Since the alarming incidences of the Zika virus in North and South America in 2015, efforts to study the formidable infectious agent and find ways to prevent its spread have intensified. Researchers at the University of Michigan conducted a study to investigate the link between exposure to pesticides like naled and chlorpyrifos — which are used to kill mosquitoes that could potentially be carrying the virus — and child neurodevelopment.

The virus, which is transmitted to humans via a mosquito vector Aedes aegypti, has been linked to serious neonatal malformations as well as Guillain-Barré syndrome — an autoimmune disease which leads to nerve damage and weakness in adults.

John Meeker, an Environmental Health Sciences professor in the School of Public Health, oversaw the project that built on earlier studies done by Betsy Lozoff, Center for Human Growth and Development professor, and her research team.

“There has been a lack of human research on naled, whereas chlorpyrifos has been more well-studied but not for these effects specifically,” Meeker said.

The statistically significant results of the University study showed there were issues with motor skill development in infants that were prenatally exposed to the aforementioned insecticide chemicals.  

According to Monica Silver, a research fellow at the School of Public Health, naled exposure is associated with fine motor function deficits, notably visual-motor coordination, while those exposed to chlorpyrifos exhibited deficits in both gross and fine motor functions. Silver acknowledged the delicate balance between stopping the spread of the virus and avoiding the adverse effects of such preventive measures.

“Zika is a very serious public health threat, but this study highlights that the way we go about combating Zika and other vector-borne diseases needs to be carefully thought out in order to minimize unintended consequences,” Silver said. “One of the aims of my research was to examine the effects of prenatal organophosphate insecticide exposure on infant motor function.”

Currently, the U.S. Environmental Protection Agency regulates the use of both insecticide chemicals. Chlorpyrifos is the most common way to control agricultural pests. However, the United States no longer licenses the chemical due to its propensity for causing neurotoxic damage.

The study was innovative in its incorporation of the potential ecological effect to Lozoff’s study of iron deficiency and neurodevelopment.

“This is an example where we leveraged NIH funding by building an environmental exposure study on top of a nutrition study,” Lozoff said.

Future directions shared among the researchers include a shift toward studies that examine different ways to control the spread of Zika while simultaneously taking into account the unintentional costs of doing so.

“Holistic approaches addressing the full spectrum of the issue to reduce Zika-carrying mosquito populations, mosquito-human interactions, and mosquito bites should be considered in order to minimize both the spread of the virus and the amount of potentially harmful chemicals used,” Meeker said.

Investigators hope that their research exposing the detrimental effects of the chemicals on neonatal health will encourage future studies to focus on the impact of such pesticide usage on the environment and human health.

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