spel@hippo.ru.ac.za (Dr. Eberhard W. Lisse) (06/14/91)
In <1991Jun12.020736.27657@cbfsb.att.com> Dan_Jacobson@ATT.COM writes: >>>>>> "g" == grx0644 <grx0644@uoft02.utoledo.edu> writes: >g> There is no evidence that the HIV virus can be >g> transmitted via insects bites. Lets look at a mosquito and how it >g> does what it does. >g> It bites its lunch and sucks up some blood. The mosquito then >g> digests the blood with protolytic enzymes that break down all >g> proteins [...] >Just curious, what if a mosquito bites person A for 1/8 second before >being brushed away. Still hungry, it immediately bites person B. >[I remember we went thru this discussion here years ago. I forgot >why the above was disproven also. Please post, not mail.] Well, sigh, it is quite obvious (like a lot on sci.med.folklore). It sucks blood. [In order to preempt the question how the moskito transmits malaria: that parasite goes through a cycle, transmits the gastric wall enters the salivary glands and then goes into the new victim.] Well, well... el ps: flames please per email to <spel@hippo.ru.ac.ZA> :-)-O -- Dr. Eberhard W. Lisse (spel@hippo.ru.ac.ZA) Katatura State Hospital (formerly extel@quagga.ru.ac.za) Private Bag 13215 (Real Soon Now ... el@lisse.NA) Windhoek, Namibia (no FTP yet. [This is Africa :-)-O])
pwallich@uunet.UU.NET (Paul Wallich) (06/14/91)
The strongest evidence that insects don't transmit HIV is epidemiological, and the detailed physical mechanisms come second. If insects could transmit the virus, then the pattern of disease in insect-ridden areas would match the pattern of people who get bitten by insects -- as the pattern of malaria infection does, for example. This means small children, older people, people living nearer to stagnant water for mosquitos e.g. and so forth. The pattern of HIV infection in insect-ridden areas is instead much like the pattern elsewhere: people who are sexually active & people who share needles. (That's the short version, of course. You can do it in longer version, but it's not really worth the trouble. Added to this, of course, is that HIV seems fairly difficult to transmit -- insofar as the blood- borne cases can be quantified, I think they all involve significantly more blood than one mosquito can carry.) paul
Dan_Jacobson@ATT.COM (06/18/91)
>>>>> On 13 Jun 91 18:32:54 GMT, spel@hippo.ru.ac.za (Dr. Eberhard W. Lisse) said: Eberhard> In <1991Jun12.020736.27657@cbfsb.att.com> Dan_Jacobson@ATT.COM writes: >Just curious, what if a mosquito bites person A for 1/8 second before >being brushed away. Still hungry, it immediately bites person B. >[I remember we went thru this discussion here years ago. I forgot >why the above was disproven also. Please post, not mail.] Eberhard> Well, sigh, it is quite obvious (like a lot on sci.med.folklore). Eberhard> It sucks blood. [...] I was thinking of the "dirty IV drug needle" analogy, specifically the outside of the mosquito's "needle"; and that maybe that it is so uncommon for a mosquito to be brushed away from person A after a 1/8 of a second unsatisfying bite and then bite person B that it hasn't shown up statistically (and therefore not something to be much worried about)... >>>>> On 13 Jun 91 21:02:31 GMT, decwrl!well.sf.ca.us!well!pwallich@uunet.UU.NET (Paul Wallich) said: Paul> Added to this, of course, is that HIV seems fairly difficult to Paul> transmit -- insofar as the blood- borne cases can be quantified, Paul> I think they all involve significantly more blood than one Paul> mosquito can carry.) But we are told that microscopic tears in the skin can be a route for transmission (via shared bodily fluids). [please post, not mail replies]
3KSNFZM@vmd.cso.uiuc.edu (Edward A. Lisowski) (06/19/91)
I hesitate to get involved in this discussion because I think think there
are more important issues to worry about. In some ways I can understand
Dan Jacobson's fear of AIDS from insect bites. Several years ago my body
was donated to a medical entomology research project to study the invasion
of Chicago by the Asian tiger mosquito, _Aedes_ _albopictus_ . Part of the
study was to sit in the shade and count mosquito bites per 10 minutes.
Although the person sitting next to me was HIV antibody positive (and his
lover of 15 years had recently died), I was much more worried about other
diseases I could get from mosquito bites, such as encephalitis, dengue,
malaria, etc. (We were in a area with a lot of recent immigrants from Central
America and the Caribbean.)
Back around 1988 (during the Belle Glade brouhaha) someone had a letter in
_Science_ where they ball-park estimated the number of virus particles per
ml of blood of a PWA and what fraction of an ml of blood a mosquito sucks up.
As I recall, it would take, on average, over 1000 bites for one mosquito to
get one virus particle from a PWA.
Now for my cynical view of why insects are not likely to play a role in HIV
tranmission. There are a lot of underemployed entomologits who would love to
get their lips on the great-mother-teat of HIV research. The bottom line is
there is no scientific evidence to support further research in this area.
Both epidemiological data in devloping countries and laboratory data from
insect cell replication experiments rule out insects as playing a role in
HIV transmission.
Ed Lisowski, an underemployed entomologisthlaufman@magnus.acs.ohio-state.edu (Harry B Laufman) (06/21/91)
Without permission, typographical errors are HBL's.
From NATURAL HISTORY, 7/91, page 54:
_Can Mosquitoes Transmit AIDS?_
Acquired Immune Deficiency Syndrome (AIDS), the deadly epidemic
caused by the HIV virus, is most often transmitted by con-
taminated hypodermic needles or through sexual contact. Since
mosquitoes feed on human blood and may attack a series of
individuals, the question arises: Can you get AIDS from a
mosquito bite?
According to Jonathan F. Day, of the University of Florida's
Medical Entomology Laboratory, insects can transmit viruses
in two ways, mechanically and biologically. With mechanical
transmission, infected blood on the insect's mouthparts might
be carried to another host while the blood is still fresh and
the virus still alive. Infection by this means is possible
but highly unlikely, because mosquitoes seldom have fresh blood
on the outside of their mouthparts. Mechanical transmission
does occur in horses, however, with equine infectious anemia,
a virus closely related to AIDS and transmitted by horseflies.
These flies are "pool feeders"; their bite causes a small
puddle of blood to form, and they immerse their mouthparts,
head and front legs while lapping it up. If disturbed, however,
they quickly move on to another horse, where the fresh blood of
the two hosts may mingle. Blood feeding mosquitoes are much
neater and more surgical; they insert a tube for drawing blood,
and by the time they are ready for their next meal, even on a
second host following an interrupted meal, any viruses from the
first meal are safely stored in their midgut.
With biological transmission, the pathogen must complete a
portion of its life cycle within a carrier, or vector, species.
Protozoans that cause malaria, for instance, go through an
extremely complex cycle inside the mosquito, eventually con-
gregating in the salivary glands, from which they may infect
avian, primate or reptilian hosts, depending on the malaria
species. The HIV virus, however, does not replicate or develop
in the mosquito; once in the insect's gut, the virus quickly
dies. Repeated studies since 1986 show that AIDS-infected blood
fed to mosquitoes and other arthropods does not live to be
passed on and that there is no biological-transmission cycle of
AIDS in blood-feeding arthropods, which frequently ingest the
virus as part of their blood meal. -R.M.
--------------------------------
Regards, Harrington hlaufman@magnus.acs.ohio-state.edu