Published On: Wed, Jan 28th, 2015

Genetically engineered mosquitoes reduce dengue and chikungunya in Panama

Chikungunya virusOXFORD, England -- An outdoor pilot trial of an engineered strain of the Aedes aegypti mosquito, which transmits the dengue and chikungunya viruses, has resulted in a reduction of over 90% in the local population of the mosquito.

The study took place in a neighbourhood of Nuevo Chorrillo, a residential suburb of the Arraiján District, west of Panama City. The 10-hectare urban area is home to approximately 900 residents and contains a school and several small businesses. Two similar neighbourhoods nearby were monitored for comparison purposes.

Male Oxitec OX513A mosquitoes, termed 'friendly mosquitoes' by many residents, were released throughout the study area on a regular basis. Whenever these males, which cannot bite or transmit disease, mated with local female Aedes aegypti, their offspring died before adulthood. This reduced the population in successive generations of mosquitoes until, after only six months, the reduction was over 90% relative to the comparison sites.

Hadyn Parry, CEO of Oxitec commented: "We have been delighted to work with the Gorgas Institute - as they are a world-leader in developing advanced approaches for controlling disease-carrying mosquitoes. Achieving over 90% suppression of the local Aedes aegypti population is particularly pleasing because the project took place going into the rainy season, when mosquito numbers rise significantly. Furthermore, these results are wholly consistent with those from studies by collaborators in the Cayman Islands and Brazil. The Oxitec solution is far and away the most sustainable way to control Aedes aegypti since it affects only the target species and does not persist in the environment. It provides an urgently needed new tool that can be used in conjunction with existing programmes."

The pilot was conducted by the Gorgas Institute with the OX513A eggs and technical support coming from Oxitec. Prior to the pilot, approval was obtained from Panama's National Biosafety Committee, and from the Ministries of Agricultural Development and Commerce and Industry. In addition, extensive community engagement was carried out locally.

Nestor Sosa, director of the Gorgas Institute, said: "Panama, like many countries in the region, has been experiencing a dengue epidemic and more recently we are seeing a new virus, chikungunya, coming to our country. Aedes aegypti is the main vector of both these debilitating diseases for which there is no medication or vaccine. Chemical based approaches have not been able to control this mosquito sufficiently well to prevent the epidemics that Panama has experienced. The pest reductions achieved using the Oxitec solution go far beyond what is practical with conventional insecticides and therefore gives real hope of providing people with vitally needed protection from dengue and chikungunya."

Dengue is a debilitating disease spread by the Aedes aegypti and Aedes albopictus mosquitoes, with Aedes aegypti being the primary vector in the Americas and hence the priority for control. Dengue causes a range of severe flu-like symptoms, and is sometimes in extreme cases, fatal. Dengue is estimated by the World Health Organisation (WHO) to affect 50-100 million people a year; a recent publication in Nature estimated the actual number of infections to be 390 million. Dengue incidence is increasing rapidly around the world and there is currently no vaccine or specific medication. In 2013, Panama had over 3,000 reported dengue cases – more than triple the number in 2012 and the country is still epidemic for dengue.

According to the WHO, at present the only way to combat dengue is to control the mosquitoes that spread the disease.

Chikungunya is a different virus transmitted by Aedes mosquitoes. In late 2013, the first local transmission of chikungunya virus in the Americas was identified in Caribbean countries. The USA Centre for Disease Control (CDC) estimates that there have since been one million cases in the Americas. Chikungunya can cause severe muscle pain and cramps, and over 10% of people can develop persistent arthralgia for a number of years after acute infection. Like dengue it can only be transmitted by the bite of an infected mosquito.

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