The impacts of the transgenic mosquito on man and the environment

SILVA, Agnaldo Plácido da. PLÁCIDO, Eloá Jessica Mendes dos Santos. MORAES, Walber Breno de Souza. The impacts of the transgenic mosquito on man and the environment. Revista Científica Multidisciplinar Núcleo do Conhecimento. Year 05, Ed. 10, Vol. 09, pp. 158-176. O c t o b e r 2 0 2 0 . I S S N : 2 4 4 8 0 9 5 9 , A c c e s s L i n k : https://www.nucleodoconhecimento.com.br/biology/transgenic-mosquito, DOI: 10.32749/nucleodoconhecimento.com.br/biology/transgenic-mosquito


INTRODUCTION
Mosquitoes have been intensely studied since the 19th century when they were first related created in several countries, using chemical strategies without restriction of use such as DDT.
And today these measures to control the Aedes aegypti mosquito have been less efficient than when used in the 1950s (WILKE; GOMES et al., 2009). Currently several strategies to control the population of the Aedes aegypti mosquito have been developed, such as risk mapping, natural compounds, Wolbachia, insecticide dispersing mosquitoes, sterile insect technique, transgenic mosquitoes and other (PAN-AMERICAN HEALTH ORGANIZATION, 2019) (ZARA;SANTOS et al., 2016). In the fight against the Aedes aegypti mosquito some types of basic control mechanisms can be used: mechanical, chemical and biological (HOY, 1985) (ZARA; SANTOS et al., 2016).
The genetic strategies that have been developed for vector control are possible to divide them into two stages. The first stage proposes to reduce or even eliminate mosquito species through the development of lethal genes, or capable of making insects sterile, in this technique insects do not require radiation sterilization (POST-PN-360, 2010) (DONOVAN, 2009). In the second stage involves the transformation or replacement of the population, through the introduction of an effector gene to reduce or block the transmission of the disease in the population of wild insects (ARAÚJO; CARVALHO et al., 2015), (ANDRADE; ARAGÃO et al., 2016).  This is a method known as the RIDL system proposed by Thomas that consists of a mechanism in which a dominant lethal gene is associated with a specific promoter of females, such as the calf promoter (WILKE;GOMES et al., 2009) (ALPHEY;BENEDICT et al., 2010).
In this technique, the dominant lethal gene that was introduced into the mosquito can be disabled in the presence of tetracycline. During the separation of male and female mosquitoes, tetracycline is removed from the system, causing the death of all females (OLIVEIRA; CARVALHO and CAPURRO, 2011). The system is blocked when tetracycline exists inside the mosquito, because tTA has more affinity for tetracycline than tetO (ALPHEY, 2002).
Thus, all ridl homozygous males released into the environment will copulate with wild females and all offspring will carry the transgene, in the absence of tetracycline in their diet these mosquitoes will die from toxicity caused by the high levels of tTA in cells (OLIVEIRA; CARVALHO and CAPURRO, 2011) (WILKE;GOMES et al., 2009).

POPULATION REPLACEMENT STRATEGIES
These strategies involve the permanent replacement of a wild population of insects by GM varieties that have been altered in order to make them less capable of transmitting diseases (TERENIUS;MARINOTTI et al., 2008). "This tuning is based on the hypothesis that an increase in frequency in a vector population of a gene that interferes with a pathogen will result in the reduction or elimination of transmission of this pathogen" (COLLINS and JAMES, 1996). This approach consists in the creation of a transgenic insect that is capable of killing, or preventing the replication or dissemination of a specific pathogen, that is, capable of dying once it is infected by the microorganism (TERENIUS; MARINOTTI et al., 2008).
This would happen during the transformation of the cells of a mosquito with a microorganism, which transcribes an inverted-repeated RNA (RNAir) derived from the genome. We can cite as an example the dengue virus type 2, this virus is able to generate a double-tape RNA, which in turn will activate the interference RNA pathway (RNAi), which is able to inhibit the viral The impacts of the transgenic mosquito on man and the environment www.nucleodoconhecimento.com.br cycle preventing the replication of the virus in the mosquito (ADELMAN; SANCHEZ-VARGAS et al., 2002).
In all cases of the creation of GM mosquitoes for release into the environment, it is essential to use sexing technologies, where only males can be released, since they do not feed on blood, such as females, reducing the risk of bites and transmission of diseases (WISE DE VALDEZ;NIMMO et al., 2011).
