From: ((Steven B. Harris))
Subject: Re: Insect transfer of AIDS
Date: 13 May 1995
Newsgroups: misc.health.aids

In <1995May12.233950.15409@lmpsbbs.comm.mot.com>
fergus@areaplg2.corp.mot.com (George Fergus) writes:

>Although I don't know of any suitable candidates, it is not impossible
>that some other biting insect could transmit HIV. Horseflies are
>responsible for transmission (among horses) of the lentivirus EIAV, an
>animal virus related to HIV.

   I didn't know that.  EIAV is a very close relative of HIV (it is the
virus which made Montagnier realize he had not a leukemia virus, but a
lentivirus, his LAV being antigenically gross reactive and visually
sometimes indistinguishable from EIAV).  If horseflies transmit EIAV
among horses, I would bet money they would be able to do so with HIV
between humans, at least in theory.  But see below....

>  But horseflies are "pool" feeders, so infected blood from
>the previous victim mixes with the blood of the current victim.
>Fortunately, people are seldom bitten by horseflies, and if a horsefly
>bit you, you'd know it.

  Indeed, I have been bitten by one in the Uinta mountains, and it is
MOST unpleasant.  Horses have to put up with it only because they have
no hands.  Humans nearly always get the *&%$ers before they have a
chance to do much feeding.  It would take not one but TWO really
disabled humans to transfer HIV this way.  You'd need not only an
unconscious PWA and a horsefly on one end, but something like a
quadruplegic or comatose victim on the other.

    Thanks for the interesting info.  Hmmm.  I'll bet horseflys also
transfer BLV (the bovine lentivirus which causes huge tumors) between
cows.

                                               Steve Harris, M.D.

From: sbharris@ix.netcom.com(Steven B. Harris)
Subject: Re: Why Mosquitoes Cannot Transmit the AIDS Virus
Date: 25 May 1997
Newsgroups: misc.health.aids

In <19970525011401.VAA09021@ladder01.news.aol.com> getwell@aol.com (Get
Well) writes:

>Why Mosquitoes Cannot Transmit the AIDS Virus
>
>Author: Jerome Goddard, PhD, Mississippi Department of Health; University
>of Mississippi School of Medicine
>
> Abstract: Public concern about the risk of HIV transmission from mosquito
>bites persists. However, research has shown that HIV does not survive or
>replicate in the arthropod vector, and arthropods are unable to transmit
>the virus from an infected host to an uninfected one. Additionally, an
>epidemiologic study found no relationship between HIV infection and
>exposure to mosquitoes. [Infect Med 14(5):353-354, 1997. © 1997 SCP
>Communications, Inc.]
[....]


>Within minutes of being fed blood contaminated with 5 x 104 TCID/mL of
>HIV, stable flies (Stomoxy calcitrans) regurgitated 0.2mcL of fluid
>containing ~ 10 TCID.[4] The minimum infective dose for humans
>contaminated in this manner is unknown, but under conditions such as those
>existing in tropical countries with large populations of biting insects
>and a high prevalence of HIV infection, transfer might theoretically be
>possible, although highly unlikely.



    I think I'd up the odds here a bit, knowing that the equine
infectious anemia virus (EIAV), a retrovirus quite closely related to
HIV, is INDEED transmitted from horse to horse via these stable flies
(horse flies-- the big nasty ones).   Since these critters also bite
people, I think it likely that a horsefly biting two people in a row,
with the first having AIDS, might very well transmit HIV in the manner
of EIAV.  No documentation of this every happening, but then again,
documentation would be hard to come by if it DID happen.  Absense of
evidence in this case is not evidence of absense.

                                         Steve Harris, M.D.

From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: sci.med,misc.health.aids
Subject: Re: question about HIV-infection
Date: 20 Apr 1998 08:22:34 GMT

In <353a7302.3032440@news.univie.ac.at> a9600024@unet.univie.ac.at
(Michael Schedl) writes:

>I have heard that mosquitos need to have their portion of blood only
>once a day and that it is impossible (?) for the virus  to survive in
>this case so that it can't be passed on to another host. But what if
>the mosquito is interrupted while sucking and has to look for another
>host and finds it within say 1-2 minutes? Is it possible to receive
>the HI-virus by being stung by a mosquito?
>
>I tried to find an answer and got hold of some brochures and they say
>it's impossible but I couldn't find a single line why. Could someone
>please give me a rational and scientific explanation why the HIV
>cannot be spread by mosquitos?
>
>Thanks in advance for taking the time to answer
>
>Michael Schedl
>Vienna, Austria
>(a9600024@unet.univie.ac.at)


Answer:

    Since mosquitos only suck blood in one direction, you'd have to get
your HIV from only the blood clinging to the outsides of the
mouthparts.  And that's not very much blood.  The virus is in such low
concentrations most of the time that people stuck with a medical needle
(a lot bigger than a mosquito's proboscus) have only a 1 in 500 chance
of getting enough blood to be infected.  That's because only about 0.01
cc of blood is transferred that way.

