The mosquito could easily be termed the ‘most dangerous animal in the world’ due to its capacity to act as a carrier for infectious diseases such as malaria, zika, chikungunya and dengue which have deadly effects on human life. Diseases such as these are responsible for the death of over a million people worldwide every year. Currently, it is estimated that nearly half of the world’s population is at risk of malaria. In 2018, there were 228 million reported cases of malarial infection.
Advancements in scientific technology have offered prospective solutions, in varied forms of genetic engineering. In the past few years, these developments have caused much debate. In 2019, an ethical dilemma was presented when researchers successfully genetically modified a fungus to produce toxins normally found in spiders. Theoretically, this modified fungus could be used to completely exterminate mosquitoes. While eliminating mosquitoes as a species would undoubtedly aid the fight against malaria, it would have also lead to a massive loss in biodiversity and thus destabilise the environment. Despite their negative image, mosquitoes, like all species, have a critical role to play in their ecosystems. Continuation of important natural processes like the food chain and pollination are dependent on the existence of the different species of mosquitoes. Moreover, it would be objectionable to intentionally eliminate an entire species simply due to the fact that it poses a threat to humans.
Such impasses are inspiration for further improvement, and the resulting consensus is that rather than killing off mosquitoes, efforts should be focused on halting their ability to carry the parasite. The latest breakthrough lies in the mosquitoes themselves. According to recent research, a symbiotic microbe known as Microsporidia MB, which is found in the gut and genitals of some malaria-carrying Anopheles arabiensis mosquitoes, could be used to limit the transmission of Plasmodium falciparum, the malaria parasite. Researchers have learned that this microbe immunises the mosquito against the malaria parasite by blocking the infection. The association between Microsporidia MB and the mosquito is life-long, thus securing an absolute barrier against infection from the parasite. Theoretically, if all mosquitoes – or at least a high proportion of them – carried this microbe, they wouldn’t be able to pick up and transmit the malaria parasite to humans. Additionally, as the microbe favourably resides in the genitals of the mosquito, it can also be forwarded to new offspring. Taking all these factors into account, this particular discovery seems to have unearthed a hopeful avenue for tackling malaria.
While the existing results show a high success rate in blocking the infection of the malaria parasite; this malaria-blocking microbe was naturally present in only 5% of the mosquito population that was initially investigated. It has been estimated that at least 40% of the mosquito population in a given area must contain Microsporidia MB to achieve a significant drop in malaria infections. This is one of the challenges that scientists are now addressing – what is the most efficient way to infect ‘wild’ mosquitoes with this microbe? Researchers plan to infect more mosquitoes with the microbe and closely monitor them. However, it can be argued that any research is incomplete until it has been successfully replicated in different environments. Presently, the study is being conducted solely in a localised area surrounding the shores of Lake Victoria in Kenya. These trials must be expanded to understand the affinity of Microsporidia MB and Anopheles arabiensis mosquitoes in different parts of the world. It would also be valuable to establish the capacity of other insects to carry malaria in order to prevent the disease from infecting humans.
The need for a solution is clear: malaria is known to be a preventable and curable disease, yet 405,000 people died in 2018 due to malarial infection. Unfortunately, the progress once made by employing preventive measures, in the form of bed nets and insecticides, has stagnated. Another pressing concern is the rapidly building resistance of the malaria parasite, Plasmodium falciparum, against the antimalarial medicines.
The research is only just beginning to explore this particular avenue and although there is still a lot to understand, a potential solution is on the horizon. The symbiotic relationship between Anopheles arabiensis and Microsporidia MB sidesteps the impact that obliterating the mosquito entirely would have had on the ecosystem. This study itself looks promising, but furthermore it paves the way to explore similar relationships that may be present between other species. This research allows for a shift in focus, potentially eradicating the threat of a major infectious disease without threatening the elegant balance of biodiversity.
Written by Simar Mann and edited by Ailie McWhinnie.
Simar’s thoughts… During the COVID-19 pandemic, an anti-malaria drug known as hydroxychloroquine was rumoured to be a promising solution for the coronavirus. There have since been many debates on this matter, which have highlighted the importance of research. Frequently, research proves to have useful purposes beyond those that were first considered, as we are seeing just now with the extensive testing of existing drugs for efficacy against coronavirus. However, it is important to remember that answers and solutions require meticulous hard-work for years and it is the truth for most (if not all) diseases whose cures have yet to be found. With this backdrop, here are a few questions to consider:
What makes a drug a good candidate for COVID-19 treatment?
How can the research process be sped up to find a treatment faster?
Are there examples of drugs being repurposed for malaria treatment?