BBSRC-funded scientists at the University of Oxford have developed a mathematical model to better understand how to control mosquito populations using a genetic weapon.
The researchers wanted to know how ecology and genetics can influence the effectiveness of a means of control whereby genes harmful to mosquitoes' survival are passed on.
These homing endonuclease genes (HEGs), can insert themselves into DNA across chromosomes, and crucially they can be used to recognise and disrupt DNA that is necessary for an individual mosquito to survive from egg to adult.
Dr Mike Bonsall and DR Nina Alphey developed a mathematical model and report their findings in Journal of the Royal Society Interface.
"One significant finding from our work is that we show that the type of competition affects the outcome of HEG-based control. If competition is particularly strong, alterations in early larval survival could lead to an increase in mosquito population size, rather than its decline,' Dr Bonsall said. "This occurs as the population is 'freed' from its natural ecological control – which in mosquitoes occurs in the late-larval stage.
"We also showed that if a HEG does not just reduce the mosquito's survival, but also changes how that mosquito fares during the larval competition, it could achieve a better reduction in mosquito numbers than an identical HEG that simply reduced survival. The effects of a HEG that affects both survival and timing of competition would need to be carefully monitored to ensure that population suppression is achieved."
Whilst with larger animals it might be possible to monitor individuals as a way of understanding population dynamics this is impractical for populations of thousands of insects, such as mosquitoes, linked to tiny patches of habitat – a small pond or even just a container of water.
Mathematical models are the only practical way of studying the links between genetics and ecology and identifying potential pitfalls in any genetic insect control approach – such as HEGs acting early in an insect's lifecycle being less effective than ones acting later on.
"We are working on extending our modelling approaches to understanding the control of mosquitoes by integrating economics and the cost-effectiveness of control programmes. This involves linking the costs of rearing modified mosquitoes, the epidemiology of the disease, the movement of people and mosquitoes and evaluating the public health benefits," added Dr Alphey.
Dr Bonsall said: 'We hope to work out when and where it might be appropriate to combine these insect control strategies with other disease implementation methods (such as vaccination programmes). Also thinking on how these insect control strategies can be used to control the spread of resistance to conventional control programmes is a new BBSRC project we have very recently started."
Notes to editors
The paper 'Interplay of populations genetics and dynamics in the genetic control of mosquitoes', is published in Journal of the Royal Society Interface, available online at: rsif.royalsocietypublishing.org/content/11/93/20131071.abstract.