Move over, Zika virus. A group in Argentina is claiming that the microcephaly cases that have broken out across Latin and South America are due to a type of larvicide in the drinking water rather than Zika virus itself. Could pesticides be causing mirocephaly, rather than Zika? According to a team of Argentinian doctors, Physicians in Crop-Sprayed Towns (PCST), the larvicide pyriproxyfen could possibly be linked to the rise in babies born with the fetal brain impairment instead.
In a report, PCST linked the rise in microcephaly to the introduction of pyriproxyfen to the drinking water in affected areas of Brazil. "In the area where most sick persons live, a chemical larvicide producing malformations in mosquitoes has been applied for 18 months," the report said, according to The Telegraph. "This poison (pyroproxifen) is applied by the State on drinking water used by the affected population."
Pyroproxifen, which is distributed by a company associated with Monsanto, is used to control populations of the Aedes aegypti mosquito, which works as a vector for Zika, dengue, and chikungunya (none of which are particularly pleasant viruses to contract). One of the long-standing problems in areas plagued by these diseases is how to control Aedes aegypti, since its females spread the disease. In some countries, such as the Dominican Republic, the government launched a campaign to lower mosquito populations during critical months by encouraging people to add a small amount of chlorine to any standing water supplies. Pyroproxifen is a way to combat the spread from a single source. So far, however, the public seems divided on whether or not pyroproxifen is actually to blame.
In response to PCST's report, a southern Brazilian state, Rio Grande do Sul, suspended use of pyriproxyfen until further research could be carried out by the Ministry of Health. The federal government, however, was quick to shoot down any claims about a correlation between the larvicide and microcephaly.
"It’s important to state that some localities that do not use pyriproxyfen also had reported cases of microcephaly," the federal government said in a statement, according to The Telegraph. "Unlike the relationship between the Zika virus and microcephaly, which has had its confirmation shown in tests that indicated the presence of the virus in samples of blood, tissue and amniotic fluid, the association between the use of pyriproxyfen and microcephaly has no scientific basis."
While I honestly dislike Monsanto as much as the next sane person (they don't exactly inspire warm and fuzzy feelings), science seems to be siding with Brazil's federal government on this one. The World Health Organization (WHO) hasn't confirmed the Zika-microcephaly link yet, but ScienceAlert claims this is only because scientists are still going through the procedures to formally prove the causation, not because of a lack of evidence.
The changes doctors are seeing in babies with microcephaly don't hint at damage caused by a pesticide. According to ScienceAlert, neurologist Vanessa van der Linden told the BBC, "Clinically, the changes we see in the scans of babies suggest that the injuries were caused by congenital infection and not by larvicide, drug, or vaccine."
Additionally, Recife — the Brazilian city with the highest amount of microcephaly cases — does not use pyriproxyfen in its drinking water. Pyriproxyfen, on the other hand, is used largely in the United States and Europe (although not in drinking water) and has undergone safety tests before approval. If the larvicide was causing microcephaly, it's likely we would be seeing rising numbers of mirocephaly more widespread across the globe.
Scientists are still in the early stages of combating the rise in microcephaly, and I can't say I blame doctors for looking for any issues that could be causing the spike in cases (that is good science, after all). However, until causation is proved one way or another — whether the disease is connected to Zika or, more doubtfully, to pyriproxyfen — we need to be steering the conversation towards what will actually help lower cases at the moment: Women in affected areas need access to realistic, liberal family planning, for their own health and that of their children.