Dengue and Monocultures. Some points to reflect on

To a greater or lesser extent, the media has echoed the dengue epidemic (1) that devastates our country. Now, beyond listing the cases by province and the consequences on health, the practices of eliminating domestic water sources and the advance of fumigation, little is delved into the causes of this phenomenon and, more importantly, the consequences. that massive fumigations can have on the health of communities affected by dengue and by said spraying, most of the time carried out in a careless manner, that is without taking into account the environment where they are carried out.

Housing conditions, sanitary infrastructure and environmental sanitation constitute important factors in the living and reproductive conditions of insects and therefore must be taken into account in management strategies. Regarding social factors, the characteristics of the population, their habits, customs and levels of organization must be taken into account. Any measure may be ineffective if a substantial reduction in poverty conditions is not achieved along with a continuous and permanent evaluation of both the process implemented and the monitoring of the disease.

1- What could be the causes of the spread of the disease?

The causes are multiple but related to each other. As is known, the progress of the disease has to do with the expansion of the distribution areas and the possibilities of survival of the Aedes aegypty mosquito, both of which are related to the current agricultural model and climate change, these in turn linked to each other. .

Although it is possible to talk about the multicausality of diseases, there is no doubt that the production model based on the monoculture of transgenic soybeans, the use of herbicides, fungicides and insecticides has its impact on the reproduction rate and survival of the vector.

Firstly, the deforestation and burning of forests and mountains, to dedicate the land to soy cultivation, has determined the migration of mosquitoes to other areas where they have found optimal conditions for their survival. In this case, climate change, especially the rise in temperatures and changes in humidity conditions, also has a notable influence.

Embryonic eggs can resist extreme temperatures, remaining viable between 7 months to a year (Almirón, W, 2006) (2).

Since monocultures are unsustainable in themselves, they require the increasing use of insecticides and herbicides, which 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 the development of the natural enemies of mosquitoes, in this case toads and fish that devour 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, the 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 take two forms:

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 – making 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, normal doses of the pesticide become ineffective. This generates an increase in doses, replacement with more toxic products and even an 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 climate change that manifests itself from an increase in temperature and humidity conditions has 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.

Now, climate change has not occurred naturally or by chance; on the contrary, it is related to both the increase in industrial activities, transportation, the burning of forests that generate carbon dioxide, and the decrease in the area covered by trees. that absorb that compound. Once again we found a relationship between the agricultural production model and the spread of the disease.

4- Is the use of pesticides effective in reducing 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 social, geographical, environmental and cultural order in management strategies (Souza Casadinho, J. 2007)(5).

Pesticides can only kill the larvae or adults that are affected by the applications, but as already mentioned, insects can acquire resistance.

Furthermore, mosquitoes, although they do not disperse long distances, can reach 800 meters in their flights (Almirón, W, 2006)(6). In this case, the adults that are not affected by pesticides can be distributed in the environment.

5- Do the pesticides used have an impact on people's health?

Yeah. Although they are presented as “low impact”, “harmless”, “friendly to people”, the toxins used can have impacts on the health of the population reached directly or indirectly through the 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 rarely do their categorization take into account the social and environmental conditions of application, which can make a class IV product (which normally does not present danger) very dangerous (Souza Casadinho, j. 2005)(7).

It should be noted that sometimes fumigations are carried out without notifying the affected communities, which means 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 campaigns against dengue, generally pesticides that have a pyrethroid chemical classification, can manifest quickly, acute symptoms, or otherwise manifest a long time after contact, 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, and hormonal disruption.(9, 10, 11)

6- Is there a correct or safe application?

No. Although, as in the application of any technology, the risk can be reduced during application, there are so many variables that must be taken into account that safe use is very 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 - and then they are applied in real situations, in which economic conditions - market pressure -, climatic conditions, the access to information often influence the true conditions of use.

Pesticides are applied without adequate knowledge of their danger, in a hurry, with people carrying out tasks in the vicinity. The sale of fractionated products, the limited 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 carried out. practice.

7- Is it advisable to fumigate the interior of homes?

It is a very dangerous control technique since pesticides can reach water sources, clothing, food, cupboards, tables, chairs, etc., which can indirectly reach the people who live there. 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.

Furthermore, since higher application doses than those recommended are generally used, the danger in its use increases (Souza Casadinho, Javier, 2005) (12).

8- What can be the strategy to prevent dengue?

It is obvious that housing conditions, health infrastructure and environmental sanitation constitute important factors in living and reproductive conditions. www.ecoportal.net

Agr. Eng. Ms. Sc. Javier Souza Casadinho
Action Network on pesticides and their alternatives in Latin America RAPAL
Pesticide Action Network PAN
Professor at the Faculty of Agronomy of the University of Buenos Aires FAUBA

Notes:

(1) When a disease or health-related event exceeds or exceeds the usual frequency in a specific population, in a place and in a certain 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. Buenos Aires, Argentina

(2) Almiron, Walter and Rossi, Gustavo. 2005. Arthropods of medical interest in Argentina. 2005. Chapter 11 Mosquitoes. Healthy World Foundation. Bs. As. Argentina.

(3) Ronco A. et al. 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 et al. (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. 2005. Arthropods of medical interest in Argentina. 2005. Chapter 11 Mosquitoes. Healthy World Foundation. Bs. As. Argentina.

(7) Souza Casadinho, Javier. 2005. Pesticides and children. CETAAR editions. Marcos peace. Argentina

(8) As happened in Quimilí, Santiago del Estero, on April 1, 2009.

(9) RAPAL. Enlace Magazine No. 44 - April 1999. Lima. Peru.

(10) Peasant and indigenous women. For decent work and a world free of pesticides.2006. RAPAL. Santiago de Chile.

(11) Endocrine disrupting pesticides. Enlace Magazine No. 73. Santiago de Chile. Chili.

(12) Souza Casadinho, Javier. 2005. Pesticides and children. CETAAR editions. Marcos Paz. Argentina