Sunday, February 12, 2012

Why can't mosquitoes transmit HIV?

In a recent survey of young Australians (18 to 29) 43 per cent believed they could get HIV from mosquito bites.

Although this is NOT the case, it does raise the question of exactly why not given that mosquitoes do vector a range of other diseases. I found this website at Rutgers that provides a very clear description of three possible mechanisms for transmission and then clearly describes why each one is simply not possible or is beyond the bounds of likely probablity. For example:

Many people think of mosquitoes as tiny, flying hypodermic syringes, and if hypodermic needles can successfully transmit HIV from one individual to another then mosquitoes ought to be able to do the same. We have already seen that HIV-infected individuals do not circulate enough virus particles to result in infection by contamination. However, even if HIV-positive individuals did circulate high levels of virus, mosquitoes could not transmit the virus by the methods that are employed in used syringes. Most people have heard that mosquitoes regurgitate saliva before they feed, but are unaware that the food canal and salivary canal are separate passageways in the mosquito. The mosquito's feeding apparatus is an extremely complicated structure that is totally unlike the crude single-bore syringe. Unlike a syringe, the mosquito delivers salivary fluid through one passage and draws blood up another. As a result, the food canal is not flushed out like a used needle, and blood flow is always unidirectional. The mechanics involved in mosquito feeding are totally unlike the mechanisms employed by the drug user's needles. In short, mosquitoes are not flying hypodermic needles and a mosquito that disgorges saliva into your body is not flushing out the remnants of its last blood meal.

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