Government’s response is scientifically flawed

Recently we broke the story of the Argentine and Brazilian doctors’ and health researchers’ reports linking an increase in cases of the birth defect microcephaly in Brazil with pyriproxyfen, a larvicide sprayed to combat mosquitoes.

Babies with microcephaly are born with an abnormally small head and often have brain damage.

The story quickly went viral, generating a mass of media coverage – for example, articles in Ecowatch and The Ecologist.

The doctors’ and researchers’ reports challenged the popular assumption that the microcephaly cases were caused by the Zika virus, which is carried by mosquitoes. The larvicide pyriproxyfen was being sprayed to kill mosquitoes, but the doctors and researchers believed that the ‘cure’ for the mosquitoes may have been the actual cause of the birth defects.

Predictably, health officials in Brazil have now dismissed any potential link between microcephaly and the larvicide (see article below). This is expected, as they could be liable for any harm caused by this state-sponsored spraying programme.

Notably, the Brazilian federal government’s response is scientifically flawed. It states that “there had been no scientific study that linked pyriproxyfen to microcephaly”. But the inadequacy of industry-sponsored regulatory tests for teratogenic (causing birth defects) effects of pesticides is well known.

And pyriproxyfen does not appear to be well studied by independent scientists.

The Brazilian government also said, “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.”

However, these tests showing the presence of the Zika virus in the blood of newborns and/or mothers affected by microcephaly do not prove a causative link between Zika and microcephaly. This presence could well be coincidental (the person happens to carry the virus but it’s not causally connected to birth defects) or “opportunistic” (taking advantage of a weakened immune system).

The government’s statement that “some localities that do not use pyriproxyfen also had reported cases of microcephaly” proves nothing. Glyphosate herbicides are also linked with microcephaly and are sprayed on GM crops in large areas of the country. And several studies link exposure to other pesticides with anencephaly, a more extreme form of microcephaly in which the foetus does not develop a forebrain.

What is needed before the pyriproxyfen/microcephaly link can be dismissed is epidemiological studies to see if there is an increase in microcephaly in areas where pyriproxyfen has been sprayed, as well as controlled animal studies using realistic doses comparable to those to which humans are exposed.
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Zika virus: Brazil dismisses link between larvicide and microcephaly

By Donna Bowater
The Telegraph, 15 Feb 2016
http://www.telegraph.co.uk/news/worldnews/zika/12157747/Zika-virus-Brazil-dismisses-link-between-larvicide-and-microcephaly.html

* Fears grow over a link between pyriproxyfen and microcephaly but the Brazilian health ministry played any link down

Health officials in Brazil have dismissed claims that a larvicide could be responsible for a rise in cases of microcephaly, and not Zika virus.

A report by Argentinian doctors suggested pyriproxyfen, which is used to control the Aedes aegypti mosquito, could be associated with the deformity, which impairs foetal brain development.

The organisation, Physicians in the Crop-Sprayed Towns, said the substance had been introduced into drinking water supplies since 2014 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, and that this poison (pyroproxifen) is applied by the state on drinking water used by the affected population,” the report said.

In response, the local government in Rio Grande do Sul, a state in the south of Brazil, suspended the use of pyriproxyfen on Saturday.

“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,” said Joao Gabbardo dos Reis, state health secretary in Rio Grande do Sul.

However, the federal government was quick to dismiss the fears in a statement.

It said there had been no scientific study that linked pyriproxyfen to microcephaly, which has been confirmed in 462 babies, with 41 cases linked to the mosquito-borne Zika virus.

“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,” the statement said.

“It’s important to state that some localities that do not use pyriproxyfen also had reported cases of microcephaly.”

The government said it only used larvicides recommended by the World Health Organisation (WHO).

Hawaii declared a state of emergency over Zika on Monday, becoming the first US state to take such action.

David Ige, governor of the islands, said that the proclamation was “a preventative measure” as there have been no cases of the virus being transmitted in the state so far. Four people in Hawaii have caught the virus while abroad, the Center for Disease Control said.

There have, however, been some cases of dengue fever on the island of Hawaii. The statement from the governor's office said such cases "continue to be fewer" and further between, but the battle to break the cycle of transmission continues.

"There have been no locally acquired Zika cases in the US or Hawaii, and we'd like to keep it that way," said Mr Ige. "This is about getting in front of the situation across the state."

Around 50 people in the US are known to have contracted the virus, in 17 states. All of them had travelled to Latin America.

Scientists around the world are currently racing to develop a vaccine for Zika virus, with clinical trials expected within a year to 18 months.