**2. Reproduction as a target for vector control**

The interference in insect vector natural populations has remained one of the key strategies for the control of vector-borne diseases. For the past 50 years, vector control policies have relied on the utilization of insecticide-based tools. With the rising of resistance spreading across populations, a major threat to the ongoing success of control programs has been acknowledged [10].

Although insects are the largest and most diverse group of animals on the planet, most species are regarded as species with a high reproductive capacity. Females can generally produce a large number of eggs in a short period, and the high rates of embryo viability boost their natural populations. Blood-feeding (hematophagy) is necessary for most human disease vectors to obtain the energy and nutrients required for efficient oogenesis, enabling the abovementioned high rates of oviposition [11]. Within a vector reproductive cycle, the overall process of converting protein from the blood meal into yolk protein precursors (YPPs), as well as coordinating their delivery to developing oocytes is the most complex stage of reproduction and requires the coordination of intricate metabolic and neuroendocrine pathways in the adult female. As a result, a comprehensive understanding of the complexity of egg production is the most promising approach to designing safe tools for interference in vector reproduction (**Figure 1**).

The molecular physiology of oogenesis is highly conserved within the different insect vectors [11–13]. In brief, oogenesis is triggered by signals from nutritional status and the blood meal. The levels of the sesquiterpene juvenile hormone (JH) [14], secreted by the *corpora allata* in the brain, increase over the early periods of insect maturity triggering changes in the fat body that become sensitive to the ovaryproducing steroid hormone ecdysone [15]. After the blood meal, the brain stops JH synthesis and releases the ovarian ecdysiotropic hormone, signaling to the ovaries to produce ecdysone. In the fat body, ecdysone is hydroxylated to 20-hydroxyecdysone

*Vector Control: Insights Arising from the Post-Genomics Findings on Insects' Reproductive Biology DOI: http://dx.doi.org/10.5772/intechopen.106273*

## **Figure 1.**

*Targets for intervention within the reproductive cycle of vectors. After digestion, adult females are able to lay a large number of highly viable eggs, thus contributing to the increase and maintenance of vector natural populations. The complex physiology process of transforming the contents of the blood meal into mature fertilized eggs requires intricate coordination to accomplish vitellogenesis, delivery of the yolk to the oocytes (yolk uptake), eggshell biogenesis (choriogenesis), and fertilization (mating habits). Interference in any of those stages directly impairs vectors' egg production capacity and embryo viability, rendering drastically reduced reproduction rates.*

(20E) and binds to the 20E receptor EcR/USP to trigger vitellogenesis, that is, the production of the YPPs (yolk protein precursors). YPPs are secreted to the hemolymph and delivered to the developing oocytes in the ovaries via receptor-mediated endocytosis. Apart from the huge metabolic challenge of transforming the blood meal into a large number of eggs, the maximum capacity of egg production is also dependent on successful mating, fertilization, and proper conditions for embryo development [12, 16–23].
