Mosquitoes, Beer & Australia Day


This Saturday, 26 January 2013, is Australia Day, the official national day and commemorates the arrival of the First Fleet at Sydney Cove in 1788. For many Australians, it is all about BBQs, ferry races, cricket and the Hottest 100. To say beer drinking is common is probably an understatement. Do beer drinkers attract more mosquitoes? Could there be a more perfect story for our local media on the eve of Australia Day?

Besides rain, about the only thing that can spoil the day is a swarm of mosquitoes. Unfortunately, late January is at the peak of the local mosquito season. This year, Australia Day falls about two weeks after some major tidal flooding of our coastal wetlands (particularly the east coast of Australia). This is a major trigger for mosquito activity. This summer has already been marked by ideal conditions for our major nuisance-biting pest and vector of Ross River virus, Aedes vigilax (the saltmarsh mosquito). Current mosquito numbers along the NSW coast are the highest they’ve been this summer and local authorities have issued health warnings.

While the idea that beer drinkers attract more mosquitoes is a quirky story and is bound to spark some media interest, the phenomenon is more than just folklore. There have been a couple of studies looking at the role of alcohol in influencing the attraction of mosquitoes. A Japanese study published in the Journal of the American Mosquito Control Association  demonstrated that drinking 350ml of beer increased the landing rates of mosquitoes.

One of the most recent, and perhaps well publicised, studies was by Lefèvre et al. (2010) “Beer Consumption Increases Human Attractiveness to Malaria Mosquitoes”. In their study, Anopheles gambiae (probably one of the world’s most important malaria vector) were used in Y tube-olfactometer tests to see if their host-seeking behaviour changed in the presence of beer drinking and non-beer drinking volunteers. The results showed that 15 minutes after drinking 2 pints of beer (a little less than 3 schooners by Australian standards), beer drinking volunteers attracted more mosquitoes. The reason for this result was unclear but it wasn’t due to either a change in the temperature of the volunteers or increases in exhaled breath (two factors that are generally thought to increase an individual’s attractiveness to mosquitoes).

There have been many studies over the years that have demonstrated a difference in the attraction of mosquitoes in response to humans. It is a subject that fascinates many people and has lead to many urban myths about mosquito attraction and repellency. While the exact reason why some people attract more mosquitoes than others hasn’t quite been nailed down, it is thought to have something to do with the “smell” of the chemical cocktail of microbes on our skin. There are thought to be over 300 different chemicals on our skin and that their “blend” influences how many more mosquitoes we attract compared to our friends. It is possible that drinking beer changes that blend and, consequently, beer drinkers end up attracting more mosquitoes. In reality, based on recent studies, after a few beers you’ll probably not notice the mozzies and you’ll be a little less effective in swatting them away.

The key issue here though is to remember that not all mosquitoes share the same tastes for humans. Just because Anopheles gambiae is more attracted to beer drinkers, it doesn’t mean that the Australian saltmarsh mosquito will be too. The difference in host-seeking behaviour may be most vividly demonstrated in studies that showed that Anopheles gambiae was attracted to Limburger cheese. This smelly cheese contains bacteria closely related to bacteria found on our feet. While this has been shown to attract mosquitoes with a preference for biting humans, mosquitoes with broader preferences, such as Aedes vigilax, are less likely to be attracted to the stinky cheese.

What does all this mean for beer-drinkers on Australia Day? To be honest, you couldn’t be certain that drinking beer will result in more mosquitoes being attracted to you. However, there is little doubt that there will be plenty of mosquitoes about over the weekend and unless you take precautions to avoid mosquito bites, you’ll end up with a few extra itchy bites on your return to work or school and, at worst, increase the risk of catching a mosquito-borne virus such as Ross River virus. You can find some tips on avoiding mosquitoes here.