QotW: Do mosquitoes prefer blood group O?

And how would they know your blood group anyway?
19 November 2019





Vinnie - I have read mosquitoes have a preference of blood type, and prefer people with type O blood, over those with type B. Is this true? And how do they know the difference between types?


Phil - Now to finish. Question of the week and this week, Adam has taken a bite out of this question from Vinnie.

Adam - Are you one of those people that mosquitos are just drawn to? Or like me, are you lucky enough that you get to be smug that mosquitos will only come to you as a last resort? Could your blood have something to do with that. I reached out to Immo Hansen, from New Mexico State University to find out.

Immo - There is one study from 2004 on the landing preference of Asian Tiger mosquitoes on people with different blood types. Shirai and coworkers found that this species of mosquitoes prefers to land on subjects that had blood group O compared with subjects of all other blood types.

Adam - Uh-Oh then, for people with O blood types. But how can a blood type impact what’s going on?

Immo - Blood types are defined by specific carbohydrates, or sugars, that are on the surface of red blood cells. When they applied these sugar antigens to the forearms of test subjects, they found that subjects treated with the H antigen attracted more mosquitoes than subjects treated with antigens of all other blood types.

Adam - These antigens are also the reason that people with A type blood can’t take from people with B type blood. The H antigen is found on all blood types, so if you only have that, you’ve type O blood, and can give to everyone, especially mosquitos apparently!

Immo - With this study the scientists confirmed an earlier study from 1972 performed by Wood and coworkers that shows that blood type O is more attractive than B, which is more attractive than AB, which is more attractive than A. A recent study from 2019 from Prasadini and coworkers, shows that yellow fever mosquitoes also prefer blood type O, if they can choose between the four different blood types in and artificial feeding system. The big question, however is how mosquitoes can distinguish between subjects with different blood types, since host blood is usually not directly exposed to the air. Mosquitoes find their hosts using their sense of smell. So there must be some differences in the olfactory cues that subjects with different blood types excrete but those are still unknown.

Adam - And it’s worth mentioning that blood type isn’t the only factor, there’s loads of chemicals in sweat!As flummoxxed points out on the forum, being pregnant, and even a few beers can change how mosquitos respond to you. Thanks to Immo for flying in with an answer. Next time we’re tackling this one, from Geoff.

Geoff - How is it that there are rising sea levels impacting some island nations such as the Maldives and Kiribati, yet 1000 kilometres in any direction there is no discernible sea level change at all?


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