Monday, October 31, 2011

Fighting Dengue Fever with Engineered Mosquitoes: Good News or Otherwise?

Today’s online New York Times carries a story about a new way to fight dengue fever, a tropical disease that afflicts an estimated 50 to 100 million people annually and kills about 25,000 people a year. The disease is carried by a single species of mosquito, so if you can reduce or eliminate that mosquito, you also reduce the risk of dengue fever. Historically, spraying noxious pesticides was the only way to kill mosquitoes over large regions, but a British firm called Oxitec has developed a clever way to decimate populations of Aedes aegypti, the species that carries the disease. They have used genetic engineering to create a line of mosquitoes that die before reaching adulthood unless they are fed a particular chemical (specifically, tetracycline, an antibiotic). So to spell doom to Aedes aegypti, Oxitec breeds thousands of these mosquitoes in captivity by feeding them tetracycline, then releases them into the wild. In order not to make the mosquito problem temporarily worse, only males (which do not bite humans) are released. These little genetic time-bomb males look just as attractive to the native females, but their progeny don’t get their tetracycline fix in the wild, and die out before they can spread dengue fever. Population simulations show that once a certain percentage of wild females mate with the modified males, the entire mosquito population should collapse in that region.

Dengue fever is a truly miserable disease, as you can tell from its informal name, “breakbone fever.” I have known several people who have had it, and although they didn’t endure the severe hemorrhagic form (which is often fatal), it was one of the worst experiences of their lives because of the nightmarish bone and joint pain. So anything reasonable that will keep people from getting this disease is welcome news in my book.

This blog is about engineering ethics, not media ethics, although I must say that the news article in which this work is reported emphasizes the possible hazards of the new development. For example, in selecting which mosquitoes to releas, it’s hard to tell male mosquitoes from female ones, at least if you aren’t a mosquito yourself, so inevitably a few biting females are always released with the males. And the Times reporter found an academic spokesperson who criticized some field tests as being inadequately reviewed and vetted with public notification, pointing out that the tests have been made in countries such as the Grand Cayman Islands which have relatively weak regulatory structures.

From what I can tell, however, the Oxitec people have followed all applicable protocols, and the first notification of their work to the scientific community was a peer-reviewed publication in Nature Biotechnology. In this they are following accepted scientific procedure rather than rushing out with a news conference in advance of peer review.

For various reasons, the phrase “genetically modified” has become a trigger for fear and opposition in Europe, especially, as well as other regions. There is no single word to describe the situation in which a technology is feared, not because it has ever led to any significant harm to the general public, but for other reasons. One cynical view holds that because genetically modified crops were first developed to a large extent in the U. S., they posed an economic threat to European farmers, who then mounted a scare campaign to induce public fear and obtain legal restrictions against the sale of such products. If this was the case, the farmers largely succeeded, and now the fear of genetically modified anything is one of the background assumptions of millions of people.

One thing that is hard for some engineers to learn is the fact that when millions of people, including potential customers or otherwise affected parties, hold a particular view about something even if the view cannot be logically or reasonably supported, one cannot simply ignore that view and pretend it doesn’t exist. This may be one reason that Oxitec chose to try out their mosquitoes in places where people generally have more important things to worry about than genetically modified insects. Most places where dengue fever is a problem are poor and have inferior healthcare systems, and illness can mean loss of a job (assuming one has a job to start with). So to people in sub-Saharan Africa or Papua New Guinea, a company that lets a few non-biting mosquitoes loose in order to reduce the chances of your getting dengue fever looks like a good deal.

No engineering can be carried out without money, and Oxitec is hoping that they can show enough good results for their process to be paid for by governments who see the doomed-mosquito trick to be more cost-effective than treating millions for the effects of dengue fever, or even worse, doing nothing. Obviously they have some challenges ahead of them, but it seems short-sighted to me to throw up roadblocks just because the whole idea of genetically modified critters is under a cloud in some places.

The best argument I can think of for opposing the general release of genetically modified mosquitoes is that there may be some sinister unintended consequence lurking in the background. But that’s why people do field tests: to uncover such problems and deal with them before they cause widespread harm. Here’s hoping that Oxitec does a good job of looking out for such problems, fixes them if they occur, and then goes on to alleviate the miseries of dengue fever for millions of people worldwide.

Sources: The New York Times article by Andrew Pollack on Oxitec’s effort appeared on Oct. 31, 2011 at I also referred to the Wikipedia article about dengue fever.

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