![The Aedes Aegypti mosquito transmits a variety of arboviruses such as Dengue Fever (DENV-1, DENV-2, DENV-3, DENV-4), Chikungunya (CHIKV), Yellow Fever (YFV), and also Zika (ZIKV), which have caused outbreaks within the wider Caribbean and other sub-tropical regions over the past decade.]()
The Aedes Aegypti mosquito transmits a variety of arboviruses such as Dengue Fever (DENV-1, DENV-2, DENV-3, DENV-4), Chikungunya (CHIKV), Yellow Fever (YFV), and also Zika (ZIKV), which have caused outbreaks within the wider Caribbean and other sub-tropical regions over the past decade.
There is a serious need for the creation of new technologies to combat the growing threat of the Aedes Aegypti mosquito in the wider Caribbean and in recent years, specifically the Cayman Islands. The Genetically Modified (GM) Mosquito has been heralded as that possible solution and 22-million will be released in the Cayman Islands over a period of 9-months in order to prove this theory, which according to the World Health Organisation (WHO) is showing much promise.
The reason the region has been placed on high alert is because they transmit a variety of arboviruses such as Dengue Fever (DENV-1, DENV-2, DENV-3, DENV-4), Chikungunya (CHIKV), Yellow Fever (YFV), and also Zika (ZIKV), which have caused outbreaks within the wider Caribbean and other sub-tropical regions over the past decade.
At present, all the existing mitigation tools used to combat this threat to the region as well as locally have become largely ineffective, and in the Cayman Islands the Aedes Aegypti have developed a resistance to the commonly used insecticide that is used in both aerial and terrestrial spraying.
Whereas dengue viruses are endemic throughout territories of the United States, including Puerto Rico and the U.S. Virgin Islands, most recently, focal outbreaks of locally transmitted dengue have occurred in Florida, Hawaii, and Texas. In 2005, DENV (Dengue) was considered a global public health concern.
Also in 2005, Chikungunya (CHIKV) emerged, first in the Indian Ocean but quickly spread and typically manifests as fever, joint pain, and rash. In 2014, 12 cases of locally acquired chikungunya infections were reported in Florida, according to the Centers for Disease Control (CDC). Chikungunya first appeared in the Caribbean in 2014 with the first major outbreak recorded in 2015.
![This diagram shows how GM mosquitos work]()
This diagram shows how GM mosquitos work
In 2007, Zika virus (ZIKV), which typically manifests as fever, joint pain, rash, and conjunctivitis, emerged for the first time outside Africa and Asia, in Yap State in Micronesia. Six years later, the virus caused a large outbreak in French Polynesia and then spread to other Pacific islands. In May 2015, autochthonous cases of Zika virus infection were confirmed in Brazil and by the end of that year, Brazil had declared an outbreak, and the virus had spread to several neighbouring countries, including Central America, Mexico and the Caribbean. The CDC says it is expected that Zika transmission will increase throughout the region escalating the incidence of infection in returning travelers and the possibility of local transmission.
Presently, a Yellow Fever outbreak was detected in Angola late in December 2015 and confirmed by the Institut Pasteur Dakar (IP-D) on January 20, 2016. Subsequently, a rapid increase in the number of cases has been observed. As of May 19, 2016, Angola has reported 2420 suspected cases of yellow fever with 298 deaths.
All of these abroviruses are transmitted by a specific mosquito; the Aedes Aegypti which is commonly referred to as “the yellow fever mosquito” and may be recognised by its distinctive white markings on its legs and a marking in the form of a lyre on the upper surface of the thorax.
The concept of the GM Mosquito is a new angle on an old technique, which emerged from the sterile insect technique (SIT) which was first developed in the United States and later in the Caribbean in the 1950s to combat and eliminate the screw-worm which was decimating livestock herds across the American South. At the time, red meat and dairy supplies were affected across Mexico, Central America, and South America.
Sterile Insect Technique proved to be a successful method of biological insect control, whereby overwhelming numbers of sterile insects are released into the wild. The released insects are normally male, as the females cause the damage usually by laying eggs in the crop, or, in the case of mosquitos, taking blood from humans. The problem identified with the Sterile Insect Technique was that radiation was used to create the insect, which in part impacted the overall health of the insects and was discontinued, however the theory was sound and provided the foundation upon which the more modern, GM Mosquitos are based.
