Genetic control of Aedes aegypti: data-driven modelling to assess the effect of releasing different life stages and the potential for long-term suppression

Abstract

BackgroundControl of the world’s most important vector-borne viral disease, dengue, is a high priority. A lack of vaccines or effective vector control methods means that novel solutions to disease control are essential. The release of male insects carrying a dominant lethal (RIDL) is one such approach that could be employed to control Aedes aegypti. To maximise the potential of RIDL control, optimum release strategies for transgenic mosquitoes are needed. The use of field data to parameterise models allowing comparisons of the release of different life-stages is presented together with recommendations for effective long-term suppression of a wild Ae. aegypti population.MethodsA compartmental, deterministic model was designed and fitted to data from large-scale pupal mark release recapture (MRR) field experiments to determine the dynamics of a pupal release. Pulsed releases of adults, pupae or a combination of the two were simulated. The relative ability of different release methods to suppress a simulated wild population was examined and methods to maintain long-term suppression of a population explored.ResultsThe pupal model produced a good fit to field data from pupal MRR experiments. Simulations using this model indicated that adult-only releases outperform pupal-only or combined releases when releases are frequent. When releases were less frequent pupal-only or combined releases were a more effective method of distributing the insects. The rate at which pupae eclose and emerge from release devices had a large influence on the relative efficacy of pupal releases. The combined release approach allows long-term suppression to be maintained with smaller low-frequency releases than adult- or pupal-only release methods.ConclusionsMaximising the public health benefits of RIDL-based vector control will involve optimising all stages of the control programme. The release strategy can profoundly affect the outcome of a control effort. Adult-only, pupal-only and combined releases all have relative advantages in certain situations. This study successfully integrates field data with mathematical models to provide insight into which release strategies are best suited to different scenarios. Recommendations on effective approaches to achieve long-term suppression of a wild population using combined releases of adults and pupae are provided.

Control methods against invasive Aedes mosquitoes in Europe: a review

“…Moreover, combined releases of adults and pupae seemed well able to maintain long‐term suppression of a simulated wild population of Ae. aegypti . Field trials have been conducted or are in progress in dengue‐endemic regions .…”

“…Modelling studies have investigated the effectiveness of different control methods such as genetic techniques (e.g. RIDL, SIT), source reduction and/or insecticides, applied alone or in combination . Models have also been used to assess the effectiveness of insecticides in reducing Ae.…”

“…aegypti. 161 Field trials have been conducted or are in progress in dengue-endemic regions. 162 In Brazil, the release of RIDL OX513A males led to the suppression of two target wild populations of Ae.…”

“…Recently, modelling approaches have proved to be very helpful in optimising integrated IMS control strategies by testing several control methods at a theoretical level. 161 Modelling studies have investigated the effectiveness of different control methods such as genetic techniques (e.g. RIDL, SIT), source reduction and/or insecticides, applied alone or in combination.…”

A comprehensive assessment of inbreeding and laboratory adaptation inAedes aegyptimosquitoes

“…Rear and release approaches to arbovirus control require large quantities of mosquitoes to be reared in the laboratory for eventual release into the field. For sterile and incompatible male approaches, high ratios of modified to wild males are needed to achieve suppression, particularly if the modifications have deleterious effects on male fitness [19]. Laboratory environments are inherently artificial, and colonized mosquito populations experience an entirely different set of selective pressures compared to natural populations [20].…”