa own at least one.^[3]

But developing ITNs is complex. The WHO requires ITNs to last for three years, meaning both the physical net and the insecticide coating must be durable enough to last that long and withstand 20 washes. As they’re designed for people to sleep under, the chemical must also comply with strict safety standards for human exposure, even when ingested—risk assessments include artificial saliva studies to test exposure levels even if a child or infant were to suck the netting that is over their beds.  

Previous generations of ITNs relied on pyrethroids to kill and repel malaria mosquitoes when they came into contact with the net. Pyrethroids work by impeding nerve transmission, killing susceptible mosquitoes quickly. However, resistant mosquitoes survive and reproduce, establishing a larger resistant population over time. Starting in 2017, global recorded cases of malaria began increasing, largely due to resistance to the established insecticides used to prevent the disease.

How BASF's Interceptor G2 combats insecticide-resistance

Described as a “potential game-changer” by the Gates Foundation, one recently approved mosquito-fighting tool is BASF’s Interceptor® G2 (IG2) net. It took eleven years of research and collaboration with IVCC and the London School of Hygiene and Tropical Medicine to develop. The consortium faced several challenges including finding a way to combine two insecticides together, ensuring safety and efficacy, as well as figuring out how to stick the chemicals to the outside of the net.^[4]

After years of lab testing chemicals, the team began using standardized experimental huts to test the new chemical combination. Specially designed entry points enabled mosquitoes to enter the huts but not get out. Volunteers slept in the huts under nets, and the next morning technicians would collect the mosquitoes, tallying how many got in, how many were dead, and how many had fed on blood. The team was pleased to count lots of dead mosquitoes, and statistical analysis suggested that the dual-treated nets would work even better in real life than in the lab tests.

The WHO gave BASF its initial approval for the first-generation Interceptor® long-lasting ITN almost 20 years ago. In March 2023, WHO approved BASF’s IG2 net as a first-in-class, dual-active-ingredient ITN to combat resistant mosquitoes. With IG2, BASF has paired a pyrethroid—alpha-cypermethrin—with chlorfenapyr. Chlorfenapyr works very differently to pyrethroids. It disrupts the insect’s ability to produce energy and transmit the disease. Chlorfenapyr works more slowly as the mosquitoes need to metabolize the chemical, which means the susceptible mosquitoes may still reproduce after sub-lethal exposures. This slows down the selection process for chemical resistance for the next generation of mosquitoes.

^{Source: BASF, Boosting the battle against malaria} 

The BASF team also developed a new textile-finishing process for its multifilament polyester net. Some ITNs incorporate mosquito-killing ingredients directly into the polyethylene fibers of the net itself, which means the nets have regeneration times while the chemicals rise to the surface of the net. The IG2 uses chemicals coated onto the surface, meaning the chemicals are always available to kill mosquitoes that encounter it. The coated nets can be quite stable over time, providing constant protection over three years of use. It also means the nets are odorless, soft to the touch and pleasant to sleep under.

Malaria nets in use

Between 2018 and 2022, a consortium of partners piloted dual insecticide nets as part of the New Nets Project in Tanzania, Benin, and Burkina Faso, aiming to help WHO make its policy recommendation for dual active chemicals in ITNs.

Over four years, the pilot project generated evidence that supported previous hut trial results, showing significant public health value compared to conventional pyrethroid-only ITNs.^[5] Two large-scale cluster randomized control trials conducted in Benin and Tanzania over two years demonstrated that IG2 nets reduced malaria incidence in children aged 6 months to 10 years by 43% when compared to pyrethroid-only nets.

The New Nets Project, which rolled out 56 million dual-ingredient mosquito nets in 17 countries across sub-Saharan Africa, estimates it averted 13 million malaria cases and 24,600 deaths compared to standard nets.

The future of malaria control

The Gates Foundation, which lists malaria eradication as one of its top priorities, has underscored the need for collaboration between organizations, governments, and the private sector to effectively combat malaria. The work of the IVCC, the London School of Hygiene and Tropical Medicine, and BASF in developing the IG2 nets shows what can be achieved with patience and partnership. 

“At an event in Kigali, Rwanda, I heard Philip Welkhoff, Director, Malaria at the Gates Foundation state “We can solve this [malaria]” – this motivates me to continue to invest in innovation to prevent malaria”, Achim Reddig told Our Industrial Life.

With increased adoption of dual-ingredient ITNs slowing down the mosquito population's insecticide resistance, this easily scalable and effective solution is already making a difference. When combined with other new interventions such as vaccination programs, harnessing the power of data to map malaria outbreaks, and genetic editing,  eradicating malaria remains firmly on the horizon.

^{[1] Cases and deaths averted over the period 2000–2023 were calculated by comparing the current annual estimated burden of malaria with the malaria case incidence and mortality rate from 2000, assuming that, as a comparison, they remained constant throughout the same period. World Malaria Report 2024, WHO, page 24
[2] Malaria, WHO
[3]World Malaria Report 2024, pages 74 - 76
[4] Interceptor® G2 - The Challenge, BASF
[5] WHO issues policy recommendation, IVCC}