   It is theoretically possible to be infected by insects which are
more messy feeders, such as horseflies.  In fact, there's good indirect
evidence that this would work: the equine infectious anemia virus
(EIAV), which is a retrovirus and lentivirus like HIV, and which looks
very much like HIV (providing a first clue as to what HIV was when it
was first seen) is transmitted between horses by---- horseflies!   The
same horsefly should therefore be able to transmit HIV between people,
if it bit an infected and uninfected person in succession.  No case of
this has been documented, but then it would be hard to document, would
it not?  Basically, nobody really wants to talk about it.  The few
people who know about horseflies and EIAV (the lentivirus that is like
HIV in horses) haven't really wanted to scare people, I suppose.  Or
haven't thought about it.

                                     Steve Harris, M.D.

From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: sci.med
Subject: Re: question about HIV-infection
Date: 10 Oct 1998 09:55:16 GMT

In <35477b7e.8084555@news.global.co.za> gkay@hotmail.com (Grant Kay)
writes:


>On Sun, 19 Apr 1998 21:56:19 GMT, a9600024@unet.univie.ac.at (Michael
>Schedl) wrote:
>
>>I know this might appear ridiculous or even insulting to some people
>>but it's a serious question and I don't mean to offend you or waste
>>your time:
>>
>>On TV I've heard of a group of prison inmates who after having used
>>the same needle of a hypodermic syringe were HIV-positive. They all
>>said that their infection was due to the use of this one needle. I
>>don't know if they're lying (maybe they contracted the infection due
>>to some other reason like sexual contact with each other, ...) but let
>>us assume they are telling the truth.
>>
>>So a friend and I had a discussion about this and we were wondering
>>why someone could become HIV-positive by sharing a needle and not by
>>being stung by a mosquito soon after it has sucked the blood of an
>>HIV-positive person.
>>
>>I have heard that mosquitos need to have their portion of blood only
>>once a day and that it is impossible (?) for the virus  to survive in
>>this case so that it can't be passed on to another host. But what if
>>the mosquito is interrupted while sucking and has to look for another
>>host and finds it within say 1-2 minutes? Is it possible to receive
>>the HI-virus by being stung by a mosquito?
>>
>>I tried to find an answer and got hold of some brochures and they say
>>it's impossible but I couldn't find a single line why. Could someone
>>please give me a rational and scientific explanation why the HIV
>>cannot be spread by mosquitos?
>>
>>Thanks in advance for taking the time to answer
>>
>>Michael Schedl
>>Vienna, Austria
>>(a9600024@unet.univie.ac.at)
>
>
>According to my Pathology lecturer, the body temperature of the
>mosquito is too low for the survival of HIV.  This is why it cannot be
>transmitted this way.
>
>The reason HIV is transmitted through sharing of needles is the virus
>does live for a short period outside the human host (Not longer than
>30 seconds).  Not enough time is allowed for the virus to "die",
>before the next person uses the needle.
>
>Regards
>Jonathan Kay
>Johannesburg, South Africa



   It's more complicated than that.  The virus may "live" (retain
activity) for hours on surfaces, so that's not a problem.  The body
temperature thing is simply wrong, as the lentivirus EIAV (equine
infectious anemia virus), which is structurally very similar to HIV, is
transmitted via horsefly.  Presumably HIV could be, also.

   The real reason is that horseflys are messy feeders, and mosquitos
aren't.  No blood goes from mosquito's gut into a new host-- they are
far too conservative of calories for that (mosquito diseases are
transmitted generally via virus or parasite replicating in the mosquito
salivary glands, where it does get injected with the anticoagulant
saliva).  The only direct blood contaminant a mosquito brings is the
tiny amount of blood clinging to the outside of the last part of its
tiny proboscis.  Since that amount is much smaller than on a needle,
and since HIV is generally present in low concentration, the risk from
this is very, very small.  Indeed, it's only about 1 in 500 from a
needle.

   Those who share "needles", BTW, get infected generally because they
also share syringes/bulbs, which are often contaminated by blood
deliberately drawn back up to smoothly dilute and rinse out drug in a
syringe.

                                      Steve Harris, M.D.