The microcephaly epidemic in Brazil has been speculated to be caused by the Zika virus. However, a study published on June 15 in the New England Journal of Medicine claims Zika may not be the real cause of microcephaly after all so further research is still needed to verify this.

In Brazil, more than 1,500 microcephaly cases have been recorded. But the researchers from the New England Complex Systems Institute (NECSI), an independent research and educational institution, say microcephaly cases were not found in other countries hit with Zika virus, as in the case of Colombia.

A recent data analysis reveals that the 12,000 Colombian mothers infected with Zika, all of whom have Zika infection symptoms, did not give birth to microcephalic infants, babies with small head that can lead to learning problems. The four cases of Zika and microcephaly were not included in the analysis since these mothers did not show any symptoms of Zika infection.

zika virus

Child with microcephaly. Credit: Allison Stillwell Young/Flickr

These four cases were the only microcephaly cases related with the Zika infection. Moreover, experts say at least two in 10,000 births are expected to be affected with microcephaly, even in normal pregnancies not troubled by Zika. The four microcephaly cases is just what has been anticipated in Colombia, where there were 20,000 births.

The findings imply that there could be another cause for microcephaly in Brazil. Some researchers say Brazil’s microcephaly cases could be blamed to the pesticide pyriproxyfen.

Pyriproxyfen is used to eliminate the larvae of the mosquitoes that spread Zika, which include the female Aedes aegypti mosquito, Zika’s primary vector. The pesticide is introduced into the drinking water in some areas of Brazil.

The research team explains that pyriproxyfen is a juvenile hormone analog that regulates an insect growth, development, and reproduction. This substance is cross reactive with retinoic acid, which has been known to cause microcephaly.

NECSI urges more investigations into this health problem. Other researchers include experts from Argentina, Brazil and the Swedish Toxicology Sciences Research Center

The World Health Organization insisted earlier that pyriproxyfen does not affect pregnancy or the growth and development of a fetus. The health agency also stated that similar analysis conducted by the US Environmental Protection Agency and other EU institutions also found no link between the pesticide and microcephaly.