UK firm publishes results of Cayman mozzie test

(CNS): The results of a genetic experiment among mosquitoes which took place in the Cayman Islands two years ago have finally been published in a scientific journal. In 2010 millions of genetically modified Aedes aegypti mosquitoes were released in East End by the UK biotechnology company Oxitec Ltd as part of a research test related to controlling dengue fever. In a report published Monday in the journal Nature Biotechnology, the scientists say that the experiment wiped out 80% of the local mosquitoes which can carry the disease.  At the end of the 23 week test in conjunction with the MRCU, mosquitos had dwindled by four-fifths in the research site compared to the untreated area.

Dr William Petrie, Director of the MRCU, said incidences of dengue have grown rapidly in recent years and the only means of prevention is to target the mosquitoes which carry it.

“We need new tools in the fight against these dangerous pests, and today's publication shows that Oxitec's approach can provide that," he stated in a release.

Dengue, which is caused by a virus carried by the Aedes aegypti mosquitoes — though those in Cayman are not carriers — afflicts as many as 100 million people around the world each year. The virus can cause severe flu-like symptoms and fatal bleeding with around 500,000 people who develop the severe form dying.

Oxitec's Chief Scientific Officer, Luke Alphey, added that the report was an important result for the firm.

“We have developed our approach over a number of years and have conducted rigorous testing to ensure it is both sustainable and safe,” he said. “These data indicate that it is also extremely effective, as previous laboratory and modelling work had led us to hope. 80% suppression is an excellent result, especially as wild mosquitoes could migrate into the trial area — we should see even stronger reduction in larger or more isolated areas.

"We believe this approach can be used in many countries to offer a more effective, greener solution to controlling the Aedes aegypti mosquito and reducing Dengue Fever.”

During the Grand Cayman experiment the company used a technology to alter the DNA of the mosquito by inserting a copy of an altered gene. The modification caused the insects to produce excessive amounts of a protein disrupting their cell machinery. When the modified male insects were released they mated with wild females, and the scientists claimed the offspring died before reaching adulthood.

However, the experiment was not without its critics as environmental activists raised concerns that the experiments were not well monitored, did not follow accepted protocol in that the residents of East end were not consulted and the results are questionable.

In a press release in the wake of the publication in the science journal, GeneWatch UK said Oxitech had no clear baseline for the claims that it achieved an 80% reduction in the target population of mosquitoes.

“This poor quality paper pours cold water on the idea that Oxitec’s GM mosquitoes will be an effective way to tackle dengue” said Dr Helen Wallace, Director of GeneWatch UK. “Staff would be better employed using the well-established public health approach of removing mosquito breeding sites rather than in placing GM mosquito pupae at intervals across a site. Removing the flower pots and water containers where mosquitoes breed has the added benefit of reducing both mosquito species that spread dengue, not just one of them. It is hard to see how Oxitec can justify commercial releases of its GM mosquitoes based on such poor data.”

GeneWatch stated that Oxitec reports several different estimates of the reduction in the wild population of mosquitoes, ranging from 60% to 85% depending what comparisons are made. Because there is no baseline data on mosquito populations at the site, there is considerable uncertainty in the results.

“At different times, Oxitec moved mosquito traps from one location to another and changed the size of the release site, adding to difficulties in interpreting the results,” the activists claim. The NGO stated that releasing such large numbers of mosquitoes adds to concerns that the small percentage of surviving GM mosquito offspring and accidental releases of GM female mosquitoes could pose unnecessary risks.

The activists also warn that poorly effective approaches to reducing mosquito populations can actually increase the risk of the more severe form of dengue due to the loss of cross-immunity to different serotypes of the dengue virus.