Scientists have discovered a new mosquito species on the coast of Kenya and Tanzania, and they say it is highly resistant to insecticides.

According to researchers from the University of Glasgow, the Wellcome Sanger Institute, and Ifakara Health Institute in Dar es Salaam, it is provisionally named ‘Pwani molecular form’. Their findings were published last week in Molecular Ecology, a leading global peer-reviewed journal. The scientists observe that the new species seems to have developed resistance completely differently and was previously unidentified on the coast of Kenya and Tanzania. The species belongs to the Anopheles gambiae complex, including some of the most deadly malaria vectors.

The new insect presents a fresh headache, because chemical insecticides are at the heart of controlling disease vectors such as mosquitoes. They further add that the new species is restricted to the coastal area of the two neighbouring countries and has massive potential to fuel malaria infection, thereby worsening the disease burden in the East African region. According to the findings, the Pwani molecular form has a unique insecticide resistance profile. Unlike other malaria vectors in the region, it lacks common genetic resistance markers. But how did they make the discovery?

 Technology

According to Sophia Mwinyi, the lead researcher, they deployed the latest technology in genetic sequencing for malaria.

Genetic sequencing in malaria, specifically whole-genome sequencing (WGS), refers to determining the complete DNA sequence of a malaria parasite or a mosquito carrying the parasite. This technology helps researchers understand the parasite’s genetic makeup, including mutations and variations, crucial to studying disease mechanisms, drug resistance, and developing new treatments and vaccines. WGS provides a comprehensive view of the malaria parasite’s genome, allowing scientists to identify genes responsible for its life cycle, such as its ability to infect humans and develop resistance to antimalarial drugs.

WGS can also track how malaria parasites evolve and adapt to new environments, thanks to climate change, including changes in their genetics due to exposure to antimalarial drugs. As a result, Mwinyi explains that their latest findings reveal the presence of a genetically divergent mosquito that could have profound implications for malaria vector surveillance and insecticide-based control strategies in the region.

“The discovery of the Pwani molecular form reveals gaps in our understanding of mosquito diversity in malaria-endemic areas. “Its distinct insecticide profile and restricted geographical presence suggest that this mosquito species possibly plays a potential role in sustaining malaria transmission during the dry season, when other vectors are less active in these respective areas,” Mwinyi observes. She notes this could also explain the persistent malaria cases in these locations, despite the widespread use of bed nets. “By using genetics, we can help stay ahead of the game in the fight against malaria. Understanding the DNA of mosquito populations helps scientists and public health officials design better interventions to stop disease transmission,” says Fredros Okumu from the University of Glasgow and Ifakara Health Institute

Cases

The Ministry of Health’s Public Health and Professional Standards Principal Secretary, Mary Muthoni, highlighted that the latest official data shows Kenya reported about 5.5 million malaria cases in 2023/24, translating into 104 per 1,000 people nationally.

“Our data shows that the top 10 counties with the highest malaria burden accounted for 4,900,664 cases, representing 90.3 per cent of all cases. These counties are Siaya, Busia, Kakamega, Migori, Kisumu, Homa Bay, Bungoma, Turkana, Vihiga and Kwale. Notably, Busia, Siaya, Kakamega, and Migori alone contributed 53.2 per cent of all malaria cases in the country, underscoring the need for intensified interventions in these regions,” PS Muthoni told the Nation a day after World Malaria Day celebration last week.

 Burden areas

She added that the very high-burden areas comprise six counties, namely Busia, Kakamega, Kisumu, Migori, Siaya, and Vihiga, with an average adjusted incidence of 748 malaria cases per 1,000 people, while high-burden counties, including Bungoma, Homa Bay, Kwale, Turkana, and West Pokot, have 474 cases per 1,000 

PS Muthoni said that community health promoters (CHPs) treated 1,097,883 malaria cases at the community level last year. She explained the 2023/24 mass net campaign aimed at distributing 15.3 million nets across 24 counties with support from the Global Fund and USAID/PMI. The campaign achieved 14,627,269 mosquito nets, reaching 4,568,576 households and covering a population of 28,099,563 of the target population. “This is above 80 per cent WHO-recommended long-lasting insecticidal nets coverage in areas at risk of malaria and the minimum threshold to achieve a significant public health impact by reducing malaria transmission,” the PS noted.