I am a medical doctor and professor of public health, and I am also the father of a beautiful daughter and uncle to the world’s best niece.  We also live in Rio de Janeiro, Brazil.  We are being inundated with information and misinformation about Zika and its correlation to microcephaly.  There is a lot of fear, which is the perfect environment for people to spread false information.

When I saw friends sharing an article based on fear and not facts, I knew I had to comment due to my background.  If you have not seen this article, you can read it here, but it claims the reported increase in microcephaly in Brazil is caused not by Zika or any other virus, but a larvicide called Pyriproxyfen.  Larvicides are used to kill mosquito larvae and since Zika is spread by mosquitoes this bit of misinformation could cost lives.

The article references a mysterious document purportedly written by “Argentine doctors.” The organization that undersigns it is the “Red Universitária de Ambiente Y Salud”, which is a loose affiliation of individuals dedicated to fighting the use of pesticides, agrotoxics and the like. Perhaps the biggest clue that the information in the document is not trustworthy is that the name of larvicide called into question is repeatedly spelled wrong throughout.

I will address the claims made in the executive summary of the document point by point.I’ve copied directly from the document, including the misspellings.

“1-Dengue epidemic in Brazil persists endemically (on an ongoing basis) due to the marginalisation and misery of millions of people, especially in Northeast Brazil. On top of that, Zika virus, a similar disease although more benign, is now spreading.”

This is correct to some extent. Dengue persists for a number of factors, attributing it exclusively to the “marginalization and misery of millions of people, especially in NE Brazil” is quite reductionist.

“2. A dramatic increase of congenital malformations, especially microcephaly in newborns, was detected and quickly linked to the Zika virus by the Brazilian Ministry of Health. However, they fail to recognise that in the area where most sick persons live, a chemical larvicide producing malformations in mosquitoes has been applied for 18 months, and that this poison (pyroproxyfen) is applied by the State on drinking water used by the affected population.”

There are three factual errors in the above statement: (1) the increase in cases of microcephaly were detected in October 2015, which means they resulted from pregnancies initiated at most by January of that year (dating back 40 weeks). The larvicide was already in use at almost two years before that.  If the larvicide was the cause of the reported increase in cases of microcephaly we would expect to see the increase much earlier. (2) This specific larvicide is used all over Brazil, not just in one region, so if the larvicide was the cause we would expect to see the increase all over Brazil, but we aren’t seeing that, the cases are concentrated in the Northeastern states? The larvicide was also never used in Recife, the capital of the most affected state, Pernambuco, and the city with most cases. (3) The larvicide does not produce “malformations” in mosquitoes, but disrupts endocrine regulation in a way that keeps the larvae from maturing. Big difference.

“3. Previous Zika epidemics did not cause birth defects in newborns, despite infecting 75% of the population in those countries. Also, in other countries such as Colombia there are no records of microcephaly; however, there are plenty of Zika cases.”

This is incorrect: Cases of microcephaly were retrospectively detected in Polynesia.  Additionally pyriproxyfen has been used in Colombia since 2010 so if pyriproxyfen was the cause we’d expect to see the same increase there in 2010 and 2011, but that hasn’t happened.

“3. The pyroproxyfen being used (as recommended by WHO) is manufactured by Sumimoto Chemical, a Japanese subsidiary of Monsanto.” [And yes, the original document has two #3 entries.]

I could not confirm the information that Sumitomo is a “subsidiary” of Monsanto, although it seems to have several partnerships with it. I’m not sure how the alleged association with Monsanto is supposed to support the document’s claims that the larvicide and not Zika is responsible for the increase in cases of microcephaly.

“4. Brazilian doctors (Abrasco) are claiming that the strategy of chemical control is contaminating the environment as well as people, that it is not decreasing the amount of mosquitoes, and that this strategy is in fact a commercial manoeuvre from the chemical poisons industry, deeply integrated into Latin American ministries of health as well as WHO and PAHO.”

Abrasco’s technical note does make that claim, but it does not claim that pesticides, larvicides or any another chemical product is responsible for the occurrence of microcephaly.  In fact Abrasco has stated just the opposite to what the document claims, that they do not believe there is a link.

“5. Massive spreading using planes, as the governments of Mercosur are considering, is criminal, useless, and a political manoeuvre to simulate that actions are taken. The basis of the progress of the disease lies in inequality and poverty, and the best defence are community-based actions.”

I assume that by “massive spreading using planes” refers to the aerial spraying of the larvicide. If the larvicide was to be sprayed aerially, this would not be a criminal act as the government has the authority to do so.  The group may disagree with that tactic, but it is not a criminal offense.

“6. The last strategy deployed in Brazil, and which might be replicated in all our countries, is the use of GM mosquitoes —a total failure, except for the company supplying mosquitoes.”

There is no reference in Abrasco’s technical note to the efficiency of the use of transgenic (sometimes referred to as genetically modified (GM))mosquitoes. There are controversies about its use, but to claim to be a “total failure”, especially when there are published studies indicating the exact opposite, is an undue exaggeration.

Most importantly, what was left out of this discussion: the evidence in the studied cases of microcephaly of brain injury caused by infection, which does not fit this narrative.

If there was reasonable evidence of an association between the larvicide and microcephaly I would want it banned from use to protect my my daughter and niece, but there isn’t reasonable evidence of the proposed association of the larvicide with microcephaly.  It seems the organization behind the conspiracy document I noted above has a political agenda, which could be commendable if it was based on science, but that is interfering improperly with its assessment of the problem.

Let me be clear, this does not mean there is no risk in the use of that larvicide, or even that some of the policies directed at mosquito population reduction in the last 30 years have indeed been shown to be ineffective and potentially harmful. Nor does it mean that Zika has been firmly established as the cause of the microcephaly outbreak, but the pyriproxyfen theory lacks evidence. The Zika hypothesis has the most evidence to support it at present, but that may change.

If you have questions about mosquito borne tropical diseases like Zika, dengue or chikungunya a good place to start is the journal Epidemiology and Health Services.  They’ve created a page that provides plain-language information in English, Portuguese (the national language of Brazil) and links to reputable sources about the outbreak.

Finally I would ask you to reconsider sharing bad information, like the conspiracy theory I fact-checked above, via email and social media.  While it may seem harmless, the microcephaly outbreak is a true public health crisis and misinformation can cause people to disregard evidence-based recommendations that could save the lives or the lives of their babies.

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Categories: Ages + Stages, Chronic Illnesses + Conditions, Disability + Disability Advocacy, Infectious Disease + Vaccines, Newborns + Infants, Science 101 + Mythbusting