For David the release of insect GMs should be considered an ecological disturbance whose adverse effects can occur in two phases: in the first occurs a transient phase during which the population of insects including the GMs insects released changes rapidly in density, in the second is the phase of steady state during which the population stabilizes at a constant density (DAVID; KASER et al., 2013).

TRANSITIONAL PHASE
In this phase we can evaluate the evolutionary effects resulting from the transient changes of the gene flow. This gene flow is all the mechanisms that result from the exchange of information and the movement of genes from one population to another, which can occur in gametes or segments of extracellular DNA between populations of the same species, however, some cases of interspecific genetic exchange (WHITTEMORE andSCHAAL, 1991) (SLATKIN, 1985) are known. Where an advantageous gene can act positively by spreading easily in a growing population, when this happens for a long period, one can have the formation of a new species, due to the reduced influence of genetic drift, some of these changes can also move to the steady state phase (GOULD and SCHLIEKELMAN, 2004).
Although gene flow between populations and subspecies may be desired in the case of release of transgenic insects carrying a dominant lethal gene (RIDL), it is necessary to take into account the importance of the effects of gene flow that may be disastrous (GOULD and SCHLIEKELMAN, 2004). For Myers, evolution is not predictable, despite our inability to predict the products of evolution, we can predict significant estimates about evolutionary processes, as they will be affected by the exhaustion of biological diversity (MYERS and KNOLL, 2001). GM insects can alter the evolution of virulence and transmission of a vectorized pathogen, first strains competing within a host can affect virulence and second individual strains transmitted between hosts can lead to a potential exchange between these two levels.
Selection that acts on the parasite's virulence is more complicated when a host can simultaneously harbor several different strains or genotypes of a parasite. In which there is a dominance hierarchy, so that only the most virulent strain in a host is transmitted (MAY and NOWAK, 1995). In ecological systems all living beings interact with other organisms and their environment (PRAKASH;VERMA et al., 2011). This is one of the reasons that make the biological system so difficult to study, are these possibilities of different interactions with organisms and with the environment that makes it so complex (JUNIOR, 2013). We have to take into account that the ecological system can be influenced by hysteresis which is the inability of a system to return to its original state from an alternative state (BEISNER; HAYDON and CUDDINGTON, 2003).
Hysteresis can make it difficult to restore native vegetation in an invaded habitat, such as the removal of invasive plants can increase the number of exotic plants rather than increase the number of native plants in a habitat. The same may happen with the release of GMs insects that may induce an undesirable steady state phase making a reversal impossible (DAVID; The impacts of the transgenic mosquito on man and the environment www.nucleodoconhecimento.com.br KASER et al., 2013).  WHEELER and FALCONA, 2002). In this scenario biology has presented a prominent position in the area of science, mainly in the areas of Molecular Biology and Genetics with transgenic organisms. For this reason, it is of great importance that people be called to reflect and give an opinion on the ethical, moral and social benefits, risks and implications arising from the biotechnologies generated by the research. However, one of the major problems is that the information that people receive does not allow them to appropriate scientific knowledge in order to understand, question them and use them as an instrument of thought, it is possible to verify that there are often intuitive conceptions, strongly influenced by the media, usually devoid of scientific knowledge (ORTEGA; CAPRONI and ROZZATTI, 2011) (PEDRANCINI; CORAZZA-NUNES et al., 2007).
The impacts of the transgenic mosquito on man and the environment www.nucleodoconhecimento.com.br For good or evil, "the trajectory is clear", the introduction of a gene that reduces the fertility of mosquitoes or their ability to transmit a pathogen can be controlled? That's a question that needs to be answered. If something goes wrong, who will take responsibility? How can the damage be repaired? Who should have the authority to introduce this technology into nature? We're talking about eliminating a species or changing its behavior.
In The Science magazine in April 2015 an alert was given by Valentino Gantz and Ethan Bier of the University of California, San Diego. In one of their research, scientists modified a gene, called yellow, of a male of Drosophila melanogaster and performed the crossing of a modified male exempt with a wild female. The mutation that occurred because of this gene altered the staining of the flies, which became clearer. As the alleall was recessive, the females generated from this crossing should be wild, but the male alleall altered the female alleall, and all descendants presented a yellow coloration, eliminating any variation that existed in the insect, or rather, all were the same. If these individuals were released into the environment, all wild insects of the species Drosophila melanogaster would now have this allelo, the problem is that it is not known whether this change occurred in one of the regions of the genome or inserted into an unwanted region of the genome (GANTZ and BIER, 2015).
