Mozzies get under my skin

Regular readers might remember that I’m quite fascinated by mosquitoes. That’s mainly because I’m one of those people mosquitoes are really attracted to.

I’m basically everyone else’s mozzie repellent. Whenever I’m around, any mozzies in the vicinity seem to ignore everyone else and feast on me.

I wouldn’t mind if they didn’t leave me so swollen and itchy. After all, the mozzies are only trying to get a blood meal so they can lay their eggs.

If they don’t feed, their eggs won’t mature. And despite how I feel about mozzies, the larvae are a source of food for fish, and the adults help pollinate plants.

I’m fascinated to know what makes me so attractive to mozzies. Last year, a study suggested it might be my blood type. Now, a new study points the finger at the microbes living on my skin.

Back in late 2017, Dr Ellen De Obaldia, Professor Leslie Vosshall and their colleagues started to test people to see how attractive they were to mozzies. They made a piece of kit that has a large chamber with two smaller chambers leading off it.

Off each of the small chambers is a trap to stop the mozzies flying any further. After each trap is another chamber where the researchers put the ‘‘stimulus’’: either someone’s forearm, or a piece of nylon they’ve worn on their arm.

A mixture of air and carbon dioxide gets blown over each stimulus, picking up any smells and pushing them downwind to the big chamber, where all the mozzies are buzzing around. If either of the two options takes their fancy, the mozzies will fly upwind towards it and be counted as they enter each smaller chamber.

Doing this, the researchers were able to split people into high attractors (mozzie magnets), intermediate attractors, and low attractors (mozzie repellents). Then they used a technique called gas chromatography mass spectrometry to identify any compounds on the nylons worn by each subject.

After testing more than 60 people, they found that their mozzie magnets produced significantly higher levels of three carboxylic acids – pentadecanoic, heptadecanoic and nonadecanoic acids – as well as another 10 similar compounds they couldn’t identify.

Previous studies have shown that the bacteria that live on us – our microbiome – contribute to the compounds found on our skin. The bacteria can make compounds themselves or make enzymes that break down the oily substances our skin secretes. What this latest study shows is that our skin microbiome probably contributes to what makes us attractive – or not – to mozzies.

While this study didn’t find a way to make me less of a mozzie magnet, there’s a way we can help Te Papa’s experts understand which mosquito species are present in New Zealand and where they each live.

Yes, it’s a mozzie census! Dr Julia Kasper and her team need unsquashed mozzies from wherever people can find them around the country.

Head to Te Papa’s website for instructions on how to gently catch a mozzie, freeze it, and send it to them for identification.

Dr Siouxsie Wiles MNZM is an awardwinning microbiologist and science communicator based in Auckland.