Malarial mosquitoes successfully controlled in large cage experiments that mimic natural environments

Polo GGB's large cages for mosquitoes

An international team including Polo GGB researchers have shown that “gene drive” technology is effective at suppressing malaria mosquitoes in complex ecological settings.

 

A year-long experiment led by researcher from the Ecology and Genetics lab of Polo GGB, Imperial College London and Liverpool School of Tropical Medicine have shown the control of Anopheles mosquitoes, the main vector of malaria, in large cage experiments that mimic natural conditions.

This is the first time a gene drive has shown to be successful to suppress mosquito populations in ecologically challenging conditions. The study is published today in the journal Nature Communications.

Evaluation of gene drive mosquitoes in large indoor cages that simulate the natural environment is a critical step of the development pathway suggested by the World Health Organization and the Foundation for the National Institutes of Health to evaluate the efficacy and safety of gene drive technologies in a physically confined laboratory prior to any open field release.

Despite the reduction in malaria over recent decades, there were still 229 million cases of malaria in 2019 – an increase on the previous year – and 409,000 deaths. Novel solutions are needed and gene drive is a very promising technology that can work alongside existing tools such as bed nets, insecticides and vaccines and could be a game-changer in malaria elimination.

The large cages at the Polo GGB facility in Terni, used for the study, contained hundreds of mosquitoes of different ages, representing a more natural and complex population structure compared to previously tested small cages. The cages were also temperature, humidity and light-controlled to simulate sunrise and sunset to encourage mosquito mating in swarms. The cages contained a range of feeding, resting, and egg-laying sites, allowing mosquitoes to exhibit natural foraging, blood-feeding and mating behaviours.

 

Mosquitoes' large cages

The large cages at Polo GGB, Terni, used in the study. © All right reserved – Target Malaria

 

The modified mosquitoes used in the study carried a gene drive that impairs female fertility and ultimately crash the population once the gene drive had spread to all individuals. Modified mosquitoes carrying the gene drive elements were released at initial fractions of 12.5 and 25 percent of the population, and researchers traced how quickly this element spread and its impact on female fertility and eventual population decline.

They found that each of the cages showed a rapid spread of the gene drive and complete population collapse within one year without signs of resistance (no new natural modifications) to counteract the effect of the gene drive.

The results from these studies are a key milestone as they will be used in modelling that aims to predict the spread of a gene drive in specific field sites where these mosquitoes could be released in the future.

 

‘Gene-drive suppression of mosquito populations in large cages as a bridge between lab and field’. by Andrew Hammond, Paola Pollegioni, Tania Persampieri, Ace North, Roxana Minuz, Alessandro Trusso, Alessandro Bucci, Kyros Kyrou, Ioanna Morianou, Alekos Simoni, Tony Nolan, Ruth Müller and Andrea Crisanti is published in Nature Communications 12, 4589 (2021). https://doi.org/10.1038/s41467-021-24790-6

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