A mosquito. PHOTO/FILE/COURTESY
Malaria deaths in the country have remained unacceptably high, with a 2024 World Health Organisation report citing at least 43 deaths daily in 2023.
Despite the use of various tools to fight the disease, a section of Ugandan scientists now believe that an ongoing project to breed and introduce genetically modified mosquitoes (GMMs) could be a game changer in reducing the population of malaria-transmitting mosquitoes. But some conservationists are against the new drive, saying it could tamper with nature and pose environmental risks to the country. Currently, the country is relying on prevention drugs, bed nets, and insecticide spraying to fight the malaria parasite and mosquitoes that transmit malaria. Although these methods have been scientifically proven to work, the changing behaviours and nature of mosquitoes and inconsistent use of bed nets and insecticide spraying have seen the country fail to stop the suffering and economic loss associated with malaria. Ms Krystal Birungi, an insect scientist at Target Malaria Project, which is hosted by the Uganda Virus Research Institute (UVRI) in Entebbe, says the country should prepare to embrace GMMs because of their potential benefits in fighting malaria. She says they have already started baseline studies to understand the behaviours and characteristics of wild (normal) mosquitoes before they embark on breeding and introducing GMMs. “What is important to know about our work is that Target Malaria aims to develop a genetically modified mosquito,” Ms Birungi says.
“We are using a gene drive that aims at reducing the mosquito numbers in the wild, thereby interrupting malaria transmission and saving lives.” “Currently, we are in the early stages of baseline studies and are looking at what exists in the wild –how do the mosquitoes that we have behave? What species do we have? How do they mate? How is their seasonality? How do they spread and disperse?” she adds. The scientist says gathering this information is key in deploying any effective method of mosquito control. Information from Target Malaria says the research in Uganda is still in its early stages with a focus on entomological mosquito collections from Islands within Lake Victoria and mainland field sites in Mukono and Kayunga districts. Target Malaria works with partner institutions in Uganda, Mali, Burkina Faso, and Ghana. Information from the website of Target Malaria also indicates that between 2005 and 2025, “Target Malaria will have received a total of $173 million (about Shs636 billion) or an average of $11.5 million (about Shs42 billion) per year in funding to advance research into the use of gene drive for malaria elimination.”
How gene drive works
Ms Birungi says in the gene drive, they have two areas of focus. “First, we're looking at reducing female fertility so the mosquitoes would, instead of producing, say 300 eggs, are only going to lay 10,” she reveals. “Over time, the number of mosquitoes that would spread malaria will reduce. The other one is changing the sex ratio or bias sex ratio. If a mosquito lays 300 eggs, normally 150 will be male and another 150 will be female,” she adds. Female mosquitoes are the ones that bite. “They're the ones that produce the 300 eggs that are going to lay again. So they are the ones that spread malaria. Now, we would like to change it so that of the 300 mosquitoes produced, 295 are male mosquitoes; male mosquitoes don't bite, and they don't spread malaria. But also, it means you have fewer female mosquitoes to lay eggs," she reveals. “So, over time again, the population would reduce. So those are the two things that we're working on as Target Malaria, thereby interrupting that malaria transmission,” she adds.
The 2024 World Health Organisation (WHO) report states that there was an average of 15,945 malaria deaths in Uganda in 2023. There were over 12 million cases of infections, indicating huge amounts spent by individuals and the government on treatment, in addition to work time lost. Mr Charles Ntege, the senior adviser on entomology at the Ministry of Health Malaria Control Programme, says the current tools and approaches have not delivered the desired results. “The tools we have in Uganda today are not enough. We need more innovations and more new tools to fight the mosquitoes. Why? Because we are dealing with mosquitoes which keep changing their behaviour,” he says.
The adviser says they need innovations that would help to control the disease, both the parasite and the vector. “If we can have innovation like the gene drive in mosquito control where it requires less supervision, less funds to implement it. Once you release these male mosquitoes into the public, you don't need to keep monitoring them all the time,” he notes. “You don't need to keep reminding people to sleep under mosquito net that they may forget. This innovation will tremendously bring down the transmission (of malaria), and we shall be moving towards malaria elimination and malaria-free Uganda,” he adds.
Concerns raised
However, some conservationists and a section of the public say the introduction of GMMs would pose risks to the environment and human health. “In science, we talk about the precautionary principle. If you don’t know much about something, you shouldn’t tamper with it,” says Dr Edward Nector Mwavu, an ecologist at Makerere University College of Agriculture and Environment Sciences. “The concern is that we don’t know how these modified genes will react in the organisms that feed on mosquitoes. The genes may cause problems or even change the genetic codes of the organisms that feed on them. We have heard about Covid-19, which is a result of mutation,” he warns. Fish, chicken and wild birds are some of the organisms that feed on mosquitoes, but they are also eaten by man. Other wild organisms that feed on mosquitoes include bats, frogs, and dragonflies. In defence of drive But Ms Birungi defended the drive, saying the current evidence they have indicates that it is “unlikely” that removing the three targeted species of mosquitoes would destabilise the eco-system or harm human health. “We have about 3,400 species of mosquitoes, and we're only targeting the three that spread malaria (Anopheles coluzzi, Anopheles gambiae and Anopheles arabiansis),” she notes. “So it is unlikely that that (destabilisation of the ecosystem) will happen, and we don't take the concern lightly,” she adds.
Ms Birungi also says in their research partnership, the University of Ghana's entire job is to look at the ecology of the mosquito: What is in the breeding places?
“Even here, when we go to do the baseline study and we collect mosquitoes, we check what is in the water that these mosquitoes are growing up in. What could be feeding on the mosquito larvae? Do mosquitoes pollinate anything?” she explains.“So what I can say is that at the moment, we haven't really found anything that feeds only on mosquitoes. So, it's more like the difference between a food chain and a food web. For example, you may enjoy rice a lot. If today rice was no longer there, you would just eat posho, and you wouldn't die.”
The Target Malaria scientist also argues that the biomass (total mass) of a mosquito is so small that if one had just one species removed, the chances of a catastrophic event are quite low. “But that would be theoretically speaking. However, since there's been research done and it will be published soon before you know, it goes through peer review. So this information will be available. If we get the final issue, nothing unsafe will be released,” she notes. “We work with the regulatory agencies, so those people also have to be convinced before the mosquitoes are released.”
Genetically modified mosquito agenda
1. There are about 3400 species of wild mosquitoes. Only three species that spread malaria are being targeted for genetic modification to reduce their population and stem malaria transmission. The targeted species are Anopheles coluzzi, Anopheles gambiae and Anopheles arabiensis.
2. To achieve the population reduction, the scientists want to reduce the fertility of female mosquitoes and change the sex ratio of male and female mosquitoes hatched.
3. Scientists want to reduce female fertility in that instead of a female mosquito laying 300 eggs, it is made to lay only 10.
4. Scientists want to change the sex ratio in that if a mosquito lays 300 eggs, normally 150 will be male and another 150 will be female, but they want to change it to hatch 295 male mosquitoes and five females. Female mosquitoes are targeted because they are the ones that bite, transmit malaria and also lay eggs to sustain their population.
5. The overall goal is to reduce the population of mosquitoes that transmit malaria, hence eliminating malaria.
