Genetically Modified Mosquitos Can Stop Dengue

I am going to write about how genetically modified organisms (GMOs) are potentially a solution for dengue. Dengue is a mosquito-borne infection characterized by very high fever and headaches followed by extreme weakness. The weakness is caused by a drop in the platelet count of the patient. In extreme cases the patient suffers internal bleeding (hemorrhaging) due to the thinning of their blood. Recovery is often associated with prolonged fatigue and depression, but in extreme cases dengue can be fatal. There is no known treatment or cure for dengue other than rest and careful hydration and nutrition. The incidence of dengue is increasing worldwide especially in Asia. The dengue mosquito AedesAegypti is a day time feeder, and has even become resistant to cooler climates in Europe and North America.

A British company called Oxitec, which was started in Oxford University, is using genetic engineering to find a solution for dengue. The male mosquitos are genetically modified so that their young die before they are able to reproduce. The young survive as larvae, but die before they mature. The field work carried out in the Cayman Islands in 2009 was successful and legitimate enough to be recognized by the World Health Organization (WHO). The genetic engineering uses a tetracycline-controlled transcriptional activator (tTA). The tTAcan be controlled to be ‘on’ or ‘off’ in the presence of antibiotic tetracycline in a way that can stop the mosquitos from producing other proteins needed for the mosquitos to survive.

The WHO estimates that there are over 2.5 billion people (40% of the world’s population) at risk of getting dengue. The number of reported cases has continued to increase to over 2 million in 2010. About a quarter of these required hospitalization, many of which are children. Since there is no treatment for dengue, the solutions must be based on prevention rather than cure. The genetically modified mosquitos are one of the most promising possibilities. In the Cayman Islands, the experiment with genetically modified mosquitos reduced the mosquito population by 80% in 3 months.

Critics are worried that if the genetically modified males are released into the wild, where the same antibiotic tetracycline (which is used in agriculture and the food industry) is found, then the males maybe able to breed successfully and their offspring will survive. Also, the genetically modified females may escape carrying the gene or protein, and since it is the females that bite and spread disease, this may be passed on to humans with toxic or allergenic effects. Probably the most immediate limitation is that the experiments have only been done on a relatively small scale to date, and so the challenges and consequences of a massive scale up are not known.

Based on the evidence presented above, the use ofgenetically modified mosquitos to solve the spread of dengue would appear to be a good thing. Dengue causes tremendous suffering and even death for huge numbers of people, many of them in developing countries and many of them children. Even North America and Europe are now at risk because the dengue mosquito has become resistant to cooler climates. However, there is a pressing ethical issue. It is not known with complete certainty what the consequences will be if huge numbers of genetically modified mosquitos are released into the wild. If the males are able to breed and their offspring survive, and the females bite carries toxic or allergenic effects, then the program may have the opposite effect to that intended. Is this a risk that is ethically acceptable?

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Ava Pilgrim