norm@mtgzy.att.com (n.e.andrews) (08/02/89)
Why does a mosquito bite swell up and itch? What goes on under the skin? How does the mosquito benefit from it? Can the mosquito's poison be used to human advantage? Any pointers to literature? Thank you! Norm Andrews AT&T Bell Laboratories Room MT-2C402 200 Laurel Avenue Middletown, New Jersey 07748 (201)957-5786 att!mtuxo!mtgzy!norm
scb1@tank.uchicago.edu (Sam Blackman) (08/11/89)
Well, I guess I'll take it point by point ... >Why does a mosquito bite swell up and itch? Because you are experiencing a localized allergic reaction (as opposed to a systemic allergic reaction) to the mosquito's saliva, which is injected (amongst other things) into your skin. This allergic reaction (ala IgE) causes the release of histamine, which is a vasodialator. The local vasodialation results in the redness and swelling, and I believe that the release of histamine from mast cells causes the itching. >What goes on under the skin? See above ... >How does the mosquito benefit from it? Well first off, only female mosquito's "bite" us. What they are really doing is drawing blood from us. The mosquito has a tube-like probiscus which is inserts into us (along with an anesthetic-type substance). The mosquito then injects it's saliva and withdraws blood, which it uses as food. >Can the mosquito's poison be used to human advantage? I hardly know a poison that is used to human advantage - human demise, that's another story. The mosquito is poison-free - what causes the reaction is it's saliva - and I don't see much human use in that ... >Any pointers to literature? If you're interested in localized allergic reactions, IgE-type reactions, basic immunology, etc. you might want to hit the Rutgers Bookstore and check out their medical books section ... -- Samuel C. Blackman ! InterNet : scb1@tank.uchicago.edu ! Link : ST0426 Apple Student Rep. ! Disclaimer : Does anybody really care what I'm 1155 East 60th St. #325 ! writing anyway ??? Chicago, IL 60637 ! Telephone : (312) 702-8630 (w) (312) 947-8652 (h)
arf@chinet.chi.il.us (Jack Schmidling) (08/14/89)
nti/e6 Article 2376 (3 more) in sci.bio: From: scb1@tank.uchicago.edu (Sam Blackman) Subject: Re: What's the Why and How of Mosquito Bites? >>How does the mosquito benefit from it? Blackman says: >Well first off, only female mosquito's "bite" us. What they are really doing is drawing blood from us. The mosquito has a tube-like probiscus which is inserts into us (along with an anesthetic-type substance). The mosquito then injects it's saliva and withdraws blood, which it uses as food. ARF says: Just one detail you left out. The saliva contains an anti-coagulant for reasons which should be obvious. Also, the female needs one full blood meal per clutch of eggs. The blood provides the protein needed for egg production. This brings up an interesting discussion.......... Does anyone have any, non-political, "real" data on studies of AIDS transmission via blood sucking insects? Don't bother posting sanitized media hype or surgeon general dis-information. I am looking for source infomation. The Amateur Radio Forum (arf)
heumann@hpmtlx.HP.COM ($John_Heumann@hpmtljh) (08/14/89)
> I hardly know a poison that is used to human advantage...
