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Shooting The Magic Bullet

Lab mosquitos may block malaria transmission, but who decides when to release them?

By Matthew S. Meisel

New mosquitoes may block malaria transmission, but who decides when to release them into the wild?

The United States has much to be thankful for—amber waves of grain, lots and lots of freedom, and football. But one thing that doesn’t usually make the list of reasons-why-I’m-glad-to-be-an-American is malaria, or, rather, the lack thereof. With the exception of a small handful of rare cases, the U.S. is mercifully free of the disease.

Many tropical nations, especially those in sub-Saharan Africa, are not so lucky. Malaria is caused by a bacterial parasite which is spread by mosquitoes. Each year over 300 million people contract the disease. The Centers for Disease Control and Prevention estimates that 1 to 3 million people die from malaria each year, and three-quarters of the fatalities are African children.

Much progress has been made in controlling the disease—it was eradicated from the U.S. shortly after World War II. But three major factors, according to microbiologist Marcelo Jacobs-Lorena, have hindered eradication efforts in many regions: drug-resistant parasites, pesticide-resistant mosquitoes, and the lack of a malaria vaccine.

Jacobs-Lorena and his colleagues at Johns Hopkins University have taken a different approach to combating malaria. They have engineered a mosquito that produces an extra protein in its gut, which blocks the malarial parasite from infecting it. The team recently discovered unexpectedly that one of their engineered mosquito strains is “fitter” than ordinary mosquitoes. Once you infect it with a certain strain of mouse-borne malaria parasite, it lives longer and produces more offspring than infected wild-type mosquitoes. Place equal numbers of the two types of mosquitoes into the same cage, let the birds and the bees do their thing for a few generations, and the bioengineered insects take over, accounting for 70 percent of the mosquito population.

What would happen if these newfangled mosquitoes were released into the wild? The hope is that the modified mosquitoes would out-compete the existing ones, and the bulk of the mosquito population would be malaria resistant, thus preventing new human malaria infections. It’s not beyond the realm of possibilities that the engineered mosquitoes could entirely replace the wild ones. This solution would be simple and inexpensive. It would not rely on vaccinating entire human populations nor spraying pesticides to control mosquitoes. It would use mosquitoes to fight mosquitoes.

It’s a compelling bit of research.

In reality, the technology isn’t nearly ready to take flight. The mosquito species that Jacobs-Lorena used is not the most harmful of mosquito species and the parasite used does not infect humans. Furthermore, the modified mosquitoes only have an evolutionary advantage over infected mosquitoes, and in the wild only a small fraction of mosquitoes are infected with malaria.

But let’s optimistically suppose that these technological problems have been solved. A larger question looms: Should humans willfully change the genetic makeup of an entire species?

This is not meant as a moral question, although some would have moral qualms with this technology. Mosquitoes, one might argue, are a product of nature (or a deity) and ought not to be altered for humans’ benefit. Thankfully, few subscribe to this argument. Saving millions of human lives each year is a far higher priority than preserving the integrity of the mosquito genome out of respect for the genome itself.

The more important question is a scientific one. We need to ask if adding a new gene to every mosquito on the planet will have negative consequences that outweigh the decreased transmission of malaria. The short answer is that we don’t know—we need more research and larger-scale experiments—though we do have a little experience in wholesale genetic modifcations.

Humans have been overhauling some species’ genetic compositions—far more substantially than the dinky addition of a gene or two—since the beginning of civilization. Every year, farmers select the most bountiful individual plants and animals and breed their offspring to produce the next generation. Modern grain and livestock species look nothing like their ancestors from 10,000 years ago.

In agriculture, the effects have been largely positive: vastly increased food supplies. But the effects of modified insects are largely unknown. Would insect predators be affected? Would the mosquitoes better transmit other illnesses? More research is needed, but some effects might not be known unless the mosquitoes are actually allowed to breed in the wild.

But a more important question remains: Who gets to make a decision about whether mosquitoes should be released? It should not be the decision of the just the particular scientist; it should be a joint decision. Mosquitoes will cross national borders, so decisions should include a wide range of participants. We will need an international panel of scientists, policy makers, and perhaps ethicists to weigh evidence on this issue. That body (or a framework for assembling such a body) should be established now, so that if a better technology becomes available, no time is wasted in gathering the right people. I imagine, and hope, that a group like this will be able to determine that such a measure is safe.

Forming and operating such a body may be difficult—the U.S. Food and Drug Administration is evidence enough of how easily scientific decisions can become politicized. But it’s worth thinking about now. If a bigger, better malaria-resistant mosquito arrives next year, it would be a tragedy of epic proportions to spend years arguing about who should deliberate its release. We don’t yet have the magic malaria bullet, but we can think about human institutions in the mean time.



Matthew S. Meisel ’07 is a chemistry concentrator in Currier House. His column appears on alternate Fridays.

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