**4. Paradigm shift, focus and objective**

The introduction of technological innovations—such as the use of *Wolbachia*, the genetic modification of mosquito (GMM) populations, and/or the use of irradiated mosquitoes—that promise better coverage, impact and sustainability propose to improve the effectiveness and durability of control interventions. Nevertheless, the innovations also present organizational and procedural challenges that must be attended before, during and after their introduction

The strategies for genetic and biological control/manipulation with *Wolbachia* of mosquito vectors (GMM/BCMW) propose an attack on the mechanisms directly responsible for the proliferation of mosquito populations. Allowing the mosquitoes' reproductive dynamics be the tool for spreading the intervention means that we will allow the modified populations to disperse naturally (through repeated releases) so that little by little the mosquitoes go about occupying the territory of wild populations to the point of reaching our objective by replacing

The mechanism of dispersion and coverage that is proposed is the male mosquito vector itself; these male mosquitoes will find their female counterparts and transmit the control measure before these females lay their eggs, undiscriminating as to preferred breeding site and location. The progeny (eggs, larvae and adults) will incorporate the intervention naturally and will maintain it in the population that emerges from their lineage (desirable). In essence, the dispersal and upkeep of the intervention will be a product of biological mechanisms rather

Interventions consisting of biological manipulation and genetic control of vectors, furthermore, share many characteristics that again distinguish them from the traditional methods. Among these are as follows: (1) dependence on vertical (maternal) transmission of heritable elements (resistance genes and *Wolbachia*), (2) specificity in regard to affected species, (3) environmental friendliness, (4) harnessing of natural reproductive instincts, (5) noninvasiveness of domestic spaces and (6) large-scale application (indispensable). A common challenge of these innovations and of traditional measures of control is to achieve the coverage necessary

In general, these innovations to vector manipulation are based on two strategies that can be organized according to the results obtained (population elimination vs. replacement) or to the

*Population elimination/suppression*: aimed to affect the demographics of the vector population with the goal of eliminating it from the area or reducing it to a low level that will not maintain

*Population substitution/replacement*: This strategy seeks to replace wild populations with modified populations that are resistant to the viral infection. One of the most novel mechanisms

**3. Innovations to biological and genetic manipulation of** 

them in their function as vectors or by suppressing them as a species.

as control measures.

98 Dengue Fever - a Resilient Threat in the Face of Innovation

**mosquito vectors**

than human intervention.

to be effective and sustainable.

transmission.

implantation dynamics (self-sustainable or self-limiting).

One of the most important changes upon incorporating GMM-BCMW into the *Aedes* and ABD control programs is a *paradigm shift* in passing from emphasis on the larval stages to the direct impact on adult populations. These innovations in *Ae. aegypti* control direct efforts to the reproductive capacity or its competence as a vector, rather than the breeding sites. The theoretical assumption is based on the key elements for vector control centered on adult mosquitoes (abundance, survival, incubation periods, biting rate, etc.) [13]. However, directing control toward adult mosquitoes requires information that is not currently produced in traditional control programs.

Traditional programs of control direct their efforts toward larval stages, reducing breeding sites abundance and the density of larvae in houses and containers, while they attack adult mosquitoes with insecticides that have limited coverage, short duration and low mortality at the population level. The focus and objective of integrated vector management (IVM) are directed to the control of mosquito populations through multi-sector interventions with a multidisciplinary and/or eco-bio-social focus based on changes to community practices, achieved by way of educational interventions.

GMM-BCMW are not technologies that can be used in case of emergency (outbreak control). Focus is directed to the reduction, suppression (elimination) or substitution of *Ae. aegypti* populations; but in all cases, they should be visualized within the IVM scheme as complimentary tools. Traditional vector control programs imposed a strong component of entomological surveillance (larval monitoring) not correlated to epidemiological surveillance (incidence of infection and disease); this favored control responses (reactive) before the increase of entomological indicators, without relating them to transmission risk (risk thresholds). This has resulted in reactive interventions based on detection of an increase in breeding sites or of the number of cases that frequently have late entomological effects but no epidemiological effect. With and IVM approach it is expected to use surveillance as a predictor of risk; the identification of priority areas for interventions and to promote actions before, during and after periods of epidemics. In the case of GMM-BCMW, surveillance should be improved so it can be a powerful (proactive) tool that permits entomological, epidemiological and viral surveillance.
