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Oxitec did not release enough mosquitoes to protect Piracicaba

By Fernando Tadeu Moraes From Folha de S.Paulo

Company produces genetically modified insects to combat Aedes aegypti

Biotechnology company Oxitec, which markets GM mosquitoes to combat diseases transmitted by Aedes aegypti , has released less than half of the number of insects considered adequate for Piracicaba (SP) to be protected after the end of the releases, due to occur in May 2018 .

The agreement was signed in May 2016 to treat 11 neighborhoods in the central region of the interior city of São Paulo and provides two years of mosquito release and two years of monitoring of the area. The company of British origin uses genetically modified mosquitos, baptized of “Aedes do well”.

Transgenic insects – all male – have a gene that causes their offspring to die before reaching adulthood. Thus, in copulating with wild females, they render the offspring unfeasible.

For the effect of the intervention to be long-lasting, however, the technique must be applied correctly. Oxitec recommends to the municipalities with which it comes in contact not to carry out projects of less than two years.

The justification is technical. Within the development cycle of Aedes aegypti, consisting of egg, larva, pupa and adult, the largest number of individuals is always in the egg stage.

It is the most complicated combat phase, called the suppression step, since eggs can remain viable for about a year after being deposited. During this one-year period, it is critical that releases of transgenic mosquitoes into the environment occur consistently and in adequate quantities.

Documents provided by the Piracicaba Prefecture show that, from May 2017 – when the phase of suppression should have begun in October of the same year, Oxitec released weekly in Piracicaba less than half – in a few weeks less than a fifth – of the number of mosquitoes considered appropriate for the area to be delivered, after the end of the contract, with a significant impact on the egg bank.

Thus, after discontinuation of releases, reinfestation of the treated area can occur in very short time. The effect, therefore, would not be very different from the combat conducted with more rudimentary techniques, such as the use of insecticides, which eliminates only one phase of the mosquito, leaving others, such as the egg bank, still present in the area.

In another document also provided by the city of Piracicaba, dated January 11, 2018, Oxitec states that six districts of the central region (Cidade Alta, Cidade Jardim, Clube de Campo, Nova Piracicaba, São Dimas and Vila Rezende) more than half the population of the treated area – are still “in the initial phase of suppression”, precisely the stage that should have started in May 2017.

Therefore, by the end of the contract in May 2020, these areas will not be adequately protected, as the contract provides that releases of modified insects should occur by May 2018.


In the 11 neighborhoods of the central region of Piracicaba, where about 60,000 people live, the company released weekly from May to October (see infographic above), a number of modified mosquitoes ranging from 1.5 million to just under 6 million . Proportionally, the number of loose insects ranged from 25 per inhabitant to just under 100 per inhabitant.

According to Folha , however, the technical guidelines recommend a weekly release of 200 mosquitoes per inhabitant, that is, 12 million insects should have been released per week, an index obtained only after October.

The area of the Cecap / Eldorado neighborhood, treated before the central region and following the company’s technical recommendations, provides a good example of comparison.

In the phase of suppression of the area – where 5,000 people live -, which lasted from about May 2015 to May 2016, the release lasted nearly 800 thousand mosquitoes (or about 160 per inhabitant). peaks in the summer of 1.5 million insects (300 per person).

Previous projects of the company present similar numbers. The weekly releases in the Cayman Islands in 2010, for example, ranged from about 200 to 800 insects per inhabitant. In Pedra Branca (BA) in 2011, this rate ranged from just over 200 to 400 mosquitoes / person.

USP researcher Margareth Capurro, a specialist in transgenic mosquitoes, analyzed the rate of insect release in Piracicaba at Folha’s request. According to her, the levels shown by the company will probably cause the work done in the city to be lost in a short time after the end of the contract.

The value of the contract between Oxitec and the city of Piracicaba was R $ 3.7 million. Recently, the company signed agreements with the prefectures of Juiz de Fora (MG) and Indaiatuba (SP).

Capurro, who for some years coordinated with Oxitec the releases of transgenic mosquitoes in Jacobina and Juazeiro, Bahia, but defends the technology used by the company.

“It works and can be applied to the integrated treatment protocol, which also includes measures of basic sanitation, manual withdrawal of breeding grounds and use of larvicides, for example.”


In a statement, Oxitec stated that it “complies with its contracts on a regular and rigorous basis, which includes keeping the city hall informed”.

Asked if he was aware that the releases of modified mosquitoes were below recommended by the company’s technical area, Piracicaba Health Secretary Pedro Mello told Folha that the city’s mayor had never been notified of the fact.

According to the biotechnology company, “the vector suppression project developed by Oxitec does not foresee release of fixed amount of transgenic mosquitoes”.

According to the company, the smallest release of insects occurred as a result of the period of the year – mostly winter – in which “low rainfall and low temperatures (typical of the season) were observed, and, consequently, low infestation of wild mosquito “.

“During the seasonal period when the population of wild mosquitoes is smaller, the number of genetically modified mosquitoes released by Oxitec was also lower. Wild mosquito populations were monitored at all times by the use of ovitraps in the neighborhoods,” said Oxitec.

According to Folha , however, the low releases are a consequence of industrial problems in the production of the modified insects occurred in the factory built by the company in Piracicaba.

According to the company, “the Oxitec project in Piracicaba was the first in an operational scale that adopted this strategy of seasonal adaptation in the number of mosquitoes.”

In the case of the Cecap / Eldorado neighborhood, the first dealt with by the company in Piracicaba (as of May 2015), the issue of seasonality did not carry the same weight.

There, the weekly releases during the winter suppression phase were at the level of 160 transgenic mosquitoes per capita.

IMAGE: Mosquitoes on a screen. Creation of transgenic Aedes Aegypti mosquitoes at the Oxitec company in Campinas. – Lalo de Almeida / Folhapress

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