In December the Brazilian regulatory authority Comissao Tecnica Nacional de Biosseguranca (CTNBio) formally approved the next phase of using Oxitec’s Aedes aegypti product strain, OX513A, to help combat the wild mosquitoes that spread dengue. In this next phase Moscamed will treat the town of Jacobina in Bahia state, populated by around 80,000 people, with a planned start in April.
During 2012 Moscamed carried out two very successful demonstration trials in nearby suburbs of Juazeiro. In the treated areas the wild populations of the dengue mosquito were reduced by over 85%.
Since the authorisation from CTNBio to proceed was received, detailed planning has been in operation, with numerous activities being carried out in parallel. Staff needed to be hired and trained, equipment for rearing and release purchased, and detailed planning on production and release put in place. An essential component of the next phase is to make sure local residents are fully informed and supportive of the project. Teams from Moscamed have visited schools, community groups, and made door to door visits. Local radio in a particular is a useful media to help inform the public.
Aldo Malavasi, President of Moscamed, commented that ”This is a very exciting project for the area. Dengue is a major health challenge for us. Brazil is leading the world in deploying this new approach to combat mosquito-borne disease. The response from the public and the results achieved to date have been excellent. Last year we conducted two very successful demonstration trials and built a factory capable of rearing sufficient mosquitoes for this phase. So now we are scaling up to the next level.”
The project is a partnership between Moscamed and the University of São Paulo (USP). It has the support of the Secretary of Health of the State of Bahia, the Secretary of Science and Technology of State of Bahia, the City of Juazeiro, and the Ministry of Health.
In two separate but related surveys conducted by Professor Mike Cobb (North Carolina State University), residents of Key West and the entire Florida Keys were asked about their views toward using genetically engineered mosquitoes to control the species of mosquito that spreads dengue. In both studies, a majority supported use of GE technologies to control the mosquitoes. More importantly, only a small percentage of respondents in either survey were opposed; the same percentage, or higher, were neutral rather than opposed.
One study involved person-to-person interviews whilst the other was conducted through a mail survey.
The reports conclude that ‘’A majority of residents supports the use of GE technologies to control mosquitoes and think it is safe. More respondents said the GE approach is safer than using chemicals and insecticides.”
The summary and the two individual studies can be viewed on the NCSU website:
In a newly published paper in the journal ACS Synthetic Biology, Oxitec describe development of a new technology for the control of moth pests. The pink bollworm and the diamondback moth are two of the biggest pests of cotton and brassica (cabbage, broccoli, oilseed, etc), respectively. Both continue to plague farmers, whose efforts to control them are hampered by the insects’ ability to develop resistance to the insecticidal tools used against them.
The new technology enables the production of large numbers of male moths for release over affected crops. Mating with wild females results in the absence of female progeny: by reducing the number of female moths on a crop, the pest population’s potential for expansion is hampered, and numbers crash.
As the method’s mode of action relies on male moths mating with females, its action is exquisitely species-specific, thereby minimising off-target ecological effects or chemical residues. Another benefit will be that releasing these Oxitec males can have a diluting effect on insecticide resistance genes. This potentially powerful means of resistance management has been modelled by Oxitec and Oxford University scientists, and could become a key component for sustainable pest management. Any method that safe-guards the effectiveness of control tools can only be a good thing, as farmers are currently faced with a diversity of pest problems on their crops, but often with a diminishing selection of available methods to combat them.
The strains have undergone characterisation in the laboratory, and are now ready for testing in the field. Oxitec is seeking partners in countries where these moths hamper agriculture, with a view to demonstrating their potential for environment-friendly crop protection.
Invasive pest species are a serious and growing problem for public health, agriculture and regional ecology, as we discussed in a previous issue of the newsletter (May 2012). The dengue mosquito, Aedes aegypti, is one such invasive pest. Native to part of Africa, it is now widespread over tropical and non-tropical regions of the world, and its persistence has led to a massive rise in dengue cases in recent years. Current control methods struggle to cope, as the mosquito chooses diverse small breeding sites, which are very common in urban areas, and insecticide application methods are not sufficiently targeted.
Oxitec has demonstrated the success of its technology against the Aedes mosquito. In the Caribbean and Brazil, releases of Oxitec male mosquitoes (only the females bite) resulted in the wild populations crashing by 80-85%. As Oxitec’s technology relies on the mate-seeking behaviour of male mosquitoes, this more targeted approach should aid eradication attempts. These results have prompted the question – ‘can this approach be used to eliminate an invasive pest from an area?’ We believe the answer is ‘yes’ and this is would be greatly facilitated if the area, and hence target insect population, is isolated – such as on an island – so that efforts aren’t hampered by regular immigration of the pest from neighbouring areas.
In fact this principle has been demonstrated against the tsetse fly, which transmits deadly human and cattle diseases. This fly was eradicated from the main island of Zanzibar, East Africa, using the Sterile Insect Technique (SIT). The island showed strategic promise as it is located around 25km from the mainland, with a very low probability of tsetse flies re-infesting the island. Successive releases of sterile male flies, coupled with targeted use of insecticide, led to the flies’ eradication, with consequent benefits for cattle farmers since the 1990s. In this case the sterility was induced by radiation.
