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By Ing. Agr. Ms. Sc. Javier Souza Casadinho
Housing conditions, sanitary infrastructure and environmental sanitation are important factors in the living conditions and reproduction of insects and therefore must be taken into account in management strategies. Any measure may be ineffective if a substantial reduction in poverty conditions is not achieved together with a continuous and permanent evaluation of both the process put in place and the monitoring of the disease.
To a greater or lesser extent, the media have echoed the dengue epidemic (1) that is ravaging our country. However, beyond listing the cases by province and the consequences on health, the practices of eliminating domestic water sources and on the advance of fumigations, little goes into the causes of this phenomenon and what is more important about the consequences. that massive spraying can have on the health of communities affected by dengue and by such spraying, most of the time carried out in an unscrupulous way, that is without taking into account the environment where they are carried out.
1- What can be the causes of the spread of the disease?
The causes are multiple but interrelated. As is known, the progress of the disease has to do with the expansion of the distribution zones and the survival possibilities of the Aedes aegypty mosquito, both are related to the current agricultural model and climate change, these in turn are linked to each other .
Although it is possible to speak of the multi-causality of diseases, it is undoubted that the productive model based on the monoculture of transgenic soybean, the use of herbicides, fungicides and insecticides has its impact on the reproduction rate and survival of the vector.
In the first place, the deforestation and burning of forests and mountains, to dedicate the land to soybean cultivation, has determined the migration of mosquitoes to other areas where they have found optimal conditions for their survival. In this case, climate change also has a notable influence, especially the rise in temperatures and changes in humidity conditions.
Embryonic eggs can withstand extreme temperatures, remaining viable between 7 months to a year (Almirón, W, 2006) (2).
Given that monocultures are unsustainable in themselves, they require the increasing use of insecticides and herbicides with which they not only impact the survival of insects but also that of their natural enemies.
2- How is the use of pesticides related to the survival conditions of the insect?
On the one hand, the use of pesticides, especially insecticides 2, 4 D and Glyphosate, and insecticides such as Endosulfan, impact on the development of natural enemies of mosquitoes, in this case toads and fish that eat both larvae and adult insects. . These pesticides can directly impact as well as cause alterations in their embryonic development (3) and in the nervous system, altering their chances of survival. There is even research on alterations in the immune system of these animals related to the increase in the concentration of pesticides in the water of rivers, ponds and lagoons. In this case, this immunological alteration makes them more vulnerable to bacteria and parasites.
A study carried out on water courses in the province of Buenos Aires (Agostini, 2005) (4) has verified the impact of pesticide mixtures on the survival of amphibians. Especially important are the effects on the initial stages of the life of these organisms, larval stage. The non-lethal impact can have consequences on the growth and development conditions of these organisms.
On the other hand, the increase in the frequency of application as well as in the doses of these products determines the appearance of genetic resistance. In this way, the more chemicals used, the more resistance the insects acquire. Resistance that is transmitted to future generations of the insect. This resistance can have a double modality:
a- the ability of the insect to detoxify - break, unfold - the pesticide molecule transforming it into a less dangerous substance and
b- the possibility of generating a harder exoskeleton –external protection from insects– which makes it more difficult for the pesticide to penetrate the body. In both cases, and following the Darwinian conception, that the fittest survive, in a few generations all mosquitoes develop resistance. In this situation the normal doses of the pesticide become ineffective. By generating the increase in the doses, the replacement by more toxic products and even the increase in the frequency of application; they only reinforce the problem.
3- Is the expansion of the mosquito's distribution area related to climate change?
It can be said that yes. The climatic change that manifests itself from a rise in temperature and humidity conditions have led to both the expansion of the distribution area and the increase in the number of annual generations of the mosquito and therefore better conditions for the expansion of the mosquito. disease. However, climate change has not occurred naturally or by chance, on the contrary it is related both to the increase in industrial activities, transportation, the burning of forests that generate carbon dioxide and to the decrease in the area covered by trees, that absorb that compound. Again we find a relationship between the agricultural production model and the spread of the disease.
4- Is the use of pesticides effective to reduce mosquito populations?
Experience shows that used in isolation they do not solve the problem. First of all, it must be taken into account that vector-borne diseases are influenced by multiple elements and that focusing control strategies on the chemical attack of the vector is a restrictive and ineffective approach. On the contrary, it is necessary to take the problem in a holistic and systemic way, incorporating elements of a social, geographical, environmental and cultural order in the management strategies (Souza Casadinho, J. 2007) (5).
Pesticides can only kill the larvae or adults that are reached in the applications, but as already mentioned insects can acquire resistance.
