Mosquito Resistance Threatens Malaria Control in Africa, New Study Warns
A groundbreaking study published in September 2025 reveals a “strong” resistance of mosquitoes to insecticide-treated bed nets in Cameroon, raising alarm bells about the future of malaria control efforts across Africa. The findings suggest a potential reversal of decades of progress in combating one of the world’s most devastating infectious diseases.
According to the World Health Organization (WHO), Africa accounts for approximately 94% of global malaria cases and 95% of deaths. In 2023 alone, the WHO Africa region recorded 246 million cases and 569,000 fatalities. The escalating resistance poses a significant threat to these vulnerable populations.
Cameroon Study Highlights Alarming Trend
Researchers from the Center for Research on Infectious Diseases (CRID) in Yaoundé, Cameroon, and the University of Yaoundé 1, investigated the extent of insecticide resistance in the country, which experiences some of the highest malaria infection and mortality rates globally. The study, conducted between 2020 and 2021, demonstrated that a significant proportion of mosquitoes are now surviving exposure to pyrethroid pesticides – the primary insecticide used in most bed nets.
Mortality rates among mosquitoes exposed to pyrethroid-impregnated nets ranged from 0% to a mere 17% across various locations in Cameroon. “We used the WHO susceptibility bioassay protocol to assess and quantify the level of mosquito resistance,” explained Charles Wondji, lead author of the study and professor of genetics and vector biology at the Liverpool School of Tropical Medicine in England. He further detailed that the standard diagnostic dose of insecticide, intended to eliminate 100% of susceptible mosquitoes, killed less than 20% at some study sites. Even a significantly higher dose proved largely ineffective, with only 10% of mosquitoes succumbing – a level the WHO classifies as “high intensity resistance.”
Continental Crisis Looms
Public health experts warn that the findings represent a critical wake-up call for malaria control programs throughout Africa. A professor of public health biotechnology in Cameroon, who was not involved in the study, cautioned that this resistance could spread rapidly across the region, potentially leading to a widespread resurgence of the disease within years or decades.
The loss of effectiveness of pyrethroid-only nets will inevitably lead to increased mosquito survival rates and, consequently, a higher risk of malaria outbreaks. This will place immense pressure on national control programs, forcing them to urgently adopt alternative interventions to avert a continental crisis. According to one expert, the resistance could have far-reaching repercussions, impacting economic growth, workforce productivity, and healthcare costs.
“If we do not replace these nets in a timely manner, we will undoubtedly face a resurgence of malaria in the years to come, leading to millions of new cases and an increase in deaths,” Wondji warned.
Beyond Bed Nets: The Search for New Solutions
While researchers have not yet definitively linked mosquito resistance to an immediate increase in malaria cases, experts emphasize that the loss of the bed net’s primary function – killing mosquitoes – is a significant cause for concern. Even in the absence of an immediate surge in infections, the potential for future outbreaks remains high.
The study’s authors recommend a shift away from traditional bed nets towards new tools, such as those incorporating piperonyl butoxide (PBO), to combat resistance. However, even this solution may be short-lived, as evidence suggests mosquitoes are also developing resistance to PBO-treated nets, as seen in Uganda, where resistance emerged just three years after their introduction.
Cameroon’s Response and Future Strategies
The National Malaria Control Program (PNLP) in Cameroon has already begun implementing measures to slow the spread of insecticide resistance. Raymond Tabue, a medical entomologist and senior official with the PNLP, explained that mosquitoes exhibit varying reactions to different insecticide classes. He noted that while pyrethroid-only nets were initially effective during mass distribution campaigns in 2011 and 2015, resistance eventually developed.
Efforts to introduce nets treated with alternative chemicals in 2019 also encountered resistance. However, in 2022, the country deployed three types of mosquito nets, including new-generation options like the Interceptor G2. A national campaign is planned for later this year to distribute “new generation” nets combining pyrethroid insecticides and chlorfenapyr. According to the WHO, clinical trials and pilot studies have shown that dual insecticide bed nets improve malaria control by 20 to 50% compared to standard nets.
“The strategy we are currently applying therefore consists of avoiding the use of a single type of insecticide,” Tabue concluded. The ongoing battle against malaria demands a dynamic and adaptable approach, as the mosquito continues to evolve and challenge existing control measures.
