Dan Wilson
Senior Member.
Zika virus has quickly gained the attention of the world in the past few weeks due to its association with a large outbreak of microcephaly cases in Brazil. However, not everyone thinks the microcephaly outbreak is simply due to Zika virus. Everything from vaccines to GM mosquitoes to man-made pathogens has been accused as the real cause of Brazil's microcephaly.
A new story, however, is gaining a lot of traction on social media and various news sources. A group of doctors from Argentina are proposing that a larvicide, pyriproxifen, is responsible for the outbreak.
Furthermore, they claim that the focus on Zika virus is an intentional cover-up and that a Japanese branch of Monsanto, Sumitomo Chemical, manufactures it (EDIT: Sumitomo is not owned by Monsanto). The report that started this whole story was written by Dr. Medardo Vasquez.
http://www.reduas.com.ar/wp-content/uploads/downloads/2016/02/Informe-Zika-de-Reduas_TRAD.pdf
What is pyriproxifen and is it toxic to humans?
Pyriproxifen is a larvicide (kills insect larvae) that most people have probably used before. In the U.S., it is marketed as Nylar, an anti-flea product used generally by pet owners. It has been marketed since 1996 and has been subjected to a variety of toxicology tests.
Pyriproxyfen is listed as a Group E carcinogen, as in there was no evidence of carcinogenicity found associated with the compound. In this case, however, we are talking about substances that can cause birth defects (teratogens), which are not necessarily in the same category of carcinogens.
Dr. Vasquez claims that because the larvicide interferes with the normal development of mosquitoes, we should not assume it does not affect human development, as many developmental pathways are conserved between humans and distantly related organisms.
He is right that we should not assume that something that affects insects doesn't affect humans. The problem is that he gives no evidence that pyriproxifen is a teratogen. In fact, all of the available toxicological data would suggest that it is not.
https://pubchem.ncbi.nlm.nih.gov/compound/Pyriproxyfen#section=Spillage-Disposal
What's causing the microcephaly outbreak?
The evidence implicating pyriproxifen in the microcephaly outbreak that Dr. Vasquex reports is purely coincidental and also vague. So far the only evidence seems to be that pyriproxyfen (brand name Sumilarv) has started being used within the past 18 months in Brazil in an attempt to control mosquito populations.
No specific regions that received this spraying were mentioned and I have not yet been able to locate any corroborating information on this. That's really all Dr. Vasquez has to offer in his report, there is not much to the link between pyriproxyfen and microcephaly. He seems to be more against the general spraying of chemicals in Brazil altogether, but that is another topic.
The evidence that Zika is causing the outbreak could be described as preliminary. It certainly is a mystery why Zika would suddenly be causing microcephaly when it has a long history of being benign infections. There could very well be another factor involved here, but keep in mind that travel, climate change, and viral mutations could be factors in explaining Zika's sudden spread and emergence of symptoms.
http://www.sciencemag.org/news/2016/01/zika-virus-your-questions-answered
There is currently no evidence that supports the idea that pyriproxyfen is responsible for Brazil's recent reported birth defects. When new outbreaks and public health problems appear, it is important to not let fear-mongering influence decision-making and not be swayed by an explanation that is better described as a guess. More information on this topic will help to clear up the situation, but until then it's better to not simply default to blaming corporations and chemicals.
A new story, however, is gaining a lot of traction on social media and various news sources. A group of doctors from Argentina are proposing that a larvicide, pyriproxifen, is responsible for the outbreak.
Furthermore, they claim that the focus on Zika virus is an intentional cover-up and that a Japanese branch of Monsanto, Sumitomo Chemical, manufactures it (EDIT: Sumitomo is not owned by Monsanto). The report that started this whole story was written by Dr. Medardo Vasquez.
http://www.reduas.com.ar/wp-content/uploads/downloads/2016/02/Informe-Zika-de-Reduas_TRAD.pdf
So what's going on? Is there a cover-up? What's actually causing the microcephaly outbreak? To start off, let's talk about what pyriproxifen is.Malformations detected in thousands of children from pregnant women living in areas where the Brazilian state added pyriproxyfen to drinking water is not a coincidence, even though the Ministry of Health places a direct blame on Zika virus for this damage, while trying to ignore its responsibility and ruling out the hypothesis of direct and cumulative chemical damage caused by years of endocrine and immunological disruption of the affected population.
What is pyriproxifen and is it toxic to humans?
Pyriproxifen is a larvicide (kills insect larvae) that most people have probably used before. In the U.S., it is marketed as Nylar, an anti-flea product used generally by pet owners. It has been marketed since 1996 and has been subjected to a variety of toxicology tests.
Pyriproxyfen is listed as a Group E carcinogen, as in there was no evidence of carcinogenicity found associated with the compound. In this case, however, we are talking about substances that can cause birth defects (teratogens), which are not necessarily in the same category of carcinogens.
