Say hello to OX513A, the Genetically Modified (GM) mosquito, a new weapon against the mosquito that carries the Zika virus.
While Republicans wring their hands and play the blame game, the FDA has approved a test trial of the GM mosquito in Key Haven in the Florida Keys. Full scale deployment will depend on local officials and will likely occur after November.
OX513A will be used to control the population of the Aedes aegypti mosquito, the primary carrier and transmitter of the Zika virus, which has made its appearance in Florida.
OX513A, a creation of the British company Oxitec, is a strain of the Aedes aegypti mosquito. It’s DNA contains a synthetic self-limiting gene, which causes production of a protein that gums up the molecular machinery of mosquito cells, thereby killing them in a few days. Think of OX513A as a mosquito with a slow-release poison pill built into its cells. But these mosquitoes can be kept alive by feeding them a steady dose of the antibiotic tetracycline. Tetracycline suppresses the action of the inserted gene. That’s how the mosquitoes are bred and kept alive in the laboratory.
For deployment, a swarm of adult male OX513A mosquitoes are released into the environment. Male mosquitoes do not bite humans and do not spread disease (they feed on nectar, not blood). The OX513A mosquitoes impregnate female Aedes aegypti mosquitoes and die within a few days. The offspring, male and female, inherit the gene and consequently die before they reach adulthood, since there is no natural source of tetracycline. After multiple deployments, the mosquito population diminishes.
The mosquito control effect is nontoxic and species-specific, as the OX513A mosquitoes are Ae. aegypti and only breed with Ae. aegypti. The result of the self-limiting approach is that the released insects and their offspring die and do not persist in the environment.
Ingenious! Effective! No dangerous pesticides are used that affect humans or other organisms. There is no proliferation of the synthetic gene as each mosquito that carries the gene dies.
Open field trials of OX513A have taken place in the Cayman Islands, Panama, Brazil and Malaysia. This technique has also been used with agricultural pests.
See www.sciencenews.org/... and www.fda.gov… for more info. on the Florida trial.
Dangers and Concerns
Are there any dangers? Will the loss of the Ae. aegypti mosquito disturb the balance of nature and affect the population of other species, such as mosquito predators? Ae. aegypti is an invasive species, so there are few concerns on that front. One possible danger is that the loss of the Ae. aegypti mosquito may cause other mosquito species to proliferate, which carry similar germs and viruses. Another concern is that the released swarm may contain some female OX513A mosquitoes which may bite and inject humans with cells that contain the modified gene and proteins.
Does this technique eradicate the Zika virus, even in a local area, given that it does not eradicate the mosquito population? Will this technique require periodic release of the GM mosquitoes, forever?
And of course, there are the unknown unknowns.
That’s why such techniques have to undergo extensive study and testing before they are deployed. OX513A was created way back in 2002. And has been deployed in many countries.
Additional Information on OX513A
The OX513A synthetic self-limiting gene is derived from E. coli and the Herpes simplex virus.
OX513A contains a second synthetic gene which produces a fluorescent marker protein to aid in detection of these mosquitoes.
OX513A eggs are produced in the UK for shipment to the Hatching and Rearing Unit (HRU) located in Marathon, Florida, where they are hatched and reared to pupae, fed on a diet that contains tetracycline. Male mosquitoes are separated from female ones during the pupae stage using mechanical sorting based on the difference in size between male and female pupae.
Conventional Methods for Mosquito Control
The Zika Virus
Zika virus (ZIKV) is a member of the virus family Flaviviridae and the genus Flavivirus. It is spread by daytime-active Aedes mosquitoes, such as A. aegypti and A. albopictus. Its name comes from the Zika Forest of Uganda, where the virus was first isolated in 1947.
Zika can be passed from a pregnant woman to her fetus. Infection during pregnancy can cause microcephaly, severe brain malformations, and other birth defects in newborns.
Zika infections in adults may result in rare cases of Guillain–Barré syndrome, an autoimmune disease disease. Recent studies in mice have shown Zika virus to attack adult progenitor brain cells, which serve to replace lost or damaged neurons throughout adulthood, and are also thought to be critical to learning and memory.
Here is an animation of the Zika virus and its structure, created by the team from Purdue University which was the first to determine the structure of the Zika virus.
Vaccine
As of March 2016, 18 companies and institutions internationally were developing vaccines against Zika, but none had yet reached clinical trials.
A phase I trial for a Zika virus vaccine began this week, but the vaccine won't be ready for at least another year and a half, according to Dr. Anthony Fauci, the NIH chief of Allergy & Infectious Diseases.
There are some concerns about Zika vaccines — the vaccine designed to protect patients against Zika could inadvertently provoke more cases of the autoimmune condition Guillain–Barré syndrome. www.scientificamerican.com/...
Further Reading
FDA OKs first GM mosquito trial in U.S. but hurdles remain — www.sciencenews.org/…
How the Self-Limiting Gene Works — www.oxitec.com/...
NIH begins testing investigational Zika vaccine in humans — www.nih.gov/…
The Extinction Invention — www.technologyreview.com/...
Draft Environmental Assessment for Investigational Use of Aedes aegypti OX513A — www.fda.gov…
Zika infection may affect adult brain cells, suggesting risk may not be limited to pregnant women — newswire.rockefeller.edu/...
Notes
* Diary main image courtesy www.planetainvertebrados.com.br/...
* This diary has been updated to capture some of the insights provided by astute readers in the comments section below