Contributed by Guest Blogger: E. Doyle ’14
In order to disseminate successfully, viruses, being immobile, must adapt and evolve to utilize their surroundings to effectively propagate. One group of viruses that’s done this particularly well are the Flaviviruses, which are transmitted to humans via bites by infected mosquitoes. Though beneficial for the spread of the virus, Flaviviruses such as yellow fever, dengue fever, and West Nile virus cause a significant amount of serious and painful illnesses and even death in human beings. Of particular concern are the dengue fever outbreaks that have, according to the CDC, recently been common in many parts of the world. Since there is no cure for this virus, prevention is the only way to stop the spread. Scientists are currently looking to do this by controlling the mosquito population.
In a recent study, scientists considered two known methods of mosquito population control (sterilization of male mosquitoes, and genetic alteration of male mosquitoes that would cause them to be genetically programmed to die, as well as any offspring they produced) and mathematically projected how these methods would be most effectively utilized. The variable in this experiment was the frequency of the release of the mosquitoes altered by these two techniques. Would fewer mosquitoes be produced if these altered males were released frequently in small bursts, or less frequently in larger numbers? The projected effectiveness of the different timelines was shown by the calculated number of mosquitoes present in the environment afterwards, keeping in mind the as well as the mating competitive ability of mosquitoes that have been altered to control their reproductive success. If the altered males are able to mate as successfully as the wild type males are and lower the population of mosquitoes below a certain level, the virus will no longer successfully transmit.
Though genetically altered or sterilized male mosquitoes may often lose out when it comes to reproductive success, as has been shown in other real-life experiments, the numbers showed that the release of these mosquitoes into the environment still works when they are released very frequently rather than at lower frequencies. It should be kept in mind, however, that releasing these mosquitoes more frequently also results in higher costs. Also, since the results of these experiments were merely projected using mathematical analysis, it begs the question of whether the anticipated results of frequent mosquito release would be as successful in real life as they are on the page.
I think it’s a good idea to prevent dengue fever via mosquito population control. Though there are so many options to choose from when it comes to repel mosquitoes, this way is the best yet safest way to prevent diseases such as dengue fever.
I would be concerned about the unintended ecological effects of such a release. Would the genetically altered mosquitoes produce offspring that would die later in life, or as larvae? How would a reduced mosquito population affect success of other organisms? Perhaps the virus would spread from dead mosquitoes into other populations.
Also, it seems unlikely that this would be successful in real life, because the virus would continue to spread in mosquitoes that do not incorporate the altered genome into their subpopulation. Since altered mosquito populations will die anyway, this method does not directly address the problem, just causes a temporary drop in the mosquito population.
It’s interesting to see the problem of the disease being addressed through the carrier rather than vaccinations, etc. The approach of using genetic engineering and sterilization as a means of population seems like a very innovative approach to population control, not least because it avoids the collateral damage caused by insecticides. It makes me wonder if it would be possible to genetically engineer mosquitoes to have immune systems capable of removing the dengue virus from their bodies. Would there be evolutionary benefits to mosquitoes who did not carry the virus? If so, this would make genetically modifying them in this way quite effective, since the immune genotype would eventually become dominant.
It’s always cool to see how far mathematical projections can be taken, and they’re usually fairly accurate in their calculations. In this case, I don’t see why they shouldn’t go ahead with this plan; even though they might not find the optimal release rate immediately, I don’t see a downside to starting the release sooner, except for cost I suppose. But their data would benefit greatly from the real-world scenario and would probably give them insight into how to optimally release the mosquitos – a much better estimate than they would get with theorizing alone. It’ll be interesting to see how this works out; I hope it goes very well!