Mosquitos and HIV

Cecil's Columns/Staff Reports
1

From this URL, the second question:

http://www.straightdope.com/mailbag/mwestnile.html

Now, I think that they left out a crucial piece of information. With compliant mosquitos for West Nile, the virus makes its way into the mosquito’s own circulatory system, including its saliva glands. The saliva is the medium that transmits West Nile. How come HIV cannot make its way into a mosquito’s saliva glands? That, IMO, is the question.
The explanations offered were iffy:

  1. Not enough viruses - plausible, but surely there are instances where enough virus particles are picked up. This explanation cannot account for the complete lack of mosquito HIV transmition.
  2. The virus is food. I can understand a virus being digested in the stomach, but why is this the case for HIV, but not for Maleria or West Nile? Why isn’t HIV protected while these viruses are?
  3. The mosquito doesn’t squirt blood into a host. That’s fine, but that doesn’t stop it from passing on West Nile and Maleria. This last reason is lame, particularly when it accompanies the preceeding article about the mechanics of mosquitos passing West Nile.

Now, I thought that the West Nile section was written well, and kudos for that. But the HIV section could probably have been its own article.

2

The crucial distinction, I think, is evident in the Staff Report. Arboviruses (ones transmissible through mosquitos) survive the gut of the skeeter, migrate out of the gut, through the insect’s circulation and end up in the salivary glands. HIV can’t achieve that path. Notice that there are “multiple points of failure” in that path:
[ul]
1: Can HIV survive in the gut of a mosquito? From the report: “HIV …[is] digested within a fairly short time”.
2: Can HIV make it out of the gut and into the mosquito’s own circulation. The report says “HIV remains inert in the mosquito’s stomach…”
3: Can HIV reproduce enough in the mosquito so that an “infectious dose” virus particles are carried to the salivary glands? Again, the report says “… in contrast to arboviruses, which typically reproduce and migrate inside the mosquito”
[/ul]
Does that help?

This is only my interpretation of the Staff Report until lisa or some-one else shows up.

3

I also felt that the article adequately explained the HIV issue.

Thanks VERY much for the article! It readlly did help to defeat a small bit of the world’s ignorance (of which I have more than my share).

4

But how come HIV remains inert and doesn’t reproduce or survive the subject, when other viruses do make it through?

5

Because arboviruses have evolved specific anti-digestion properties.

6

And because arboviruses are capable of infecting mosquito cells. Most viruses are capable of attacking only one or two specific types of cells (as in, specific species and specific tissue type), and a virus cannot reproduce unless it infects cells.

7

Fair enough. I guess I was looking for the mechanics of it (HIV lacks a specific protien, or whatnot), but I accept the claim that mosquitos cannot pass it.
However, do we know that HIV is digested by mosquitos, or is it simply kept out of the mosquitos circulatory system?

8

The HIV virus is not an arbovirus; it will not survive a trip thru the mosquito digestive system. Nor a human digestive system, either.

That’s why blow jobs, even swallowing semen, is ‘safer’ than some other sexual activities. Any HIV virus that was swallowed will be killed by the digestive system.

It’s much more risky if you happen to have a cut or open sore in your mouth – that might allow HIV virus to come into direct contact with your bloodstream, which is much more of an infection risk.

9

Two points,

One, as as already been mentioned, the simple answer is that certain organisms and virii are adapted to survive the digestive systems of its host organisms and some are not.

Two, malaria is not caused by a virus, but by a protozoan parasite.

10

from the piece: ``Mosquitoes don’t regurgitate for feeding, unlike some of their more disgusting dipteran brethren.’’ I’m appalled at the implication that regurgitating dipterans are “disgusting.” On behalf of all regurgitating dipterans I demand an apology.

11

This isn’t at all significant for the overall article but it does read a little funny. From the second to last paragraph in the West Nile answer:

That’s a new one on me.

12

The author here - my apologies for not responding sooner, but I’ve been on the road. Thanks to all who have clarified the points. Just to reiterate: the lack of human T-cells (where HIV replicates) in mosquito stomachs and their fragility in a hostile environment filled with digestive enzymes make it highly unlikely for any HIV virus to survive long enough to migrate to the salivary glands. Mosquitoes are also unable to squirt blood back into a host once they take it up - what they squirt into people is saliva and that comes through a different set of “pipes” than those that take in blood. So bloodmeals travel in one direction.