Dr. Vasquez claims that because the larvicide interferes with the normal development of mosquitoes, we should not assume it does not affect human development, as many developmental pathways are conserved between humans and distantly related organisms.
He is right that we should not assume that something that affects insects doesn't affect humans. The problem is that he gives no evidence that pyriproxifen is a teratogen. In fact, all of the available toxicological data would suggest that it is not.
https://pubchem.ncbi.nlm.nih.gov/compound/Pyriproxyfen#section=Spillage-Disposal
Developmental or Reproductive Toxicity/ In a 2-generation reproduction study in rats, the systemic NOAEL was 1,000 ppm (87 mg/kg/day). The LOAEL for systemic toxicity was 5,000 ppm (453 mg/kg/day). Effects were based on decreased body weight, weight gain and food consumption in both sexes and both generations, and increased liver weights in both sexes associated with liver and kidney histopathology in males. The reproductive NOAEL was 5,000 ppm. A reproductive LOAEL was not established.
Although you certainly should not regularly consume pesticides, this one has been determined to not be of significant worry so far. But then again, neither has Zika. Zika virus, as Dr. Vasquez points out, has been around for a long time and has never before been linked to any serious health effects even in the event of large outbreaks. So what is the evidence that Zika or pyriproxifen is responsible for the outbreak?Developmental or Reproductive Toxicity/ In /a/ developmental study in rabbits, the maternal NOAEL/LOAEL for maternal toxicity were 100 and 300 mg/kg/day based on premature delivery/abortions, soft stools, emaciation, decreased activity and bradypnea. The developmental NOAEL was determined to be 300 mg/kg/day and developmental LOAEL was /not/ ... determined; no dose related anomalies occurred in the four remaining litters studied at 1,000 mg/kg/day.
What's causing the microcephaly outbreak?
The evidence implicating pyriproxifen in the microcephaly outbreak that Dr. Vasquex reports is purely coincidental and also vague. So far the only evidence seems to be that pyriproxyfen (brand name Sumilarv) has started being used within the past 18 months in Brazil in an attempt to control mosquito populations.
No specific regions that received this spraying were mentioned and I have not yet been able to locate any corroborating information on this. That's really all Dr. Vasquez has to offer in his report, there is not much to the link between pyriproxyfen and microcephaly. He seems to be more against the general spraying of chemicals in Brazil altogether, but that is another topic.
The evidence that Zika is causing the outbreak could be described as preliminary. It certainly is a mystery why Zika would suddenly be causing microcephaly when it has a long history of being benign infections. There could very well be another factor involved here, but keep in mind that travel, climate change, and viral mutations could be factors in explaining Zika's sudden spread and emergence of symptoms.
http://www.sciencemag.org/news/2016/01/zika-virus-your-questions-answered
The take home message here is that there is a lot we still don't know about the microcephaly outbreak and Zika virus itself. Implicating pyriproxyfen as the culprit is an extremely premature assumption that has the attraction of blaming Monsanto for more things.Why has it exploded so suddenly?
There may have been big outbreaks in Africa and Asia in the past that went undetected; scientists weren't paying much attention. But the current massive epidemic was an event waiting to happen. Latin America has huge numbers of A. aegypti, also known as the yellow fever mosquito, an important vector for Zika. (The Asian tiger mosquito, A. albopictus, which is on the rise around the world, is believed to be a vector as well.) In addition, nobody in the Americas had immunity to the virus. Travel makes it worse. Aedes mosquitoes don't fly more than a few hundred meters during their lives; Zika travels from city to city and country to country when infected people get on cars, buses, trains, and planes.
These combined factors meant that the virus had the ability to spread far and fast once it had arrived.
...
Do we know for sure that Zika is causing a rise in birth defects?
No. There is strong circumstantial evidence that areas in Brazil hit hard by Zika have experienced a sharp increase in the number of babies born with microcephaly, a condition in which the head is much smaller than normal because the brain fails to develop properly. But it will take at least several months before the results from the first case-control studies of pregnant women infected with Zika are available. Doctors in Brazil first noticed an increase in cases of microcephaly during ultrasounds of pregnant women in June and July, a few months after the sudden rise in Zika infections. Fetal medicine expert Manoel Sarno, who works at the Federal University of Bahia, says the pattern of brain damage he is seeing now looks distinct from microcephaly caused by other infections, such as cytomegalovirus (CMV) or rubella. He and his colleagues started a study in August that is following women infected with Zika during their pregnancy; the results could come out late summer. Similar studies are underway elsewhere in Brazil and in Colombia.
There is currently no evidence that supports the idea that pyriproxyfen is responsible for Brazil's recent reported birth defects. When new outbreaks and public health problems appear, it is important to not let fear-mongering influence decision-making and not be swayed by an explanation that is better described as a guess. More information on this topic will help to clear up the situation, but until then it's better to not simply default to blaming corporations and chemicals.
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