• Specie survives extremely high temperatures during dry season

The Nigerian Institute of Medical Research (NIMR) has confirmed the detection of a non-native malaria vector, Anopheles stephensi, in Nigeria, raising fresh concerns about emerging challenges to malaria control in the country.

The institute disclosed that the invasive mosquito species, which is not indigenous to Africa, was identified through national entomological surveillance and subsequently confirmed using molecular techniques at NIMR’s laboratories.

Speaking during the December media chat at the institute in Lagos, Director of Research and Head of the Malaria Research Group at NIMR, Dr Adeola Olukosi, explained that samples collected from Gombe State during routine surveillance were morphologically identified as Anopheles stephensi and brought to the institute for confirmatory analysis.

She said molecular sequencing of the ITS2 region showed that several of the samples were indeed the invasive vector, marking the first confirmed detection of the species in the country.

Olukosi described Anopheles stephensi as a highly competent malaria vector known to transmit both Plasmodium falciparum and Plasmodium vivax.
Unlike traditional African malaria vectors, which thrive mainly in rural settings, she noted that the species is adapted to urban, man-made environments, breeding in containers, tanks, and other clean-water systems. Its ability to survive extremely high temperatures during the dry season, when malaria transmission is usually low, she said, poses additional risks for sustained transmission.

She explained that the detection of the invasive mosquito underscores the importance of continuous surveillance, noting that Anopheles stephensi has previously caused significant public health challenges in countries such as Ethiopia, where its presence was initially not recognised. According to her, the species’ genetic background suggests resistance to multiple classes of insecticides, making it particularly difficult to control once established.

Beyond the discovery of the non-native vector, Olukosi reiterated that malaria remains Nigeria’s most persistent public health challenge, with the country carrying the largest absolute burden of malaria globally.

She said Nigeria accounts for about 25 to 31 per cent of global malaria cases and deaths, with Plasmodium falciparum responsible for the most severe infections.

Malaria transmission, she added, remains highly heterogeneous across the country, ranging from perennial transmission in the south to seasonal outbreaks in the north.

She noted that malaria research is a core mandate of NIMR, particularly through its technical support to the National Malaria Elimination Programme (NMEP). According to her, sentinel surveillance and therapeutic efficacy studies coordinated by the institute play a critical role in monitoring the effectiveness of antimalarial drugs and guiding national treatment policies.

Olukosi, a molecular biologist, said that molecular surveillance conducted by NIMR helps predict emerging drug resistance before treatment failure becomes widespread. She disclosed that recent therapeutic efficacy studies conducted across multiple sentinel sites showed that currently recommended antimalarial drugs remain effective, with no immediate need for policy changes.

She also highlighted ongoing research into insecticide resistance, noting that entomological surveillance carried out with NMEP has shown that pyrethroid resistance in Nigerian malaria vectors is widespread and complex. This evidence, she said, has informed the shift towards long-lasting insecticide-treated nets that combine pyrethroids with other insecticides to improve effectiveness.

The researcher added that NIMR’s work extends beyond national borders through participation in regional and global collaborations, including the West African Network for TB, AIDS and Malaria and the Malaria Genomic Epidemiology Network. These partnerships, she said, are critical for tracking malaria evolution and resistance patterns across Africa.

She said the confirmation of Anopheles stephensi in Nigeria reinforces the need for sustained investment in surveillance, research and coordinated response and stressed that malaria elimination efforts in Nigeria must remain evidence-driven to prevent new threats from undermining existing gains.