Engineered Mosquitoes Could Wipe Out Dengue Fever

Christina Valencia points us to a Wired story about scientists who plan to use genetically modified mosquitoes to reduce the population of Dengue-carrying insects. The altered genes cause newly born mosquitoes to die before they are able to breed if they are not supplied with a crucial antibiotic. This is a more aggressive approach than the anti-Malaria work we discussed last year. From Wired: "Mosquitoes pass dengue fever to up to 100 million people each year, according to the Centers for Disease Control and Prevention. Up to 5 million die. If the scientists can replicate their results in real field conditions, their technology could kill half of the next generation of dengue mosquitoes, which scientists say would significantly reduce the spread of the disease. If all goes well the company envisions releasing the insects in Malaysia on a large scale in three years."

Comments

Are mosquitos important?

[rastoboy29]

I have often wondered (living in the mosquito-ridden South), if mosquitoes have any benefit to the ecosystem at all.  We often hear about how if you remove one creature from the ecosystem, the whole thing changes.  But mosquitoes?  I'm not sure they would be missed by any creature. 

Re:Are mosquitos important?

[MichaelSmith]

Bottom line is that Mosquito larvae are extremely beneficial to ecosystems (as food)

Back when my wife and I had just bought our house I installed two small ponds. Within days we were being bitten alive by mosquitoes. You could see the larvae swimming around in the ponds. We went down to the local creek and returned with a couple of dozen small fish. Within two days we had our result. Hardly any mozzies and fish twice the size.

Won't Work

[theshibboleth]

I don't really understand how the company can expect this approach to work. From the article:

Oxitec's technique is considered less controversial by some scientists because the genetically modified insects are programmed to die, not take over the existing mosquito population.

If the modified mosquitoes are to have any effect they must replace the wild mosquitoes. Otherwise, the wild mosquitoes will still continue to transmit dengue to humans. The article doesn't say whether offspring of wild and modified mosquito live long enough to breed nor what proportion of them still depend on tetracycline, but if you have two populations, one that dies young and another that doesn't and is thus able to breed longer, the longer-lived population will outcompete the short-lived one. Thus if the goal of this is replacement, that too would not work. At best they could hope to kill off maybe half of the mosquito population and thereby reduce dengue fever in the short-term, but doing so could unbalance the ecosystem and potentially have negative effects, including disease, for humans. Maybe a better approach would be to create mosquitoes that only die if they are infected with dengue fever.

Re:Won't Work

[Big Bob the Finder]

Just a stab in the dark, as I don't really have any special insight here. But it would seem likely the concept is to breed large quantities of GMO'd mosquitoes in the lab (providing them with the antibiotic throughout their life cycle), and then release them into the wild. They would then mate with wild-type skeeters, producing offspring with the gene. When those offspring fail to reach maturity because of the absence of tetracycline, it reduces the number of mosquitoes in the wild.

This is not exactly a new concept, although the implementation is quite different. Cattle screw worm (which was a serious economic pest) has been eliminated from North and South America from an aggressive irradiation program in which larvae are reared in large numbers, and then irradiated with cobalt-60. Insert your own "huge, radioactive flies" joke here, but the net upshot is that the irradiated flies mated with irradiated flies and failed to produce fertile offspring for whatever reason. Fewer fertile offspring is a good thing when it comes to population control of undesirable cattle parasites.

Similar programs with Mediterranean fruit flies have been used to control or eradicate populations, but there were some issues a few years back with making sure they really were sterilized by the procedure.

So, it's nothing *that* new, and variations on the technique have proven useful in the past. Now instead of green, glow-in-the-dark flies, we'll just have mutant, GMO'd mosquitoes. Life goes on- hopefully without dengue. Maybe someday without malaria.

flying needles

[tonyahn]

what will they come up with next? Maybe they can genetically alter the mosquitos to carry our flu shots.

The Eco-Nut replies are telling

[ZWithaPGGB]

Lots of people worried about birds or "The Ecosystem". Very few seem to be worried about the millions of PEOPLE who die HORRIBLE DEATHS thanks to Dengue fever.

I guess it's to be expected from the "Silent Spring" crowd, who refuse to acknowledge that the REAL effect of banning DDT has been millions of deaths from malaria, against a hypothetical doomsday scenario. Sound familiar?

Re:Ripple Effect

[Dutch Gun]

I'm fairly certain that if someone you cared deeply for was at serious risk of catching Dengue, you really wouldn't give care quite as much how the ecology would fare without those mosquitoes.

Oh, and take a walk out in a tropical region sometime. You'll quickly realize that the notion of the eco-chain being in any significant peril because one species of insect disappears is a bit far-fetched, I think. The number of insects (both in general number as well as the number of species) is pretty staggering. Species have disappeared all throughout history, and nature is fabulous at filling available niches.

I'd have no hesitation in pulling the trigger if it mean eliminating every damn mosquito on earth. Sorry if that sounds unenlightened.

Re:Didn't we learn

[Rei]

Seriously, it won't work unless its done every year

Well, there's an easy solution for that. Genetically engineer them to make them go extinct.

This article on Slashdot is proposing something a *lot* more tame than the specicide proposal. Basically, most genes have a 50% chance of passing on to offspring, but certain "selfish" genes game the system and all but guarantee that they're passed along. So, you make a selfish, lethal, recessive gene -- that is, a mosquito can have one copy and survive just fine. When it mates with a wild mosquito, it'll produce offspring that almost all have the recessive, lethal gene. This will continue until most of the wild population now has the gene -- and then they all start dying off. They can no longer interbreed.

Because it sweeps through so fast, there's no chance to adapt resistance. The only thing that can save the species is isolated pockets that manage not to interbreed with the outside world, then escape after all of the others are dead. Hence, effective, widespread distribution of the engineered individuals is critical for complete specicide. As for side-effects, not only has localized extinction of the Anopheles mosquito not had any adverse impact on the ecosystem (other insects fill in the gap on the food chain), but current control attempts are not mosquito-specific; they kill *many* species in large numbers, and we do it every year.