Sunday, January 31, 2016

Could GM mosquitoes be responsible for Zika microcephaly?

Since my post about ZikaVirus (ZV) here yesterday yesterday, I have been discussing the matter intensively.

Two things have emerged. 

One is that the idea of actually eliminating disease-carrying mosquitoes is highly contentious, so much so that it is not a good idea to discuss at this stage. Better to think in terms of reducing mosquito populations and opportunity for them to contact humans.
Second is that there is a suspicion that the cases of microcephaly were first recognised in the same part of Brazil that the Oxitec genetically modified mosquito (GMM) was released in 2012. IN fact the GM release was 300km away from the place Zika appeared, and separated by 2 years. 

People are concluding that somehow the GMM contributed to the microcephaly cases. The idea is running on social media, and RT has carried it. FoE USA have also expressed concern that in the presence of tetracycline antibiotic, the GMM progeny will have a survival rate of 15%. The Ecologist carries a write-up of the GM theory.

So could the GM technique somehow be responsible for a change in the virus that causes it to cause microcephaly? This is unlikely, but the question deserves an answer.

It is possible that ZV has  always caused microcephaly, but the association has not been noticed until now.

It is impossible that the Oxitec process could affect the virus gene, since the GM process is aimed at DNA, whereas the virus is an RNA organism.

ZV was first found in a monkey in Uganda in 1947, and was unremarkable until 2007 when it spread to the Pacific islands. Air travel facilitated this jump, and global warming is in the process of extending the mosquito's range.

The WHO Director General reports that neurological disorders were noticed after an outbreak in French Polynesia in 2013. The WHO D-G also adds "Arrival of the virus in some places has been associated with a steep increase in the birth of babies with abnormally small heads and in cases of Guillain-Barre syndrome".  French Polynesia had an outbreak of ZV in 2014-15. Health authorities found 17 central nervous system malformations, and four of these tested positive for ZV. Oxitec was not deployed in Polynesia. This is sound evidence that ZV does microcephaly on its own, without help from GM.

To get a definitive understanding, researchers need to look methodically at the incidence of microcephaly in other areas that have suffered Zika virus outbreaks. Research can also compare the incidence of microcephaly (and maybe Guillain Barre) rates in the Cayman Islands and other areas of Brazil where your GMM have been introduced, and compare the figures with outbreaks where there are no GMM.

These studies are likely to take at least a year.

In the meantime the basic position is that we need to defend ourselves against Zika virus by taking action at every level of technology, including antivirals, vaccines, and measures against the vector, including targeted pesticides and the Oxitech technique if it can be cleared of harmful effects, but above all we must prioritise action by local communities in eliminating unnecessary standing water.

The slight cloud over GMM just emphasises the need for a full-on programme of source reduction - reducing any stagnant water. This deserves a post of its own (here).

This post has been updated 1/2/16 & 2/2/16, 5/2/16
More on this from Mark Lynas in the Guardian

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