Arboviruses have evolved to backtrack from the stomach to the circulatory system to the saliva glands of mosquitoes where they eventually end up in a vertebrate host. The tiny West Nile virus is able to infect the cells that line the mosquito’s gut. When these cells are filled with new viruses, they burst, allowing the viruses to leave the gut and enter the circulatory system. HIV has evolved to take a different replicatory route by binding to CD4 receptors found on human T-lymphocyte cells.

My apologies to all the vermiform dipterans and their spongy mouthparts.

Heh, that’s new on me too. My spell checker doesn’t find brain farts. Shirts, shirts!

Thanks again for all your comments!

lisa

13

[aside]
I survived my (imagined?) bout with WNV but I really miss our crows. :frowning:
[/aside]

[different aside]
This is my VERY FIRST POST in Comments on Staff Reports EVER!
[/different aside]

[something that actually has something to do with the topic]
Look at it this way: If mosquitos spread HIV 98% of humanity would be dead.
[/something that actually has something to do with the topic]

14

We’ll have the shorts changed to shirts. Thanks, Threadkiller.

And welcome to the Straight Dope Message Board CoSR forum … glad to have you with us.
[mutter]Over 6000 posts, and none of them here? harumph[/mutter]

15

Hey, Dex, once the Staff has had its way with a topic, what more is there to say? It’s not that you guys get slack with the facts or anything.

16

[quote]

from vodyanoi

Now, I think that they left out a crucial piece of information. With compliant mosquitos for West Nile, the virus makes its way into the mosquito’s own circulatory system, including its saliva glands. The saliva is the medium that transmits West Nile. How come HIV cannot make its way into a mosquito’s saliva glands? That, IMO, is the question.

[quote’/]

A basic question , please: Were the HIV you refer to actually observed in an electron micrograph?

All of the claims regarding the saliva and transmission of the West Nile are you asserting them as unconditional fact?

If not unconditional fact, what are the conditions that limit the integrity of the information as fact?

If not, what conditions do you place on the acceptanc elevel for a reader?

[quote]

The explanations offered were iffy:

  1. Not enough viruses - plausible, but surely there are instances where enough virus particles are picked up. This explanation cannot account for the complete lack of mosquito HIV transmition.

[quote/]

Can we assume from this statement that the assertion is sheer speculation?

Is there unambniguous scientific documentation in the fo rm of published papers that establish the existence of HIX+V as a fact,
anywher in the universe?

If so what are the documents?

[quote]

  1. The virus is food. I can understand a virus being digested in the stomach, but why is this the case for HIV, but not for Maleria or West Nile? Why isn’t HIV protected while these viruses are?
  2. The mosquito doesn’t squirt blood into a host. That’s fine, but that doesn’t stop it from passing on West Nile and Maleria. This last reason is lame, particularly when it accompanies the preceeding article about the mechanics of mosquitos passing West Nile.

[quote/]

Who prepared these three statements?

Were any government lagencies responsible for the formation of the report?.

If so which ones?

Are the statements above arrived at as a result any identifiable rersearch effort?

Are you just a messenger, or did you have any decicion level function regarding the inputt to this document?

[

[quote]

Now, I thought that the West Nile section was written well, and kudos for that. But the HIV section could probably have been its own article.

[quote/]

Is this statement concenred with literary aesthetics or is it directed at some technical aspect of HIV?

What scientific justification can you offer the reader for believing any part of the report?

What is your scientific , educational and professional experience that qualifies you to offer any fact or process that can be verified?

17

Dropzone

]

Me too, tell me where you get these facts that are offered so
casually?

18

I think you are being sarcastic. You could be in big trouble around here being like that.

19

Mhernan, I’m not sure exactly where you’re coming from.

If your questions are legitimate, then I think you’re working under a misapprehension. Neither Staff nor Cecil write science textbooks. Our material is intended to provide the overview answer, dispelling the ignorance to the degree that we think relevant for almost all of our readers. We do not try to provide the definitive, all-inclusive textbook on a topic. Anyone who wants further detail or further information is welcome to go and research for themselves.

If your questions are designed to make some sort of socratic political point, they don’t belong in this forum. If you want to argue that HIV doesn’t cause AIDS, or that mosquitos don’t exist, or that West Nile is a mental illness, please go to Great Debates. Not here.

If your statements are merely trying to be provocative, then that’s border-line trolling and being a jerk. If you want to stick around here, please watch your manners and tone. You may consider this a formal warning from an Administrator.