For Stewart, microorganisms that have been genetically improved have the ability to reproduce and establish themselves as a persistent population that can have subtle and longterm effects on biological communities and natural ecosystems (STEWART JR;RICHARDS and HALFHILL, 2000). DNA modifications may not be limited only to the characteristics of the replaced gene. It is important to take certain care to ensure that when these GM mosquitoes are released into the wild, they do not harm the environment or human health (ANDERSSON; BARTSCH et al., 2006). We can highlight some environmental risks that are likely to occur by the use of Mosquito GMs in the field, because it is of great importance to highlight that each gene can control several different characteristics in a single organism.
Genetic contamination can be seen as a reality, when we introduce gm mosquitoes into a habitat, these mosquitoes can cross with wild or sexually compatible relatives. These new characteristics may disappear or confer a selective advantage to the recipient, altering the relationship and ecological behavior of native species.
The impacts of the ecosystem or the effects of changes on a single species can extend far The impacts of the transgenic mosquito on man and the environment www.nucleodoconhecimento.com.br beyond the ecosystem. Unique impacts are always associated with the risk of damage and destruction of the ecosystem.
The lack of means makes it impossible to monitor these mosquitoes GMs introduced into the environment, with the emergence of some problems, it will be practically impossible to eliminate them.
The horizontal transfer of recombinant genes to other microorganisms is a worrying risk related to mosquitoes GMs, the acquisition of foreign genes by organisms is one of several environmental situations. This can occur especially in response to the change of an environment, providing other organisms, especially prokaryots, which obtained a significant proportion of their genetic diversity through the acquisition of genes sequences of different organisms (OCHMAN; LAWRENCE and GROISMAN , 2000) (MARTIN, 1999), this may confer a new characteristic in another organism, which can be a source of potential damage to people's health or the environment (BENNETT; LIVESEY et al., 2004). It would be a big mistake to assume that recombinant genes in one organism do not spread to other organisms.
The long-term effects of the impact of horizontal transfer of recombinant genes can be relatively strong, this can take thousands of generations for a receiving organism to become the dominant form in a population. In addition, other factors can help. As the appropriate time of biotic or abiotic environmental conditions and additional changes in the receiving organism, may delay adverse effects (NIELSEN and TOWNSEND , 2004). Several scientific evidence has emerged in recent years on genetically modified organisms, showing that there are several clear risks to human health and the environment. When genetic engineers create a transgenic organism they have no way to determine the specific location that will insert the gene. The gene ends up at a random location in the genetic material, and its position is usually not identified (CRAIG;TEPFER et al., 2009) (LABRA;SAVINI et al., 2001). CONCLUSION Researchers have been developing genetic modification techniques at an incredible rate and thereby allowing genes to be found that can control a particular characteristics of an The impacts of the transgenic mosquito on man and the environment www.nucleodoconhecimento.com.br organism. By disparating these genes from the original source and transferring them directly to the cells of an animal, plant, bacteria or virus, offering an exciting possibility for advancement in global pest and disease management, however, the introduction of these genetically modified beings into the environment can bring environmental and ecological consequences. It is of great importance to rigorously evaluate the possible associated risks, providing means and structures to identify possible ecological effects on the evolution of resistance, immunity and transient changes in the interactions of genetically modified insect species. The use of genetically modified organisms is of great importance to meet the growing demands existing on our planet, we are living in a time of anxiety where we want to solve problems, on the one hand we are comforted by threats to health and the human environment, on the other hand, we see new alternatives to change the way things are, so we need vital monitoring and detection methods to assess and manage the risks of using genetically modified organisms. The spread of these transgenic mosquitoes, whose effects, particularly on biodiversity components are difficult to estimate and worse, can be irreversible, causing exposure of species to new pathogens or toxic agents, elimination of non-domesticated species, generation of superpests or genetic pollution among others. Given that these transformations or modifications of living beings in laboratories are new techniques and that so far it is impossible to know what the long-term consequences will be.
And faced with the challenge of finding new alternatives to control a pathogen, scientists have been forgetting one thing, life will always find a way to adapt.