Insecticide or Zika virus?

Environmental chemists are now questioning whether it is the Zika virus that is behind the birth defects in Brazilian children. Researchers at institutions such as Linköping University will be investigating whether the cause could instead be an insecticide against mosquitoes.

MyggaPhoto credit: Wikipedia“The pesticide pyriproxyfen operates at the hormonal level, preventing mosquito larvae from maturing. The thought is that in a similar way, it could arrest brain development in human foetuses. There’s a very small window of time during pregnancy in which it could have an effect,” says Henrik Kylin, professor of Environmental Chemistry at the Department of Thematic Studies – Environmental Change.

The toxin is added to the drinking water tanks that many Brazilian households have on their roofs, and where mosquitoes infected with the virus lay their eggs. Pyriproxyfen has a low acute toxicity, and the method is recommended by WHO, the World Health Organisation.

Professor Kylin has no proof that the toxin hypothesis is more likely than that the Zika virus is the culprit. The problem, according to him, is that people have tied themselves to the Zika hypothesis without having studied other explanatory models.

“They risk stopping the search for other causes. Global brainstorming and research in the field, not just behind a desk, are needed now.”

Professor Kylin will be participating in a major survey of existing studies, organised by Swetox, a network for research of such things as environmental toxins that includes several Swedish universities.

“The only thing we can do now is research as intensely as possible. The insecticide is one of many alternative explanatory models that need to be investigated,” he says.

Other experts have a different interpretation. Toxicologist Bert-Ove Lund, at the Swedish Chemicals Agency, told Radio Sweden that there are no indications of deformities in the animal studies done on pyriproxyfen, despite very high doses being administered.

Åke Hjelm 17 Feb 2016