New research into the genetics of\u00a0Anopheles funestus (An. funestus), one of the most neglected but prolific malaria-transmitting mosquitoes in Africa, has revealed how this species is evolving in response to malaria control efforts.<\/p>\n
Reported today (18 September) in\u00a0Science, researchers from the Wellcome Sanger Institute together with leading scientists across Africa sequenced hundreds of\u00a0An. funestus\u00a0mosquitoes collected throughout the continent to explore the genetic variation in the species, including changes driving its adaptation to control methods.<\/p>\n
The results of the study provide a new understanding of\u00a0An. funestus\u00a0that can be used to inform further work towards malaria elimination in sub-Saharan Africa.<\/p>\n
The mosquito species\u00a0An. funestus\u00a0is one of the most widespread in Africa. Females of the species are highly anthropophilic, meaning they are attracted to humans as a source of blood, which they need to develop their eggs. They also have a significantly longer lifespan than other malaria-transmitting mosquito species.\u00a0An. funestus\u00a0is also extraordinarily adaptive. For example, in some areas, it has evolved from biting indoors in the evening to biting outdoors during the day, likely in response to the use of mosquito nets. Together, these characteristics make them formidable malaria transmitters in the part of the world where malaria remains most devastating. In 2023 the World Health Organisation African Region reported 569,000 malaria-related deaths.<\/p>\n
Having a comprehensive understanding of the genetics of each major malaria-transmitting mosquito species is essential for implementing effective malaria control and preventing deaths.<\/p>\n
To support this, mosquito biologists across Africa together with the team at the Sanger Institute collected and sequenced the whole genomes of 656 modern\u00a0An. funestus\u00a0mosquito specimens that were collected from 2014 to 2018. They also sequenced 45 historic specimens from the Natural History Museum in London and the French National Research Institute for Sustainable Development (IRD) that were collected between 1927 and 1967 to understand the evolutionary patterns and changes in the species across 16 African countries during the last century.<\/p>\n
The team found high levels of genetic variation in\u00a0An. funestus\u00a0across Africa and discovered that samples originating from equatorial countries shared many genetic similarities despite covering a 4,000-kilometer range. This suggests that they likely belong to one large, interconnected population. However, some samples from this region, such as those from North Ghana and South Benin, were isolated and genetically distinct from the interconnected population. This shows some populations mix widely, while others remain separate. Such population structure has important implications for mosquito control.<\/p>\n
By looking at the DNA of the historic samples, the team was able to highlight the fast-evolving nature of\u00a0An. funestus.\u00a0One key mutation linked to insecticide resistance, which is widespread among the modern populations, was already present in the mosquitoes from the 1960s. However, other mutations that make mosquitoes resistant to insecticides were absent from the historic mosquitoes, suggesting that these became beneficial for the mosquitoes only later, as different insecticides were used in subsequent decades.<\/p>\n
New biological tools are being used to combat malaria, such as the use of gene drives.\u00a0The team discovered that a key target for a gene drive in\u00a0An. gambiae\u00a0\u2013\u00a0another major malaria-transmitting mosquito species\u00a0\u2013\u00a0is very similar in\u00a0An. funestus. This is encouraging as it suggests that the\u00a0doublesex\u00a0gene drive system developed for\u00a0An. gambiae\u00a0can be adapted to work in\u00a0An. funestus\u00a0as well.<\/p>\n
This new study describes how the genetics of\u00a0An. funestus\u00a0should inform future research and surveillance strategies that aim to reduce the spread of malaria. The data from this study have also been incorporated into the MalariaGEN Vector Observatory that hosts DNA data from multiple\u00a0Anopheles\u00a0species alongside tools for researchers to use in order to analyze data.<\/p>\n
\u201cFor too long\u00a0An. funestus\u00a0has been neglected despite its key role in malaria transmission across Africa. I am thus delighted that this continent-wide whole genome study of the genetic structure of\u00a0An.\u00a0funestus\u00a0is now published. My team is proud to have contributed to this major milestone that will facilitate the implementation of future control interventions against this major vector.\u201d<\/p>\n
– Professor Charles Wondji, author on the paper from the Liverpool School of Tropical Medicine and based at the Centre for Research in Infectious Diseases in Cameroon<\/p>\n
\u201cThe Museum\u2019s collection has been vital for developing methods and providing answers. When asked about why we still develop collections, these sorts of studies remind us that we often just don\u2019t know what we can ask of from our specimens. We need to ensure that the collections are looked after and enhanced ready for whichever high-impact question might come next.\u201d<\/p>\n
– Erica McAlister, Senior Curator at the Natural History Museum<\/p>\n
\u201cWe find some mosquito populations readily sharing variation across the African continent, while others are close neighbors but genetically distinct. This is a challenge for vector control. Even if the Gambiae Complex disappeared today, malaria would still rage through Africa until\u00a0An. funestus\u00a0is also effectively targeted. We hope the greater understanding of the high levels of genetic diversity and the complex population structure we uncover here will underpin smarter surveillance and targeted vector control.\u201d<\/p>\n
– Dr. Mara Lawniczak, senior author and Senior Group Leader at the Wellcome Sanger Institute\u00a0<\/p>\n
Source:<\/p>\n
Wellcome Trust Sanger Institute<\/a><\/p>\n Journal reference:<\/p>\n