Africa: Breakthrough – Microbe Found to Block the Transmission of Malaria
Malaria has been a terrible human disease from before the neolithic period up to present day. It has likely caused more human deaths than any other infectious agent. If realised, malaria eradication could be amongst humankind’s most significant achievements.
Malaria is caused by parasites in the genus Plasmodium, of which there are five different species that infect humans. These parasites enter the female Anopheles mosquitoes (males don’t bite humans) when they feed on the blood of an infected human. Plasmodium must then cross the Anopheles mosquito’s gut and become established in their salivary glands, at which point it can be transmitted to another human when the mosquito feeds again.
Globally, the burden of malaria has decreased by about half this century, but in recent years, the rate of malaria gains have slowed and there is a serious risk of biological threats. For instance, some malaria mosquitoes are evolving resistance to insecticides used in bed nets.
The tools currently being used to tackle malaria were developed in the last century, some more than 40 years ago. For example, indoor residual spraying is affected by resistance of mosquitoes, must be repeated at regular intervals and is prohibitively expensive for many African countries.
New tools are desperately needed. I do not mean a silver bullet, just additional entry points that will enable us to simultaneously exert pressure on the malaria transmission cycle from different angles.
For the last five years, my team and I have been studying microbes – tiny microorganisms – that naturally live in Anopheles mosquitoes in Kenya.
We discovered that a microsporidian – a tiny parasitic fungus – called Microsporidia MB can block the transmission of malaria – Plasmodium falciparum – to the mosquito.
We are currently investigating the mechanisms behind the protective effect and have found that the immune systems of mosquitoes with Microsporidia MB are activated.
I believe there is great potential in harnessing the power of microbes that block the transmission of diseases by insects. For instance the Wolbachia bacterium has proved useful in the battle against Dengue fever – another mosquito-borne disease. Wolbachia-based control strategies have the potential to be effective because the bacterium spreads on its own. It will stay in a mosquito population provided it benefits mosquito fitness and can be transferred from mother to offspring.
Our end goal is to find a cost effective strategy to increase Microsporidia MB levels to a point where the Anopheles mosquitoes are no longer able to spread malaria to humans.
We are currently investigating the best way to spread the microbe through mosquito populations. Essentially we want to find out about all the different ways it can be transmitted and then find the best way to “help” it become a mosquito “pandemic”.
