Late-acting dominant lethal genetic systems and mosquito control

Abstract

Background: Reduction or elimination of vector populations will tend to reduce or eliminate transmission of vector-borne diseases. One potential method for environmentally-friendly, species-specific population control is the Sterile Insect Technique (SIT). SIT has not been widely used against insect disease vectors such as mosquitoes, in part because of various practical difficulties in rearing, sterilization and distribution. Additionally, vector populations with strong density-dependent effects will tend to be resistant to SIT-based control as the population-reducing effect of induced sterility will tend to be offset by reduced density-dependent mortality.

Genetics‐based methods for agricultural insect pest management

“…This sex‐specificity can be exploited to enable male‐only release because removing the repressor from the final generation of insects prior to release results in only males surviving, thus achieving sex‐separation by ‘genetic sexing’. Another novel genetic trait, developed in container‐dwelling mosquito species (Phuc et al ., 2007), has lethality occurring after the immature life stage that is affected by density‐dependent competition mortality and before reaching maturity; adult females are harmful as they bite and transmit disease. Where the juvenile stage of a pest insect causes damage to plants, such a late‐acting trait is less attractive.…”

“…For example, modelling the effects of larval competition and exploring late‐acting lethal phenotypes in mosquitoes predicted that this could be substantially more effective at population control than an early‐acting (e.g. embryonic) lethality or radiation‐induced sterility (Atkinson et al ., 2007; Phuc et al ., 2007; Alphey & Bonsall, 2014a). Indeed, if density‐dependent juvenile competition were over‐compensatory, genetic lethality that occurred at an earlier stage, thereby freeing survivors from regulation by intense competition, could push adult insect numbers higher than in the natural uncontrolled population (Yakob et al ., 2008; Alphey & Bonsall, 2014a).…”

“…The density dependence term in the formula is adjusted according to whether the genetically‐induced mortality occurs before or after the competition takes effect (Alphey & Bonsall, 2014b). Critical thresholds, or tipping points, are a common feature of models of genetic control (e.g., Atkinson et al ., 2007; Phuc et al ., 2007; Alphey et al ., 2009, 2011b; Alphey & Bonsall, 2014a,b). A ‘release ratio’ or ‘overflooding ratio’ can be defined in various ways, such as the ratio of engineered males to the number of wild males at natural equilibrium to be maintained at constant value through sustained ongoing releases balancing out mortality, or as a fixed proportion of released males to males emerging in the wild.…”

“…A key practical result of a mathematical model of genetic control of the mosquito Aedes aegypti (L.) (Phuc et al ., 2007), which transmits viruses including dengue, yellow fever and Zika, suggested that those engineered males would need to achieve 13–57% of matings to achieve sufficient suppression to reduce the disease burden of dengue virus. This model prediction has guided assessment of the performance of the strain in open field trials (Harris et al ., 2011, 2012).…”

Mathematical Modeling of Sterile Insect Technology for Control of Anopheles Mosquito

“…Recently (2007) in Italy, Bellini [10], released sterile males, which contributed to reduce the wild population of aedes albopictus and to fight the Chikungunya virus [17] (see [15,16] for further details about Chikungunya). Furthermore, mosquitos genetically modified by using the RIDL (Release of Insects carrying a Dominant Lethal) Technique, were released in the Caïman Island and in Malaysia, by the Oxitec Company to fight Dengue Fever (see [25] for an overview on RIDL approach for Aedes aegypti ).…”