For as long as I can remember, they have come for me. They follow me everywhere, stealing a tiny drop of my life force and replacing it with poison before I even know they’ve been there. I still bear the scars of their attacks on my legs and ankles. I have tried every defense– chemical, physical, electrical…
And still, the mosquitos come.
There are some of you who may think I am being a tad dramatic. They aren’t so bad, you think. And still, there are those of you who know exactly how I feel. While your friends are free to enjoy the warm weather and backyard barbecues you are stuck inside or doused in deet (or both!), scratching and picking at your wounds and thinking why me! Your friends can light all the citronella candles they want, but you know the truth: they are still out there. And they are coming for YOU.
What makes some of us more susceptible to mosquito bites than others? Were we born under some unlucky star? Do our less susceptible counterparts have mosquito kryptonite running through their veins?
Maybe you remember from my previous post about drug-sniffing bees that insect antennae are the most sensitive biosensors in the natural world. With their antennae, insects can smell and even taste the faintest odors from several kilometers away. Mosquitos are particularly sensitive to chemical markers (odor molecules) that radiate from our skin, like glowing neon signs that advertise fresh blood ahead. But if these odor molecules are emitted by everyone, why are some of us covered in bites while others are bitten once or twice a season?
There are a number of factors that impact how you are perceived by these six-legged predators, but really it all boils down to what you smell like and how smelly your smell is. That is, what specific chemical markers you emit and how strongly you emit those markers.
Markers related to blood-type have been shown to influence mosquito bite preference. One study found that mosquitos are more likely to land on individuals with O blood-types than any other blood type! This means that the ‘smell’ of type O blood is especially tantalizing for the little blood-suckers (gives a whole new meaning to ‘universal blood donor’). Each blood type has a different combination of proteins and sugars that makes up the chemical marker mosquitos are sensing. Individuals with type A blood are the lucky ones with the least preferential landings. So if blood-type is the ‘what you smell like’ half of the equation, what about the ‘how smelly is your smell’ half?
Your secretor status is how strongly you secrete chemical markers about your blood type through your skin and saliva. If blood type is the color of your neon ‘Eat Me!’ sign, secretor status is how bright your sign glows. Individuals with a high secretor status glow much brighter than non-secretors and attract more mosquitos, regardless of their blood type. Only 15-20% of the population are non-secretors. High secretors with type O blood just happen to have the particular combination of genes that have us glowing like big bright buffet signs.
So do non-secretors just fly under the radar, totally undetected by the flying hoards of tiny bloodthirsty beasts? Not exactly. Another study found that pregnant women are more attractive to mosquitos than their non-pregnant counterparts. Now, I know what you’re thinking, a pregnant lady must smell like a two-for-one dinner special, but that isn’t quite how it works. Mosquitoes also use carbon-dioxide to find their meals, and pregnant women produce 21% more carbon-dioxide when they breathe. Pregnant women are also warmer than non-pregnant women, and the extra body heat increases the release of other chemical signatures that help mosquitoes find their hosts.
The factors that make us more susceptible to mosquito bites also make us more susceptible to disease. Mosquitos transmit a number of diseases including malaria, Zika virus, dengue fever, and West Nile Virus. These blood-sucking devils claim more human lives than any other creature on the planet. Still think they aren’t so bad? Scariest of all is that our susceptibility to life-threatening disease is largely out of our control. What we CAN do is continue learning about mosquito bite preferences so we can find more effective ways to defend ourselves. For now, I’ll hide indoors with my can of bug spray, sleeping with one eye open.
Michelle Ziadie is a Ph.D. student in the Department of Genetics at UGA working on the evolution of maternal effects and undergraduate evolution education. A native of Miami, Florida with Caribbean roots, Michelle never turns down an opportunity to engage with spicy food or spicy music. When she’s not dancing the night away with friends or getting lost in the Georgia wilderness, Michelle can be found sipping a café Cubano and watching Teenage Mutant Ninja Turtles with her kitten, Thomas. She currently serves as an Associate Editor for the Athens Science Observer. More from Michelle Ziadie..