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Nothing brings out a good conspiracy theory quite like an emerging disease, and Zika is no exception. Often these ideas and their perpetuation are harmless; however, a newer theory focused on Zika falls more in the reckless and dangerous category. The story goes that the observed spike in infants born with microcephaly actually has nothing to do with Zika and is due to spraying with the insecticide pyriproxyfen. Because Zika is primarily spread by mosquitoes, its emergence in the Western Hemisphere has been largely addressed by mosquito control measures, and so the theorists allege, this is actually what is causing the problem (neatly disregarding that the spraying began in 2014, while the microcephaly cases spiked in late 2015). This article from The Ecologist states that the link between Zika and microcephaly is “looking increasingly tenuous”, and that Brazilian and Argentine physicians doubt that the link exists. The continued insistence that there is a link between the virus and the birth defect is only to encourage mosquito spraying, thus making money for the parent company of pyriproxyfen’s manufacturer…Monsanto!
It’s a nice story, no? It explains everything, eschews poisons, and blames Monsanto-truly the conspiracy theory trifecta. This story has been shared on virtually every form of social media, and has spawned numerous blog posts with titles like “BANG: Not Zika. Brazilian/Argentine Doctors Say: Pesticides” and “Microcephaly: Is it the Zika 'Virus' or pesticides & birth defects?” Needless to say, the claims within these posts are even less grounded in reality.
Here are the known realities. The link between Zika and microcephaly is not “growing increasingly tenuous”; in fact, it is inarguably getting stronger. Local hospitals are reporting that microcephaly case volumes are starting to go down, presumably due to increased mosquito control efforts. If additional pesticide spraying was the cause case volume would go up even faster, would it not? If one asks the question “what is causing the microcephaly spike in South America” and the two possible answers are “Zika virus” or “Pesticides”, I see two lines of thought:
1.) Increased pesticide spraying (leads to) fewer mosquitoes (leads to) fewer mosquito bites of pregnant women (leads to) lower Zika rates (leads to) lower microcephaly rates.
2.) Increased pesticide spraying (leads to) more pesticide-exposed pregnant women (leads to) higher microcephaly rates.
Which pattern fits the data?
That is just patterning though. To move beyond speculation, one would have to find Zika virus in the women or the babies. As it turns out, that has been done by multiple scientists, at multiple institutions, using multiple methods. Some good evidence came from the detection of Zika virus in the amniotic fluid of infected pregnant women, meaning that this virus is capable of crossing the placenta and infecting fetuses. Even better evidence came from reports of scarring and Zika virus particles in the eyes of microcephaletic infants. The best evidence though? Examination of stillborn babies, spontaneously aborted (i.e., miscarried) fetuses, and a terminated pregnancy all had living, replicating Zika virus in the brain.
Why would Argentine doctors say that it was pesticides, then? Shouldn’t they know? Well… not all Argentine doctors said that. Not a majority of Argentine doctors said that. A small group of Argentine doctors claimed that, all of whom belong to an organization called Physicians in the Crop-Sprayed Towns. With respect to the health consequences related to extensive crop spraying, I politely suggest that perhaps these particular Argentine doctors are looking through a decidedly biased lens. Why are the cases mostly in Brazil? Because Brazil has the highest population, the most infected patients, and the best reporting system to ensure that they are counted. Why are people saying that the microcephaly cases spiked before Zika arrived? This relates the somewhat nebulous guidelines for diagnosing microcephaly and a retrospective report reevaluating older charts of infants with congenital heart defects. Does it mean that the spike in microcephaly is not real? Absolutely not.
Who cares though? People are entitled to their opinions. Isn’t this harmless? No. No, it isn’t harmless at all. Mosquito control saves lives- period- and not just because of Zika virus. It cuts down rates of dengue fever, dengue hemorrhagic fever, yellow fever, chikungunya, and malaria. All of those diseases can kill healthy children and adults. If mosquito control measures are cut back, rates of all 6 diseases as well as many others will increase. The author of this theory is acting rashly and irresponsibly. Please don’t be part of the process!