November 11, 2004
Heart of American Radio
KGO Radio, San Francisco
Monster Mosquitoes
XM Satellite Radio: 9/11/05
The Osgood File (CBS Radio Network): 11/17/04, 3/18/05
KGO-TV (San Francisco): 11/26/04
Heart of America Radio reports on a scientist's work to eradicate malaria using a genetically modified mosquito.
Scientists at UC Davis are hoping to eradicate malaria by developing a genetically modified mosquito that cannot transmit the disease. Malaria has long plagued the populations of South America, Africa, India, and Asia, where mosquito bites infect up to 500 million people a year with this serious and sometimes fatal parasitic blood disease, according to the CDC. For generations, scientists have been trying to eradicate malaria by developing new drugs, researching possible vaccines, and using pesticides to wipe out local mosquito populations. But these measures aren't working – and some scientists, like Greg Lanzaro, a population geneticist at UC Davis, say that because of drug resistance and population changes, malaria is actually more prevalent now than it was 20 years ago. Instead, Lanzaro says he has a better way to stop the spread of malaria: genetically modifying mosquitoes so they are unable to carry the disease.
Lanzaro and his colleagues are planning a multi-year project to produce malaria-resistant mosquitoes – and he thinks they can do it within five years. "There's encouragement from the standpoint that we can get foreign genes into mosquitoes and they go where they're supposed to go," Lanzaro says, pointing out that scientists have already succeeded in genetically engineering mosquitoes that cannot transmit malaria to birds and mice. And, he says, scientists are quickly making progress on genes that block transmission of the disease to humans as well, by preventing the human malaria microbe from getting into the mosquito's saliva and thus entering a human's bloodstream.
The most difficult part scientifically, Lanzaro says, is figuring out how to get the lab-engineered mosquitoes to spread their genes into natural populations. After all, he points out, it's useless to engineer mosquitoes in the lab that can't transmit malaria when there are millions out in the wild that can. To solve this problem, Lanzaro wants to use a mobile piece of DNA called a transposon, which is like a controllable virus that scientists use to infect and insert genes into an animal. The idea, Lanzaro says, is for scientists to load up a transposon with the malaria-resistant gene in the lab, and then, using a tiny syringe, insert it into a group of mosquito embryos. The transposons would then integrate the malaria-resistant gene directly into the mosquitoes’ DNA, making it impossible for those mosquitoes to transmit the parasite that causes malaria. In this way, says Lanzaro, a small group of lab-raised mosquitoes could be released into the wild, and by interbreeding with wild mosquitoes, eventually transmit the beneficial gene to the entire population.
Michael Fernandez, a molecular biologist and director of science at the Pew Initiative on Food and Biotechnology, says that getting rid of malaria is a great idea, but genetically modifying mosquitoes and releasing them into the wild in order to do it could be a catastrophe waiting to happen. That's because releasing mosquitoes is much different than planting genetically modified crops like corn and soybeans, which are routinely harvested in the US. Fernandez says that there are safeguards in place to control these genetically modified plants. For example, many varieties are engineered to be sterile so they can’t cross-pollinate, and there aren't any native varieties of corn and soybeans in the US anyway for genetically modified crops to infect. Even with these safeguards, there is still some public opposition.
But there are no such safeguards for mosquitoes. "Here you are talking about trying to introduce a set of genes into that population that you want to be established in there permanently," Fernandez says. That's dangerous, he says, because if any unforeseen problems arise, they will be very difficult, if not impossible to reverse. And potential problems are numerous, says Fernandez. First, there's a risk that transposons could "jump around and activate other genes" in the mosquito. These pieces of DNA are somewhat unpredictable, he says, and there's a chance that they could pick up and pass on another gene besides the anti-malarial genes. In a worst-case scenario, the mosquitoes could pick up genes for fast flight or a longer lifespan and begin transmitting that to other mosquitoes, thus creating mosquitoes that are even harder to kill.
There's even a chance that transposons could infect other insects, Fernandez says. In rare cases, "you can get a jumping of genes across species," Fernandez says, either when genes piggyback on viruses that are transmitted between animals or when transposons move from species to species in a little-understood process known as horizontal gene transfer. In either case, though, mosquitoes could end up passing their genes on to beetles, flies – or even humans, although he says the risk is pretty small. Still, the bottom line, says Fernandez, is that "we're never very good at predicting broad-level ecosystem things and we just don't know a lot about what can happen when genetically modified insects are released into the wild."
That argument isn't good enough for Lanzaro. Releasing mosquitoes is a complex issue and there are risks, he acknowledges. But, he says, the kinds of risks Fernandez talking about are very unlikely, and by working with governments and regulatory systems, Lanzaro says scientists can minimize danger even further. Furthermore, Lanzaro says, the risks are worth the potential benefit of curing malaria. "The idea of doing this can’t be dismissed as easily as we might dismiss producing a genetically modified tomato with longer shelf life – there is more at stake here," he says, pointing to statistics showing that two-to-three million children every year die from malaria. "Weighing the risk and benefit is a little bit different," says Lanzaro – and he's willing to take the risk, even if it means unforeseen changes in our ecosystems. So Lanzaro is pushing ahead with his proposal to develop genetically modified mosquitoes. His team is negotiating with the nation of São Tome.
Contact:
Kathy Keatley Garvey
Communications
UC Mosquito Research Program
Department of Entomology
396 Briggs Hall
University of California, Davis
Davis, CA 95616
Phone: (530) 754-6894
E-mail: kegarvey@ucdavis.edu
