Zika Virus and Why We Can’t Kill All of The Mosquitoes

Since news of the Zika virus outbreak first started spreading all over the internet, I knew that I was going to have to write a post. First because vector-borne viruses are MY thing and second because I KNEW this was going to be a big deal. But, I was still searching for the right angle. Yes I wanted to give the important info and talk a little bit about the virology behind it but what would make my post different from the majority of information already out there. Then yesterday I saw scientists, epidemiologists etc. calling for the full blown extermination of mosquitoes and it hit me. Whenever we learn about a new vector-borne pathogen that affects human lives, we always call for the extermination of the vector as if this has no other repercussions ecologically. This is never a good idea. Hold on, let me start from the beginning…

Zika Virus (ZIKV) is a positive sense, single stranded, enveloped RNA virus. It belongs in the same family of viruses as West Nile virus, dengue virus, and yellow fever virus, Flaviviridae. Like the others, ZIKV is transmitted via mosquito vector, specifically Aedes aegypti, commonly known as the tiger mosquito. ZIKV has been around for since the 1950’s. Cases of ZIKV are usually found in African and Asian countries along the equitorial belt. In 2014 the virus spread eastward toward the Pacific Ocean reaching French Polynesia, Easter Island and then reached the South and Central Americas in addition to the Caribbean causing a Pandemic in 2015 that is still growing in 2016.

Image: Flavivirus genome

Image: An Aedes aegypti mosquito

The most common symptoms of ZIKV infection include fever, rash, joint pain and conjunctivitis. Less common symptoms can include muscle pain. These symptoms can last from several days up to several weeks. The reason why ZIKV is so concerning now despite it being arounf since the 1950’s is that it has been linked to cases of microcephaly (small heads) in newborn babies whose mothers became infected during pregnancy. Now the CDC has issues travel guidance’s and warnings to those traveling to countries where cases of ZIKV have been recorded. Certain countries are advising that women delay getting pregnant until more research can be done about the viruses link to microcephaly in newborns. (This has HUGE implications for some of these countries that do not have access to birth control. More on that here.

From a general public health perspective one might think that this is just another nasty bug carried by mosquitoes. People have argued that wiping mosquitoes off the face of the earth would really be our best bet in reducing the burden of disease caused by vector-borne disease. In theory, this sounds like a reasonable idea. Get rid of the thing causing problems. Mosquitoes are the WORST, so its the perfect reason to wipe them out, right? However, anytime something sounds too easy, it probably is. We as humans have probably been making this mistake for as long as we have been in existence.

Mosquitoes are HUGE part of the ecosystem in many places. Adult mosquitoes are consumed by birds, bats, reptiles and other insects. The larvae are often consumed by fish and insects. While mosquitoes don’t make up an entire diet of any animal that we know of, they represent a huge amount of biomass globally and removing them from the ecosystem could cause some major breakdowns in the food chain of many animals, including humans. This is why One Health science is SO important. A lot of time we get so narrowly focused on solutions that we do not think about the repercussions they have outside of whatever problem we are trying to solve. Yes we might be able to get rid of a lot of vector-borne disease by killing all of the mosquitoes, but what are we going to do when ecosystems start to breakdown? Its just not sound science.

 Image: Example of a food chain that hinges on mosquitoes

Even if we did decide there were no issues with killing them, how exactly would we do that? Mosquitoes can lay there eggs in the tiniest pools of water. So anywhere there is litter or pollution and rain there are probably mosquito eggs. We have to clean up all of the pollution all over the world! (Hmmm, on second thought yes lets kill all the mosquitoes. Lets start cleaning up after ourselves!) We could spray pesticides everywhere but that would effect more than just mosquitoes, which would mean a loss of even more biomass and the destruction of even more ecosystems. (Does this still sound like a good idea?) It’s not an easy task at all.

A more eco-friendly approach would be to make sure there is no standing water in and around your home, that your window screens are intact, that you wear insect repellent (there are citronella based repellents for those concerned about deet), use bed nets and limit your time outside if possible, especially when pregnant. Another idea could be making your backyard mosquito predator friendly. These situations can be tricky to navigate and can also be scary. It’s best not to loose our heads those and put the resources we do have towards reasonable and reachable solutions.