RIO GRANDE DO SUL, Brazil — Doctors’ groups from Brazil and Argentina warn that it may be a larvicide used to kill mosquitos — not the Zika virus — that’s behind a sudden spike in cases of microcephaly in Brazilian newborns.
Most medical authorities, including those from the Brazilian government and the World Health Organization, suspect that Zika is causing a sharp increase in microcephaly, an extremely rare birth defect that causes reduced brain development and lifelong developmental difficulties.
The ties between the virus and microcephaly are considered strong but largely circumstantial. Outside of Brazil and French Polynesia, none of the pregnant women infected with the virus have produced microcephalic infants. And while Colombia had identified 2,100 diagnosed cases of Zika in pregnant women as of Feb. 1, there have been no reported cases of microcephaly.
Some experts have warned that it may be too soon to tell, as microcephaly often manifests late in a pregnancy.
Meanwhile, others are moving to blame a larvicide introduced into the drinking water in 2014 for the rise in occurrences of the birth defect. In a report issued on Feb. 3 by an Argentinian physicians group called Physicians in the Crop-Sprayed Towns, the doctors noted that most of the microcephaly cases occurred in the Brazilian states where the chemical Pyriproxyfen, the active ingredient in a product called SumiLarv, had been introduced into the drinking water in an effort to combat mosquito populations. A Feb. 2 warning from Abrasco, a Brazilian doctors group, also suggested a possible link.
SumiLarv, which is manufactured by the Japanese corporation Sumitomo Chemical, causes deformations in mosquito larvae that grow in pools of stagnant water, killing them before they can reach adulthood. Initial media reports on the possible link between Zika and SumiLarv reported that Sumitomo is a subsidiary of Monsanto, but the agribusiness giant has distanced itself from the firm and its products in a note published to its blog:
“Monsanto does not manufacture or sell Pyriproxyfen.
Monsanto does not own Sumitomo Chemical Company. However, Sumitomo Chemical Company is one of our business partners in the area of crop protection.”
Officials in Rio Grande do Sul, Brazil’s southernmost state, suspended use of SumiLarv after hearing of the possible link, according to a Feb. 14 report from Fox News Latino:
“On Sunday, Rio Grande do Sul Health Secretary Joao Gabbardo said that, despite the fact that a relationship between the larvicide and microcephaly has not been proven, the ‘suspicion’ that there may be a linkage had led the organizations to decide to ‘suspend’ the use of the chemical.”
Argentine & Brazilian doctors name larvicide as potential cause of microcephaly https://t.co/ERijj3BcAZ #zika #gmo pic.twitter.com/x8BYDxOqZl
— GMWatch (@GMWatch) February 10, 2016
Brazil’s health minister, Marcelo Castro, criticized the reports and the decision to halt use of the chemical:
“That is a rumor lacking logic and sense. It has no basis. (The larvicide) is approved by (the National Sanitary Monitoring Agency) and is used worldwide. Pyriproxyfen is recognized by all regulatory agencies in the whole world.”
But Gabbardo defended his decision, saying, “We cannot run that risk.”
Read the full report released by Argentinian physicians group, Physicians in the Crop-Sprayed Towns: