Posted: May 31, 2018

This is the 5th of eleven short news articles written by students, during the professional development class. This year we had the students interview their advisor(s), in an effort to help them better understand the larger context of their projects.

What happens when a mosquito gets sick?
By Mario Novelo

What happens when mosquitoes get infected with a virus like dengue? You might be wondering, "why in the world should we care about sick mosquitoes? They're annoying, and all they want is to feed on your blood and leave you with big itchy red bumps on your skin". If you ask Professor Beth McGraw she would tell you: "mosquitoes are the main contributors to infectious disease globally, particularly dengue fever". Dengue is a mosquito transmitted disease that represents a tremendous economic and health burden to more than half of the world's population.

The severity of dengue outbreaks not only depends on the presence of mosquitoes, but also on the type of dengue virus that is infecting them. There are 4 different types of dengue circulating around the world that can infect mosquitoes, and thus infect us. Each type of dengue virus might vary on how quickly it can render the mosquito infectious, ready to infect more humans.

This mosquito-virus interaction is what drew McGraw to wonder, what happens when a mosquito gets infected with each type of dengue virus, and what can we learn studying this process? She notes, "understanding how the different dengue viruses move through the mosquito's body, how quickly they get into the saliva and understanding how those traits vary across the population is really new territory, and it's really important because they inform our models of pathogen transmission to humans".

To study this puzzle, McGraw and her team use cutting edge methods, like gene sequencing, real time PCR and selective and large-scale mosquito breeding. With this, they have been able to shine a new light on dengue disease transmission. "There are some things that we are learning that are probably going against conventional wisdom. For example, most vector biologists would tell you that once a mosquito starts transmitting a virus, that it will do so for the rest of its life. Our work has shown that is not the case, that mosquitoes stop transmitting virus in middle to later ages. Another novel finding is that the window of time in which a mosquito starts transmitting the virus could be as early as 2 days post infection".

About the significance of these findings, McGraw mentions, "This research will improve our understanding of the epidemiology of dengue virus infections and inform vector control practices."

If we can understand how quickly each type of dengue virus gets into the saliva, we can design more accurate vector control strategies tailored to each dengue type. This way, we can design better transmission models that will eventually lead us to better public health policies.