Can mosquitoes transmit Aids?

Can mosquitoes transmit Aids? http://www.deccanherald.com/Content/Aug182007/living2007081719735.asp
Dr Chittaranjan Andrade

We live in a mosquito-infested part of the world, and even if all the experts reassure us, we want to know why mosquitoes cannot transmit Aids. So, consider three situations in which concerns arise.

In the first scenario, you are in a room with a bunch of people and a cloud of mosquitoes. It is dinnertime, and one of the mosquitoes sups on a gentleman who has Aids. The mosquito wobbles off in search of dessert and chances upon you. Now, without washing its mouth parts, it chooses to feast on your blood. You worry that its fangs are blood-stained; you remember that Aids can be spread through contaminated syringes; you panic: when that mosquito bites you after biting an Aids host, is it injecting Aids-containing blood into you?

In the second scenario, you have just been bitten by a mosquito. You wonder: has this mosquito fed on an Aids host recently? If yes, has the mosquito become a flying host to the Aids virus? Has the virus multiplied inside the mosquito and migrated to the insect's salivary glands? And, has the virus been transmitted to you in the mosquito's saliva during the course of the bite, just as happens with the classical mosquito-transmitted diseases?

In the third and what, to you, seems to be the worst-case scenario, the mosquito has gorged itself on an Aids-infected crowd of people. It can fly no longer and settles down on you to rest. You resent being treated as a landing zone; so, you swat at it. Hooray, for the first time that evening you manage to kill one of these pests. Alas, you are aghast to discover that there's Aids-blood splattered all over your skin in the very place that you have a cut. What are your chances of getting Aids?

Scientists have studied each of these scenarios with a variety of blood sucking insects and here, in a nutshell, are the reasons why mosquitoes do not transmit Aids. As an Aids-infected individual actually has very little Aids virus actively circulating in his bloodstream, estimates suggest that Aids transmission through contaminated mouth parts would require being bitten by ten million mosquitoes that have just fed on Aids-infected individuals.

So, the chances of this form of transmission are virtually nonexistent.

For the same reason, the chances are negligible that a mosquito will ingest sufficient Aids-virus particles in its tiny meal to transmit Aids even if the mosquito is killed directly over a cut on the skin immediately after feeding on an Aids-infected person.

Then, mosquitoes digest the virus that causes Aids. As the virus does not survive to reproduce and later migrate to the salivary glands, the mechanism that most mosquito-borne parasites use to get from one host to the next is not possible for the Aids virus.

Lastly, mosquitoes take in blood through one channel and inject saliva into you through another channel. This is different from the syringe and needle analogy wherein the same channel draws in and flushes out fluids. So, if the mosquito bites you after feeding on an Aids host, it does not flush out Aids blood into your bloodstream. In other words, the syringe and needle analogy is not applicable to mosquitoes. So, although mosquitoes may transmit diseases such as malaria, they do not transmit Aids.