ANTI-VeC awarded 10 pump-primng projects up to £100,000 at the end of last year, the majority of which are now under way.  One of these projects led by Dr Abdoulaye Diabate (IRSS/Centre Muraz) with co-investigators, Dr Etienne Bilgo (IRSS/Centre Muraz), Prof Steve Sinkins and Dr Maria Vittoria Mancini (Glasgow) explores whether Wolbachia confer protection against Metarhizium pathogenic fungi in Aedes aegypti.  In the second of our profiles of awarded projects, we caught up with Dr Abdoulaye Diabate and Dr Etienne Bilgo to find out how the project is progressing.

Briefly describe the project for us?

"This project is combining, for the first time, two promising biocontrol strategies: the intracellular and maternally inherited bacterium Wolbachia, and the mosquito killing fungus Metarhizium for dengue vector control. In this proof of concept study, we want to evaluate the use of Metarhizium to improve the spread of some Wolbachia strains in wild Aedes aegypti populations."

What are the unknowns/gaps in knowledge that you are investigating?

"Wolbachia are common intracellular inherited symbionts in insects. Some strains provide strong protection against pathogens, demonstrate near-complete maternal transmission, and induce cytoplasmic incompatibility (CI) to enable rapid spread into wild mosquito populations, whilst inducing minimal fitness costs. The pathogen transmission blocking properties have brought Wolbachia to the forefront of vector control efforts. The wAu strain transferred into Ae. aegypti produced the strongest transmission-blocking yet observed, but does not induce CI (Ant et al. 2018). Therefore, other ways to spread this strain are needed if it is to be useful for control programs; one possibility is to utilise the selective advantage conferred by protection against entomopathogens deployed as biopesticides. In Burkina Faso, recently isolated local strains of Metarhizium pingshaense are natural enemies of mosquitoes (Bilgo et al., 2018). 

The focus of this proposal is to investigate the possibility that Wolbachia confer protection against Metarhizium pathogenic fungi in Ae. aegypti, and thus assess whether fungi might be used to aid the spread of Wolbachia through populations. Secondly, we will introduce Wolbachia into a Burkina Faso Ae. aegypti line by backcrossing, and carry out a basic characterization of maternal inheritance, cytoplasmic incompatibility, fitness and dengue susceptibility. This will be the first time that Wolbachia have been introduced into an Ae. aegypti genetic background from Africa where there is much greater heterogeneity compared to the globally dispersed form; it is important to establish whether this heterogeneity will impact on the future use of Wolbachia for dengue control in the region."

When did the project begin and what have you explored so far?

"The project started in February 2019. Ae. aegypti were collected from the field in Burkina Faso and a colony was established and maintained in our insectary. This colony has been challenged with Metarhizium fungal infection as well as several insecticide molecules to check its resistance profile to commonly used insecticides. Subsequent genotyping was carried out to characterise the mechanisms of resistance to different classes of insecticides. Two strains of Wolbachia are now being backcrossed into this colony. "

How are you and your partners working together to realise this project?

"The Sinkins group is currently introgressing two Wolbachia strains into the Ae aegypti colony from Burkina Faso. The two Ae aegypti lines will be taken back to Burkina for mosquito lifespan experiments as well as the studies on Wolbachia-Metarhizium interactions."

Is there an example of evidence/data that has surprised you from your experiments so far?

"Preliminary results have shown a surprisingly high insecticide resistance profile in wild Ae aegypti collected in Western Burkina as usual pyrethroids achieved <10% mortality. These alarming results call for additional vector control measures. Interestingly, local isolates of Metarhizium pingshaense showed 100% mortality within 7-8 days post infection against wild Aedes mosquitoes."

What are you hoping the completed project will tell us? 

"A first outcome will be to understand whether and how Wolbachia can provide protection to its host from Metarhizium infection, and whether Metarhizium could be used as a drive system for Wolbachia. This project will also allow a better fundamental understanding of the possible impact of a West African genetic background on Wolbachia including rates of maternal inheritance, CI and dengue susceptibility. This will provide a line that could be used in future dengue control release programs in Burkina Faso. In terms of capacity building, this project will enable scientists from a LMIC country to lead the development and application of this emerging technology for future disease control."

You can hear more about this project from one of its co-investigators Etienne Bilgo at ANTI-VeC’s 2nd annual meeting, where he will be a speaker. Go to our events page for a list of current speakers and to register.

First published: 16 May 2019

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