In addition, mosquitoes, although they do not disperse over great distances, can reach 800 meters in their flights (Almirón, W, 2006) (6). In this case, the adults that are not reached by pesticides, can be distributed in the environment.
5- do the pesticides used have an impact on people's health?
Yes. Although they are presented as "low impact", "innocuous" "friendly to people", the toxins used can have impacts on the health of the population directly or indirectly reached from contamination of water, food, clothing , etc.
In this case, it should be noted that pesticides are classified according to their specific toxicity - potential to cause harm - in five categories, from extremely dangerous to products that "offer practically no danger". Very few times in its categorization, the social and environmental conditions of application are taken into account, which can make a class IV product (which normally does not offer danger) very dangerous (Souza Casadinho, j. 2005) (7).
It should be noted that sometimes the fumigations are carried out without notifying the affected communities, which means that they are exposed to the toxic particles (8). In addition to contaminating water sources, ponds, cisterns, etc.
The damage to health from the toxins used in the campaigns against dengue, in general pesticides that have a pyrethroid chemical classification, can manifest rapidly, with acute symptoms, or otherwise manifest long after the contact has occurred, chronic symptoms.
Among the acute symptoms are; tingling in the eyelids and lips, irritation in the eyes and mucous membranes, sneezing, vomiting, chills. Chronic symptoms include skin blisters, lung inflammation, hormonal disruption. (9, 10, 11)
6- Is there a correct or safe application?
No. Although, as in the application of any technology, risk can be reduced during application, there are so many variables that must be taken into account that safe use is highly unlikely to be put into practice. In pesticides, there is the case of research on effectiveness, safety of use and approval in ideal situations - the laboratory - to later be applied in real situations, in which economic conditions - market pressure -, climatic conditions, access to information often influence the actual conditions of use.
Pesticides are applied without adequate knowledge of their danger, in a rush, with people performing tasks in the vicinity. The sale of fractioned products, the scant information on the labels, the lack of protective equipment, the lack of effective training for those who apply them, are clearly the best evidence that the recommended conditions of use are not implemented. practice.
7- Is it convenient to fumigate the interior of homes?
It is a very dangerous control technique since pesticides can reach water sources, clothes, food, cupboards, tables, chairs, etc., with which they can indirectly reach the people who inhabit them. In this case, the pesticide particles can remain attached for a period of time to various household items, causing health problems for those who ingest, touch or use the contaminated items.
In addition, as higher application rates than those recommended are generally used, the danger in their use increases (Souza Casadinho, Javier, 2005) (12).
8- What can be the strategy to prevent dengue?
It is obvious that the conditions of housing, sanitary infrastructure and environmental sanitation are important factors in the conditions of life and reproduction.
Ing. Javier Souza Casadinho
Pesticide Action Network and its alternatives in Latin America RAPAL
Pesticide Action Network PAN
Professor at the Faculty of Agronomy of the University of Buenos Aires FAUBA
(1) When a disease or health-related event exceeds or exceeds the usual frequency in a specific population, in a place and in a given period of time, it is called an epidemic or outbreak. Zulma Ortiz, and others. - Module No. 6 of basic epidemiology and health surveillance. 2005. Ministry of Health of the Nation. Bs As, Argentina
(2) Almiron, Walter and Rossi, Gustavo. Arthropods of medical interest in Argentina. Chapter 11 Mosquitoes. Mundo Sano Foundation. Bs. As. Argentina.
(3) Ronco A. and others. 2008. Integrated approach for the assessment of biotech soybean pesticide impact on low order stream ecosystems of the Pampasic region. In ecosystem Ecology Research Trends. Pp 209,239 Nova Science Publisherc. Inc.
(4) Agostini and others. (2005) Effect of pesticide application on anuran larvae using field experiments. III Congress of Limnology. Cal III. Chascomús. Argentine Society of Limnology.
(5) Souza Casadinho, Javier. 2007. Persistent Organic Pollutants. Chlorinated pesticides and their alternatives. CETAAR- Secretary of environment and sustainable development. Buenos Aires. Argentina.
(6) Almirón, Walter and Rossi, Gustavo. Healthy world foundation. Argentina.
(7) Souza Casadinho, Javier. Pesticides and children. CETAAR editions. Marcos Paz. Argentina
(8) As happened in Quimilí, Santiago del Estero, on April 1, 2009.
(9) RAPAL. Link Magazine nº 44- April 1999. Lima. Peru.
(10) Peasant and indigenous women. For decent work and a pesticide-free world. 2006. RAPAL. Santiago de Chile.
(11) Endocrine disrupting pesticides. Link Magazine Nº 73. Santiago de Chile. Chile.
(12) Souza Casadinho, Javier. Marcos Paz. Argentina