Fighting Aedes aegypti Mosquitoes in the Cayman Islands

December 6, 2016

Devastating diseases attributable to several arboviruses transmitted by female Aedes aegypti mosquitoes pose an increasing threat to global public health as well as to tourism. With respect to the latter, the World Bank has estimated that in Caribbean and Latin American countries the economic impact from just one of these viruses, Zika, could reach $3.5 billion in 2016.

One place reliant on tourism that has been impacted by Aedes aegypti is the Cayman Islands.

To reduce the number of Aedes aegypti, the Cayman Islands Mosquito Research and Control Unit (MRCU) and Oxitec have begun the initial stage of an intended multi-phased programme deploying Oxitec’s OX513A self-limiting mosquito to suppress wild Aedes aegypti across Grand Cayman, the largest of the three Cayman Islands.

Oxitec’s Friendly™ male mosquitoes mate with wild females and pass on the self-limiting gene to offspring which die before reaching adulthood. Oxitec’s mosquitoes also die within days resulting in a solution that does not persist in the environment which can lead to significant declines in the local Aedes aegypti populations.

“We believe this environmentally friendly tool can greatly reduce the population of Aedes aegypti in Grand Cayman,” said Dr Bill Petrie, Director of MRCU.

MRCU and Oxitec have a history of working together, dating back to 2009 when they performed the world’s first Aedes aegypti suppression trial using Oxitec’s self-limiting mosquito in the Cayman Islands. That trial reduced the target mosquito population by 96% in less than one year in the targeted area.

“We have wanted to remove this invasive pest for a long time, but this has proven very difficult using currently available tools, so we have been looking for new approaches. The decision to deploy the Oxitec technique comes after the success of a peer-reviewed trial,” said Dr Petrie.

The release programme, known as the Friendly Aedes aegypti Project, started in late July 2016 in West Bay, an area of Grand Cayman that is a hotspot for Aedes aegypti.

Cayman poll

An opinion poll conducted before releases began revealed that 68% of Grand Cayman residents are worried or very worried about mosquito-borne diseases and many think it is important to test new tools against the Aedes aegypti. It is therefore not surprising that a large majority of residents (69%) support the Friendly™ Aedes aegypti Project.

“The survey has revealed overwhelming support for the programme, and the communication campaign will be continued during the project to keep residents informed”, said Oxitec Cayman Project Manager Dr Renaud Lacroix.

In the project area in West Bay, larvae collected from the field are already showing the fluorescent genetic marker that is associated with the self-limiting gene. This means that the released males are indeed mating with females in the wild, and are passing on the self-limiting gene to the offspring.

Fewer Aedes aegypti may limit the threat of the diseases they spread, which include Zika, dengue, chikungunya and yellow fever. If Grand Cayman is free of these invasive mosquitoes, it may help keep the island’s people safe – and protect tourism.

Header photo: Kenroy Millwood and Giselle Johnson, production and field assistants with Oxitec, conduct “Friendly” mosquito releases in West Bay, Grand Cayman. Credit: Catherine MacGillivray, Cayman Islands Government Information Services