Right now, the Internet is abuzz with questions over a report that states it’s more likely that the outbreak of microcephaly - a rare neurological disorder that causes newborns to develop abnormally small skulls and brains - is linked to pesticides rather than the spread of Zika virus. The pesticide in question is pyriproxyfen - a larvicide that targets the Zika-spreading Aedes aegypti mosquito, produced by Sumitomo Chemical.
"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 (pyroproxifen) is applied by the State on drinking water used by the affected population," the report, published by Argentinian group Physicians in Crop-Sprayed Towns (PCST) last week, states.
The group adds that it’s "not a coincidence" that cases of microcephaly have proliferated in Brazil where pyriproxyfen is being used, while in Colombia, Zika infections have not been linked to microcephaly, despite the fact that it has the second highest incidence of the virus after Brazil.
And even within Brazil, not every case of microcephaly has been linked to presence of Zika. "After experts scrutinised 732 of the cases, they found that more than half either weren’t microcephaly, or weren’t related to Zika," The Washington Post reported last month.
In response to the report, one Brazilian state has suspended use of pyriproxyfen until further notice.
"We decided to suspend the use of the product in drinking water until we have a position from the Ministry of Health, and so, we reinforce further still the appeal to the population to eliminate any possible mosquito breeding site," Joao Gabbardo dos Reis, state health secretary in Rio Grande do Sul, told the press over the weekend.
While the WHO has explicitly said that the link between the microcephaly and Zika outbreaks has not yet been confirmed, this is less about a lack of scientific evidence and more about giving scientists the time they need to carry out their investigations properly.
If they’re going to explicitly state that there is a link, they want to be 100 percent sure that this is backed by solid, causal evidence showing how an infection by Zika virus can cause biological changes in a foetus that severely disrupts growth.
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