Brazil, Southern Cone

Brazil Health Official Defends Controversial Decision to Halt Use of Pesticide in Fight Against Zika

February 22, 2016 By Cleuci de Oliveira

The health commissioner of Brazil’s southernmost state defended his ban of a pesticide used to prevent the spread of the Zika virus, telling the Latin America News Dispatch that residents should not be exposed to toxic chemicals in their drinking water.

“We recognize that potable water should not contain mosquito larvae or eggs,” said Health Commissioner João Gabbardo dos Reis, who heads the Rio Grande do Sul State Department of Health. “But it likewise should not be contaminated with poison.”

The commissioner’s Feb. 13 decision came on the heels of a provocative report arguing that the larvicide pyriproxyfen, and not the mosquito, was to blame for a surge in Brazilian newborns with abnormally small heads.

The report, published by an Argentine group that campaigns against pesticides and genetically modified organisms, was disseminated widely throughout Brazilian social media. The heated Internet chatter that ensued, coupled with the decision by Reis, prompted the country’s Ministry of Health to issue an official rebuke.

“Unlike the link between the Zika virus and microcephaly, which has already been confirmed by tests conducted on blood, tissue and amniotic fluid samples, the link between pyriproxyfen and microcephaly has no scientific basis whatsoever,” the statement read.

The fallout to the Argentine report is the latest and most dramatic example of the feverish rumor mill that has emerged as a side-effect to Brazil’s deepening crisis. In the past several weeks, everything from vaccines to genetically engineered bugs have been blamed for the microcephaly epidemic, despite growing international consensus that the culprit is Zika.

But the conspiracy theories go beyond the current disease outbreak. In December, the Brazilian government launched a website aimed exclusively at debunking rumors about itself.

“There have been so many fake stories about the current administration on the Internet,” said Edgard Matsuki, a journalist and founder of, a popular rumor-tracking website. “This has happened precisely because people are unhappy with their leaders. These rumors reinforce their discontent, and as a result get shared more frequently as facts.”

Matsuki credits the explosion of the larvicide rumor to Reis’ decision to suspend its use. “The story had circulated on the Internet before that, but not nearly with the same intensity,” he said.

Since 2014, the Brazilian government has added pyriproxyfen to water tanks in areas where the Aedes aegypti mosquito commonly breeds. The mosquito, which carries not only Zika, but dengue and chikungunya, tends to lay eggs in stagnant water stored inside man-made containers. The chemical works by disrupting the mosquito’s development, preventing it from growing wings or reproductive organs.

Pyriproxyfen is one of 12 larvicides approved for use in drinking water by the World Health Organization. Research conducted by a team of WHO scientists, according to a statement released on Friday, found no evidence that it affects pregnancies or fetal development.

“When people drink water from containers that have been treated with pyriproxyfen, they are exposed to the larvicide — but in tiny amounts that do not harm their health,” the statement read. The dosage recommended for use by the Brazilian Health Ministry is far below the one approved by WHO.

Reis expressed concern about the potential room for error.

“It’s one thing for the manufacturer to say that their product can be used safely at a particular dosage,” he said. “But the product is handled by people in isolated pockets of the state, and they can make mistakes when it comes to measuring.”

Reis has opted for what he called a “mechanical solution” to replace the chemical’s use in Rio Grande do Sul. His department will encourage residents to cover their water tanks, he said, and scrub them down once a week. He defended this plan as a realistic approach to keep mosquitoes from spreading, citing how few water tanks exist in the state.

“The water system in Rio Grande do Sul differs from the one in Brazil’s northeast, where both Zika and microcephaly are prevalent,” he said. “Over 92 percent of households here are connected to our public water supply. So the number of people who store their drinking water in tanks is very low.”

The rumor that pyroproxyfen is behind the birth defects originated with the Argentine coalition Physicians in the Crop-Sprayed Villages, and was based on a misinterpreted statement by the Brazilian Common Health Organization (ABRASCO).

Citing ABRASCO, the Argentine group argued that the use of pyriproxyfen in regions where the number of microcephaly cases spiked “is not a coincidence,” and that the Brazilian government is “trying to ignore its responsibility” by focusing on Zika instead of the chemical.

“ABRASCO opened our eyes,” said Dr. Nicolás Loyacono, the national coordinator for the anti-GMO group. “We are not dealing with this problem in Argentina, so we took the information from them.”

Loyacono said members of his organization will issue a public statement this week, with the aim of discouraging the Argentine government from working with pyriproxyfen.

ABRASCO, in an e-mail, denied ever saying that pesticides were behind the rise of microcephaly cases in Brazil. The association also condemned those who circulated the theory.

“It is well known that moments of uncertainty like the one we are living through generate a sense of insecurity among the public. As such, it provides fertile ground for untruths and unscientific claims to spread,” the e-mail read. “ABRASCO rebukes this kind of behavior, which makes light of the anxiety and suffering felt by those who are most vulnerable. We ask that researchers and the media display caution during this critical time.”

The Argentine report decried to use of pyriproxyfen in the state of Pernambuco, considered the epicenter of the microcephaly epidemic. But officials in the capital Recife, which had the highest number of suspected microcephaly cases in 2015, said they have never used the chemical larvicide, opting instead for a biological alternative.

“We do not use pyriproxyfen,” said Recife’s Executive Secretary for Health Cristiane Penaforte. She said that the city has used BTI, a biological larvicide, since 2002.

“Recife is a city surrounded by water, so we chose the product that would have the least impact on the environment,” Penaforte said. “We have used BTI for fourteen years, and have never had any problems with it.”

Loyacono, for his part, expressed remorse that his group’s report set off a wave of anxiety.

“We could have done better, that’s true. We never wanted to created panic. We wanted to open people’s eyes.”

About Cleuci de Oliveira

Cleuci de Oliveira is a New York City-based journalist from Brasília, Brazil.


[…] community and dismissed by Brazil’s Ministry of Health. LAND’s Cleuci de Oliveira spoke to Rio Grande do Sul Secretary of Health João Gabbardo dos Reis about his controversial decision to halt the use of a pesticide that is instrumental in the fight […]

[…] community and dismissed by Brazil’s Ministry of Health. LAND’s Cleuci de Oliveira spoke to Rio Grande do Sul Secretary of Health João Gabbardo dos Reis about his controversial decision to halt the use of a pesticide that is instrumental in the fight […]

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