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Gene therapy

February 11, 2011

A study describes a new way to spread genes amongst mosquito populations that are resistant to serious diseases such as Malaria and dengue fever.

A mosquito poses on a man's hand
Scientists hope to limit the spread of mosquito-borne diseaseImage: picture-alliance /dpa

Malaria causes the deaths of more than a million children every year in sub-Saharan Africa alone.

The unrelenting fight against mosquito-borne diseases has seen many different approaches to reducing the mosquito population: from swamp-draining to the use of a wide variety of pesticides.

Now, a new study published this month in 'Genetics' proposes the use of genetic engineering in the fight against serious diseases such as Malaria and Dengue fever.

"Invariably with population suppression, the Mosquitoes just come back," said Dr. John M. Marshall - a researcher at Imperial College of London involved in the study.

Rather than simply trying to reduce mosquito populations, the so-called 'Semele' system describes a new way of spreading genes amongst the mosquito population that confer resistance to diseases such as Malaria.

Dual action

The system consists of two elements: a semen-based toxin and a female antidote.

In isolation, releasing transgenic males carrying this toxin will suppress populations by killing or rendering infertile wild female recipients. But, says Marshall, the beauty of this research is the introduction of transgenic females that have developed an antidote to the toxin:

"Even if the antidote is recessive, then the system displays, superior qualities – it spreads to 100% of the population," he said.

The malaria virus
Malaria causes the death of more than a million children in sub-Saharan Africa each yearImage: DW-TV

It is this symbiotic relationship between toxin and antidote that successfully propagates the anti-Malarial gene in insects such as mosquitoes.

Greek origins

The Semele system is named after a mortal female of the same name in Greek Mythology. After giving birth to an illegitimate child by the God Zeus, she died when confronted by his godliness.

"We choose the name," Marshall said, "As the system proposed here results in the death (or infertility) of females who are impregnated by transgenic males, but are not themselves transgenic," he continued.

Favorable qualities

In addition to these obvious benefits, the Semele system has proven especially favorable for early stage research, Marshall said: "This system has the ability to be easily confined which is really beneficial for risk management."

This means the system can be confined to an isolated population, such as a village for instance and it can be recalled easily in the event of unforeseen consequences.

In addition, the system is species specific, which means that the only the insect in question is targeted in distinction to pesticides for instance.

A mosquito
The practice of genetic engineering is controversial in the scientific communityImage: dpa

But, according to Marshall, this study does not claim to offer an alternative to pesticide use.

"Genetic engineering is an additional area," he said. "If you combine all the approaches, we will be able to wipe out Malaria collectively."


Genetic engineering remains a taboo topic in the scientific community and beyond, but it is important to keep an open mind Marshall said.

"It is an out-there idea," he said. "But the idea of genetically modified mosquitoes is beginning to gain popularity and acceptance in the scientific community."

This, in great part, has been due to successful projects involving genetically modified mosquitoes in the Cayman Islands in 2009 and most recently, a field study in Malaysia.

Most importantly, Marshall hopes this may help in the prevention of serious diseases.

"Ultimately, I hope that the application of these ideas will help move transgenic mosquito technology forward and thereby contribute to the many efforts to reduce the prevalence of Malaria and Dengue fever in disease-endemic countries."

Author: Sarah Stolarz
Editor: Stuart Tiffen