In our earlier blog post we described how a laboratory in the UK has developed a genetically modified male mosquito which could help stop the spread of dengue. With extensive research in the lab and numerous field trials, this technology is now in operational use in one city in Brazil – where it has already achieved 79% suppression of the Aedes aegypti mosquito population.
Field trials in Brazil
Field trials, which involved the release of millions of the modified males, began in Brazil in 2011 with the Itaberaba neighborhood of Juazeiro seeing its mosquito population plummet by over 80% compared to an adjacent area.
A second trial, in the Mandacaru neighborhood, saw populations plummet by 96% within six months. “It typically takes about six months to achieve that level of control because it works on a generation by generation approach,” revealed Dr. McKemey, Head of Field Operations at Oxitec. “If half the wild females mate with Oxitec males, that means half of the next generation won’t develop. If you carry on releasing, then the same happens again. A mosquito generation is roughly a month, so you won’t see any immediate effect for at least that period of time and then there is a drop in numbers as each subsequent generation becomes affected by the males released.”
Six months into the trial the number of mosquitoes released was reduced four-fold. Dr. McKemey explained why. “For the initial phase you need to release large numbers, but once the population has dropped you continue releasing, but at a very low level, just enough to ensure that any remaining females mate with the modified males.”
Operational use in Brazil
2013 saw field trials move to operational use in the Brazilian city of Jacobina – a city of 79,000 inhabitants that, according to Oxitec, saw 1,647 dengue cases and two deaths due to it in the first half of 2012. “Our approach in Jacobina is to treat an area and then as we gain control in that area we move onto the next area,” Dr. McKemey told us. “In the first area, Pedra Branca, we have already achieved 79% suppression.”
Adequate production is key to the successful operational use of the modified mosquitoes. Social nonprofit organization Moscamed has increased production in their mass-rearing facility, meaning the area being treated can be increased. Once control is achieved in one area, the team can reduce the release rate and the extra capacity can be put to treating new areas.
In April 2014, Brazil became the first country to grant biosafety approval for the commercial release of these mosquitoes. The approval process assesses the safety of the technology and this regulatory conformation means a specific safety permit is no longer needed for each project. Oxitec is now working with the national health authorities in Brazil to obtain approval to sell it commercially.
Oxitec has recently set up its own mass-rearing facility in a city called Campinas, near São Paulo in south Brazil. The company is currently in negotiations with local authorities and vector control teams to launch new projects in the region.
Field trials in Panama, talks in Florida
Meanwhile field trials started in Panama earlier this year following approval for open release in the country. “We have been working with the Gorgas Institute in Panama tracking populations in two villages for two or three years to use as our baseline. From there we selected a further village that we are now working in,” says Dr. McKemey. According to Health Minister Javier Diaz, Panama reported 3,124 dengue cases in 2013, up from 899 in 2012.
Elsewhere in the Americas, the Florida Keys Mosquito Control District is evaluating the Oxitec technology. Dr. McKemey says that “despite having the top experts and best resources – helicopters and planes – the Keys have been really struggling to get on top of the Aedes aegypti mosquito. There have been a couple of outbreaks and they are highly concerned that it might get hold. We are working with the US Food and Drug Administration to get approval for a trial in an area of between 500 and 1,000 people.”
The company hopes that continuing field tests and increased operational usage will increase awareness of this technology and help them make a significant contribution to the fight against dengue.
What might be the risks in using GM mosquitoes in the fight against dengue and would the potential benefits outweigh these?