The city of Jacobina, Brazil in the Bahia region was selected as the ideal area for a study designed to control disease-bearing mosquitoes. A recent report in the Science edition of DW described Jacobina as an arid, ecological forest in which the Ae. Aegypti, a lethal mosquito, cannot breed.
However, contrary to the original plan whereby all mosquitoes that were released, including their offspring, would have died, the genetically modified mosquitoes are breeding.
Third World Countries are Especially Vulnerable
Traditional methods of controlling the devastating toll on human health in third-world countries are out of reach for most people and generally ineffective for those who have access to drugs or insecticides.
Most scientists believe that their only hope is to control these infectious mosquitoes that transmit yellow fever, the Zika virus, and dengue fever through genetic manipulations.
The Initial Attempt
Oxitec Ltd., a UK-based biotechnology company, developed a strain of Aedes aegypti (OX513A) mosquitoes that were transgenically modified to harbor a lethal gene. The modification of the gene was engineered so that the initial descendants, called F1, would never mature and hence would not reproduce.
The strain of OX513A mosquitoes also includes a protein gene which is fluorescent and allows detection of type F1 offspring.
The Study Did Not Go as Planned
The scientists were aware that about 3 or 4 percent of the offspring resulting from OX513A matings would survive. They assumed that the surviving mosquitoes would be too weak to reproduce.
This was a miscalculation.
After analysis, Yale University researchers determined that the hybrid offspring are “sufficiently robust” and capable of reproducing. Further analysis showed that portions of the strain were transferred unintentionally.
The Result of Miscalculating
The scientists who conducted the study determined that the genetically modified mosquitoes were just as capable of carrying infectious diseases as they were before the modification.
The Ministry of Health had hoped that the study would result in a 90 percent reduction of the lethal mosquito population. The goal of the genetic modification was to produce infertile offspring. But eighteen months after the conclusion of the study, the mosquito population was back to where it had started.
The study was published in Nature on September 10, 2019.
Now in hindsight, the scientists realize the urgency of a genetic monitoring program in any future trials to identify unintended outcomes.
Other Scientists Had Issued Warnings
Dr. Ricarda Steinbrecher emphasized concerns in her September 2010 report. Dr. Steinbrecher pointed out that the anticipated survival rate of 3 or 4 percent required further analysis prior to releasing the genetically modified mosquitoes. It appears obvious that Dr. Steinbrecher’s advice, as well as that of other scientists, was ignored when it should have been followed.
The team of Yale researchers expressed concern that the genetically-modified mosquitoes may become even more robust, which apparently was the case.
A Brazilian biologist who is generally critical of genetic engineering claimed that the release of mosquitoes occurred without any clarification.
Other scientists who have concerns about genetic engineering claim that Oxitec began the study without conducting sufficient studies which led to an uncontrollable situation.
The Zika Outbreak
The World Health Organization (WHO) formed its Emergency Committee in 2015 to deal with the Zika virus and its explosive spread in the Americas. The WHO warned of the possibility of the Zika virus reaching pandemic proportions. The WHO saw the correlation between the Zika virus and birth abnormalities.
In retrospect, it appeared that Zika just suddenly exploded. A small number of cases appeared in the Pacific and Africa in 2013. Cases began to show up in the Americas. By May of 2015 Brazil acknowledged one case of Zika virus but from then on the situation escalated drastically. The WHO suggests that the virus can also be transmitted unknowingly by humans.
At that time Brazil was considered the center of Zika’s outbreak. The scientists suspect Zika in about 4,000 cases of infants born with incomplete brain development.
Curiously, Oxitec announced that it had reduced the deadly Aedes aegypti population by over ninety percent.
Conversely, it appeared to many that the effort to control the lethal mosquitoes had backfired. Brazil responded to the outbreak by ordering 200,000 soldiers to the region.
The Tetracycline Paradigm
Under ideal circumstances, the Oxitec OX513A mosquitoes are engineered so that most of their offspring die before maturity. That is as long as tetracycline is not in the picture while the strain is developing.
An unclassified document by a committee on agriculture and trade disclosed that Brazil is listed as number three worldwide for use of tetracycline in animals slaughtered for food.
It is estimated that animals do not absorb about seventy-five percent of antibiotics from their food. Therefore, the unabsorbed tetracycline is excreted in waste.
A 2012 internal, confidential Oxitec document disclosed that tetracycline, even in small amounts, has the effect of repressing engineered lethality.
The tetracycline paradigm begins with a description by Oxitec that after testing, they discovered that researchers used cat food to feed OX513A larvae. The cat food contained chicken.
Tetracycline is used to avoid infections in chicken. It is used especially in mass-produced chickens that are used in animal food. Although the chickens are heat-treated, some of the tetracyclines remain.
Therefore small amounts of tetracycline ended up being added to the larvae which repressed the engineered lethal system.
Dr. Steinbrecher suggested that it is possible for a genetically modified sub-population of Aedes mosquitoes to potentially develop and be capable of flourishing even if there were no further releases of mosquitoes that still have the gene intact.
Ironically, an MIT Technology Review stated that if there is another outbreak in the Western Hemisphere, countries including the United States would have “new reasons” to wipe out the virus through genetic engineering.
In November 2016 WHO announced the end of the Zika epidemic.
Were you one of the many people in the United States following the rise and fall of the Zika virus?