Teenage Mutant Killer Insects

By Lauren Hoskin

Each year there are an estimated 50-100 million cases of Dengue fever reported worldwide. This potentially life-threatening disease is principally transmitted through the Aedes aegypti mosquito. Up to now, techniques to control the disease have failed since A. aegypti are difficult to eradicate. Dengue is a massive problem throughout Southern and South America and across Asia.

In Greece and Spain, a problem of a completely different nature prevails. Olive fly is the primary pest of olive production, regularly wiping out whole crops. The olive industry in Greece spends around £30 million annually on controlling the pest. However, the flies are now becoming resistant to insecticides, which at the moment are the main form of control.

What do these two problems have in common? Both diseases could potentially be controlled using genetically modified (GM) insects whose offspring are destined to die before they reach adulthood.

Olive Fly

GM insects look like a promising approach. The technique is more environmentally friendly and longer lasting than pesticides. Additionally, no toxic chemicals are produced in the insect’s bodies and the genetic material cannot be transferred through ingestion so this is good news for food chains.

It’s not all good news though, as Florida Keys residents have pointed out. Unsurprisingly, releasing hoards of mutant insects into people’s home towns turns out to be a rather contentious issue.

To rear the modified insects, scientists have made use of a clever gene control system. Insect eggs are modified to contain a lethal gene which produces a protein called tTA. This protein acts as a control switch for many other genes. If left alone, tTA causes the cellular machinery to go wild, disrupting the normal function of the cells and causing female insects to die.

However, giving GM insects the antibiotic tetracycline prevents the protein from causing havoc, meaning insects can live as normal. This allows researchers to breed many generations of males in labs, but once released tetracycline will not be readily available and all offspring will die.

Importantly for this process, only male GM mosquitoes can be released since they do not bite humans. Once set free, modified males mate with wild females, producing offspring that will never breed. Trials on the Cayman Islands and in Brazil have reported success, suggesting feasibility for the technique.

However, there are many aspects that must be considered before the technology is put to practice. For instance, it is possible that lab-reared males may not be as fit, might not adapt well to new climates or could have different mating patterns to wild insects.

Oxitec, the company behind the technology, is currently awaiting a decision on an olive fly trial in Spain. Likewise, an operation to reduce the number of A. aegypti mosquitoes in Florida Keys could go ahead in the 2014. Many people are sceptical due to a shortage of independent peer-reviewed research. Yet if successful, this technique could solve a lot of problems.