The mosquito is by some way the deadliest animal in the world. In terms of the number of human victims they claim each year nothing comes close, not even humans.
Certain species of the midge-like insects can carry extremely harmful diseases, which are transmitted when they feed on human blood. The most infamous and deadly is of course malaria, but there are many others.
Dengue fever – also known as breakbone fever – is one. It is a viral infection usually found in tropical and sub-tropical climates, affecting 50-100 million people every year. In most cases, it causes a flu-like illness and severe joint and muscle pain, from which it gets its graphic nickname.
However, the fever can develop into a potentially lethal complication called severe dengue. This is a leading cause of serious illness and death among children in some Asian and Latin American countries.
Each year, an estimated 500,000 people require hospitalisation because of severe dengue, with the majority being children. About 2.5% of those affected die.
“Dengue fever is a very unpleasant, frightening disease. There’s no medication and there’s no vaccine,” said Hadyn Parry, chief executive of the Oxford-based biotech company Oxitec.
Many countries have been fighting a long, losing battle against the aedes aegypti mosquito, the carrier of dengue. It is tiny yet distinctive, identifiable by its bright white stripes. Its name means ‘out of Egypt’. Carried from North Africa by men, the adaptable menace can also spread yellow fever and the chikungunya virus – an emerging and untreatable threat.
Where the mosquito goes, dengue is never far behind. The Portuguese archipelago of Madeira found their first aedes aegypti in 2005. A major dengue outbreak followed in 2012.
Around the world, cases have risen thirtyfold in the last fifty years. Traditional pesticides have proved ineffective and even harmful.
Oxitec present a pioneering alternative. Their method, which has been piloted and approved in Brazil, uses genetic engineering to control mosquito populations in a precise and environmentally friendly way.
They produce a lab-grown strain of sterilised male mosquitos to be released into the wild. Only females bite. Males lack the inclination and even the anatomy to feed on humans. When freed, the males simply track down their blood-sucking love-interests and mate. The resulting offspring inherit genes that act like a ticking time bomb, and die before they reach adulthood.
“If you do this enough times, you crash the population,” Parry explained.
Trials in Brazil, the Cayman Islands and Malaysia have shown that mosquito numbers can be reduced by more than 90% within months.
The approach is remarkably effective and entirely species specific. Pesticides dispersed in toxic fogs kill indiscriminately, damaging delicate ecosystems. Oxitec’s method, Parry explained, is “self-limiting”.
“Every single one of our mosquitos is only going to do one of two things. Its either going to find a female, mate with her, die and produce offspring that will die. Or, he won’t find a female and he’ll die anyway.
“There’s nothing that spreads into the environment. Nothing is left in the environment.”
The usual GM concerns – fears that genetic meddling can pass through the environment and the food chain – do not apply.
“What is interesting about this is the idea that people conjure up when they think about genetically engineered things, they tend to think about crops,” Parry said.
“Crops of course persist in the environment and their genes can spread, but this is the exact opposite. You’re dealing in sterility.
“It’s a dead end.”
Parry admits that Oxitec has taken heat from pressure groups opposed to genetic modification outright. But from the general public, in countries blighted by dengue, the reception is overwhelmingly positive.
“At the end of the day, people don’t like getting ill. The mosquito is nobody’s friend,” he said.
The commercial license Oxitec has recently obtained in Brazil is the company’s first – the first of its type in the world, no less – but Parry hopes to gain many more.
Regulators are keen, and not surprisingly. Oxitec estimate that dengue costs the global economy around $5 billion (£2.92bn) every year. Brazil alone spends around $1 billion (£580m) trying to control it. Discussions are also ongoing regarding outdoor trials elsewhere, from Florida to India.
Beyond aedes aegypti, Parry said he would like to adapt his method to take on anopheles and culex mosquitos, the vectors of malaria and West Nile virus.
Oxitec are also currently developing species of agricultural pests, swapping the battle against disease for the battle for food security.
“We think it has huge application in agriculture too – particularly where you have one main dominant pest,” Parry said.
“For example, olives. Olives are predominantly attacked by the olive fly. The olive fly can devastate the olive crop. In a case like that our approach would work very well indeed.”
First on the agenda though, is commercialisation in Brazil. Oxitec’s first factory in Brazil will open shortly. Soon, customers – local authorities and governments – will be able to purchase Oxitec’s services.
All of this has been made possible by the completion of a recent £6.1 million investment round. Existing Oxitec shareholders, including Oxford Capital Partners and the University of Oxford, completed the fundraising alongside private investors from around the world.
Parry explained that these supporters – “typically international, seasoned businesspeople and high-net-worths who understand dengue fever and environmental issues” – have helped with more than their money.
“We deliberately went out to try and get investors from around the world – from Brazil, Argentina, Asia – because it’s a contact point in those markets. It is very helpful for us.
“Some are very engaged and email me all the time. We have a very good relationship with our shareholders.”
The exit for these shareholders will come with an eventual IPO, but for now Parry eyes organic growth while building the business. With enquiries pouring in, Oxitec is primed for success.
The future looks bright for Oxitec, decidedly less so for aedes aegypti.
Photo: U.S. Department of Agriculture via Flickr