For the Aedes mosquito, Easter Island shows strong potential as a target for eradication of this invasive species. The nearest inhabited neighbour is 2,075 km away. At such an isolated location, successful eradication of the disease vector by release of Oxitec’s mosquitoes would likely be long-lasting. Post-eradication, low-level releases of Oxitec male mosquitoes at likely entry points, such as ports, would add a further level of protection against re-invasion. However while Easter Island is far from its neighbours, isolation need not be by long distances. The adult Aedes mosquito only flies up to 200 metres in its life so the isolation barrier does not need to be so large.
Where the Aedes mosquito goes, dengue can follow. The Atlantic island of Madeira, part of Portugal, has been home to this mosquito since only 2005. Prior to that year this insect has not been reported on the island. But once established it is near-impossible to remove by conventional methods, meaning that once an infected person enters the area an outbreak can occur. So, only 7 years after the insect was first reported Madeira suffered a dengue epidemic. On 3rd October 2012 two cases of dengue were laboratory-confirmed. By November 25th 1,891 probable cases had been reported and this exceeded 2,000 by the end of December. It remains to be seen what measures will be taken to curtail the dengue threat in Madeira but with our approach we consider an island could realistically target ridding itself of the pest removing the threat of disease and consequent economic loss through tourism decline or lost work through illness. Once removed, good monitoring could be put in place to pick up any signs of re-infestation in future years.
An insect that can fly only a short distance is not a ‘natural’ invader. In an island context the pest is almost always inadvertently introduced by man and it is the presence, rather than the removal, that is the key change to the local eco system.
Oxitec’s technology relies upon released male insects seeking out and mating with their wild female counterparts. Population control by successive releases in an area results from the fact that offspring of such coupling are not viable in the wild. It’s a bit like a honeytrap for the female of the species. For this to work, though, the male insects need to be able to find their prospective mates in the first place. Insects have developed an array of powerful methods to help this happen, even from afar.
For mosquitoes, the secret lies in their antennae and something called the Johnson’s organ, which work together to make mosquitoes the most sound-sensitive of all insects. A male mosquito will be attracted to the sound of the wingbeat, or ‘song’, of females of the same species. When they meet, the two courting mosquitoes adjust their wingbeat frequency to a shared harmonic. If the male sings well, then, the female will accept him as a suitably attractive mate.
Moths find their mates through chemicals: the female releases pheromone, usually at dusk, to ‘call’ for male mates. The male antennae are so sensitive to these chemicals that they can detect a female from kilometres away. He will then follow the ‘plume’ of pheromone until he reaches his intended mate. These pheromones are species-specific: that emitted by the female of one species will not be attractive to males of another species. This strategy has been used with some success against a number of problem moths. The sex pheromone of the cotton-damaging pink bollworm (Pectinophora gossypiella), for example, was one of the first to be characterised and synthesised. Farmers now use the synthetic version of the pheromone as bait in monitoring traps (to catch males) or for mating disruption (artificial sources of the pheromone result in male confusion).
In fruit flies, the picture is generally a little different. Males need to perform specific acts of courtship, sometimes next to competing males, to win the favour of a female fly. The males of the Mediterranean fruit fly (Ceratitis capitata), for example, gather in the late morning and early afternoon in the canopies of trees. After fighting for the prime location on a sunlit leaf, they emit a pheromone attract females. When she arrives, the dominant male vibrates his wings to waft an enticing pheromone blend towards her. Sometimes this fails to entice her, and she will move on to the next male, and the process continues until she has met a suitably attractive fly.
This overview illustrates that insect mating behaviour is perhaps more complex and subtle than it might first appear. For Oxitec’s pest control strategy to achieve its objective, the male insects that it releases into the field must therefore be able to find a mate and be as attractive to her as would wild males. In short, we aim to produce male insects that behave just as they would in the wild.
In November our CEO Hadyn Parry gave a TED talk in London explaining Oxitec’s approach to controlling the mosquito that spreads dengue fever. The talk has proved very popular and we have received a great many emails from people in dengue-affected countries asking if our approach can be used in their region. This talk can be found at: http://www.ted.com/talks/hadyn_parry_re_engineering_mosquitos_to_fight_disease.html
Oxitec are a ‘Fast company’! We have been named as one of the world’s most innovative companies by Fast Company magazine. We are not sure of how the nomination came about but thank you to Fast Company for the recognition.
The BBC World Service have reported on the potential of our approach in reducing the threat of dengue fever. Martin Vennard’s article focuses on the plans by the Florida Keys Mosquito Control District in the USA to evaluate Oxitec’s approach for controlling mosquitoes that could cause a dengue epidemic. This article can be found at http://www.bbc.co.uk/news/world-us-canada-19091880 Jennifer Kay of Associated Press also reports on the plans in the Florida Keys http://bigstory.ap.org/article/gene-altered-mosquitoes-could-be-used-vs-dengue Oxitec are currently working with the Food and Drug Administration (FDA) who are the lead regulator in the USA for our mosquitoes.
TIME magazine have chosen to focus on Brazil rather than Florida and report on the very successful trials there. For the TIME article follow this link http://healthland.time.com/2012/11/09/how-mutant-mosquitoes-are-fighting-dengue-fever/#ixzz2CIib1XYQ
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