Oxitec developed an insect-based biological control system for safe and sustainable control of insects that transmit disease to humans and destroy crops. Oxitec is a spinout from University of Oxford and is a subsidiary of Intrexon Corporation which develops biologically-based products through its two operating units, Intrexon Health and Intrexon Bioengineering.
Oxitec engineers a variety of insects, from mosquitoes that transmit disease to humans to moth caterpillars that damage crops, with a self-limiting gene. The company claims on their website that when male insects are released, that their offspring are prevented from surviving to adulthood, but they have also reported that about 3% of their offspring survive in lab tests.
The company is developing genetically modified (GM) mosquitoes to suppress populations of natural mosquitos that carry viruses that cause disease in humans such as Zika and dengue. Oxitec’s strategy is to introduce male Aedes aigypti mosquitoes engineered to carry a gene that is designed to prevent their offspring from reaching adulthood.
A team of independent researchers analyzed an early trial of Oxitec’s technology and reported in September 2019 that some offspring of the GM mosquitos survived and produced more offspring that made it to sexual maturity. That local mosquitoes inherited pieces of the genomes of the GM mosquitoes caused some alarm to be raised. However no evidence was presented in the study that the hybrid mosquitoes endanger humans more than wild mosquitoes. Oxitec asked Nature Research, which publishes Scientific Reports, where the study was published, to “address the range of misleading and speculative statements”. The journal added an editor’s note on the paper which said its conclusions “are subject to criticisms that are being considered by editors”. One of the speculative statements was that genetic mixing could have made the mosquito population more resistant to insecticides or more likely to transmit disease.
Oxitec conducted pilot releases of GM male mosquitoes in Brazil, Malaysia and the Cayman Islands. Their lab tests had shown that roughly 3 percent of offspring could survive but as these offspring were often sickly in the lab, they did not know whether they could produce progeny. From 2013-2015 Oxitec released about 450,000 GM male mosquitoes per week in a field trial in Jacobina, Brazil. The company reported that the overall mosquito population was reduced by about 90 percent. They found the between 5-60% of mosquitoes collected in neighborhoods in the area had some DNA from the Oxitec strain in their genome and once case as much as 13% of its genome was from the Oxitec strain.
In Florida, residents have opposed proposals by Oxitec to release their mosquito strain. In September 2019 the U.S. Environmental Protection opened a monthlong window for public comments on releasing Oxitec’s mosquitoes in Florida and Texas.
Oxitec had developed an additional strain of GM mosquitoes designed to spread the lethal gene more effectively. With this strain female offspring do not survive and males survive to pass on the lethal gene. In a field trial in Brazil, the second-generation mosquitoes caused local populations to drop by up to 96%.