The improvement to this technique, according to Dr Alan Wheeler, Assistant Director of Research and Development at the Mosquito Research and Control Unit (MRCU), can be found in what is described as a “dominant lethal gene” which allows the mosquito to mate with other female Aedes Aegypti but because it is sterile, the larvae that is produced die at the fourth stage of gestation and never emerge as adults; thereby reducing the overall population and subsequent spread of viruses.
Much hysteria has been created on the worldwide web as it relates to genetic modification suggesting “it is against God’s Will”, however according to Dr Wheeler, much of this criticism is unjustified and genetic modification has existed for centuries. “Look at dogs, for example, which no longer represent the animals that first appeared in the world but have been bred or genetically modified to produce the result that is desired in a much quicker time frame,” he said.
The genetic modification of mosquitos were developed by a UK company, Oxitech, who are partnering with MRCU in this initiative and are described as a pioneer in controlling insects that spread disease and damage crops, in a way that is sustainable, environmentally friendly and cost effective. Avoiding the previous sterilisation by radiation used in the former sterile insect technique, modifications are made with the insertion of two genes into the mosquito that make it sterile.
Dr Wheeler says the process is “incredibly environmentally friendly and if successful, there will be no need to spray insecticide which, in some cases, has proven to have negative impacts on humans, it is target specific to the Aedes Aegypti and not any other type of mosquito, which counters the argument that they will interrupt an important part of the natural food chain”, adding that “Aedes Aegypti are an invasive species and not indigenous to the Cayman Islands.”
Dr Wheeler accepts that biological control does not have a good history, drawing the example of Australia, where rabbits were first introduced for hunting, but because of the alarming rate of reproduction caused Australia to be over-run by rabbits which lead to the introduction of foxes to cull this threat. However soon after it was discovered that rabbits were too fast for the foxes and they thereafter adapted to hunting and killing local birds. Dr Wheeler says “the beauty of this process is that the mosquito’s are sterile and will not produce offspring which limits the negative impacts, and should any negative impacts be discovered as part of this 9-month trial process, they can be immediately removed from the population as easily as they were first introduced.”
Given than the GM mosquitos are bred to address specifically the Aedis Aegypti, it will not harm the other 36 indigenous species of mosquito such as the Black Salt-Marsh mosquito that has been identified as an important part of the natural food chain and is most commonly found after sunset and is responsible for most of the bites encountered in the Cayman Islands. The difference in this and the other 35 species found in Cayman is that no others carry the arboviruses such as Zika.
If the process of GM mosquitos is successful in Cayman it will not mean the eradication of all mosquitos but merely the disease transmitting mosquitos. This, if successful, will also have tremendous positive impact on the Cayman Islands tourism sector. “We actually receive several thousand calls every year from perspective tourists who are considering the Cayman Islands as their next vacation destination, but because the fear of mosquito-borne diseases are so real, many choose otherwise”, Dr Wheeler stated, while adding “imagine the economic windfall for the Cayman Islands if it could boast not just crystal clear water and white sandy beaches, but also that it boasts a disease-free zone from caused by the invasion of Aedes Aegypti.”
22 million GM mosquitos are scheduled to be released over a period of 9-months in the Cayman Islands as part of an ongoing experimental technique which will be closely monitored. The experiment is not exclusive to the Cayman Islands and are also being trialed in Brazil and Panama and other impacted countries, however if successful the programme will be expanded to include Cayman and other nations impacted by the outbreak of the arbovirus transmitting mosquitos. The mosquitos will not be modified in Cayman, but instead mosquito eggs will be imported by MRCU, bred in captivity in a laboratory environment where the males can be separated from the females, with only the sterile males being introduced into the wild. The females will be destroyed.
The costs associated with this experiment are somewhat of a closely guarded secret and Dr Wheeler was careful not to reveal these costs, but said that in his opinion, “It is extremely cost-effective and if successful, the cost benefit to the Cayman Islands both in terms of public health as well as the direct economic benefit in increased tourism more than justifies the experiment and its associated costs.”
Dr Wheeler also stressed that contrary to some public opinion, and in particular information that has emerged online following the outbreak of Zika which he says “is unsubstantiated hysteria”, the GM mosquitos do not represent a threat to human beings in anyway but in fact, “represent an environmentally friendly solution”.
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