Well, gee there's atropine, belladona, digitalis all of which are quite
toxic but also find legitimate medicinal use. In fact I'd almost go to
the other extreme: most drugs are poisonous and their medicinal
use involves careful titration of dosage to stay under the toxic range.turpin@cs.utexas.edu (Russell Turpin) (08/14/89)
In article <9263@chinet.chi.il.us>, arf@chinet.chi.il.us (Jack Schmidling) writes: > Does anyone have any, non-political, "real" data on studies > of AIDS transmission via blood sucking insects? > > Don't bother posting sanitized media hype or surgeon general > dis-information. > > I am looking for source infomation. A common misunderstanding about mosquito vectored diseases is that mosquitos act simply to transfer blood from victim to victim. This is not true. The diseases that mosquitos vector, such as malaria and dengue fever, are ones where the disease agent also infects the mosquito. The malarial plasmodium, for example, undergoes a lifecycle in the mosquito, whose final stage is reproduction in the mosquito's salivary glands. When the mosquito bites, it injects its saliva into the host animal, and with this, the new generation of the malarial organism. The mosquito very efficiently draws blood in only one direction. For this reason, it does not act to transfer blood from host to host and has not been a significant vector for blood borne diseases which do not infect the mosquito, eg, syphillis, hepatitus, etc. An unfortunate fact of biology is that its facts are often matters of probability. It may not be impossible for you to get HIV exposure from a mosquito, anymore than it is impossible for you to get syphillis from a toilet seat or pregnant by fellatio. (Craig Werner posted a report where the last actually occurred in a very strange case in Africa.) There is a greater likelihood of a plane crashing in your house and killing you tonight than any of these. If one is to discuss these things intelligently, one must learn to handle probabilities. Before one worries about catching AIDS from a mosquito, one should worry about all the planes that fly overhead. The epidemiological evidence backs what is known about the mechanism of mosquito borne diseases. The epidemiology of mosquito borne diseases has been extensively studied in the various malarial areas. If HIV were vectored by mosquitos the way malaria is, this would stand out in its spread in Africa. It doesn't. The Scientific American had an issue devoted to AIDS several months ago that included an article on its epidemiology. This article included some references to primary research. Russell
chappell@aylmer.uchicago.edu (Chappell) (08/15/89)
In article <6704@cs.utexas.edu> turpin@cs.utexas.edu (Russell Turpin) writes: >An unfortunate fact of biology is that its facts are often >matters of probability. It may not be impossible for you to get As we biometricians all know, it may not be such an unfortunate fact. These matters of probability make the study of biology much more interesting. So many fascinating issues in genetics, epidemiology, and almost all other subfields of biology exist because they are not set in a stark deterministic context. >HIV exposure from a mosquito, anymore than it is impossible for >you to get syphillis from a toilet seat or pregnant by fellatio. >(Craig Werner posted a report where the last actually occurred in >a very strange case in Africa.) There is a greater likelihood of All right, I'll bite (perhaps I should rephrase that). Pregnancy by fellatio? A low blow to zero-population-growthists. Did anybody store C.W.'s post? I would appreciate a copy. Thanks, >Russell -Spike.
turpin@cs.utexas.edu (Russell Turpin) (08/15/89)
In article <4987@tank.uchicago.edu>, chappell@aylmer.uchicago.edu (Chappell) writes: > All right, I'll bite (perhaps I should rephrase that). Pregnancy by > fellatio? A low blow to zero-population-growthists. Did anybody store > C.W.'s post? I would appreciate a copy. ... I hope CW saved his posting. In case he doesn't repost, I will relate what I remember. (This will be an interesting experiment -- if Craig does repost, we can compare how closely my memory tracks what I read a few months ago.) It was a story reported in a medical journal. A woman came into a South African hospital obviously pregnant. The major problem was that she had no vagina -- only a dimple where one should have been. Her baby was delivered by Caesarean, the mother was scheduled for reconstructive surgery, and the doctors began puzzling over this provably virgin birth. It turned out that the woman had entered the same hospital nine months earlier with several knife wounds in her abdomen, including at least one that lacerated her intestines. She had been treated and released. The wounds were the result of a fight with another woman over a man. At this point, the wounded woman's preferred mode of sexual activity, as well as the route the father's sperm swam should be fairly obvious. The reason I brought this story up yet again is to show the foolishness of those who argue that because a disease could conceivably be caught in some way, this mode must be protected against. The biological world is not one of mathematics, or even one whose laws are as inviolable as those of physics. It is the very messy world in which we all live and is full of once in a lifetime incidents. When a doctor says that shaking hands does not spread syphillis, this does not mean that it is absolutely impossible for a person to catch syphillis by shaking hands, and finding one such case does not disprove the doctor's claim. What is meant is that catching syphillis by shaking a stranger's hand ranks, as risks are measured, way down there with becoming pregnant by giving fellatio or dying from a 747 crashing on you. Russell
arf@chinet.chi.il.us (Jack Schmidling) (08/16/89)
virgin/e6 Article 2384 (3 more) in sci.bio: From: turpin@cs.utexas.edu (Russell Turpin) Subject: Re: What's the Why and How of Mosquito Bites? Summary: Mosquitos as vectors of diseases. In article <9263@chinet.chi.il.us>, arf@chinet.chi.il.us (Jack Schmidling) writes: > Does anyone have any, non-political, "real" data on studies > of AIDS transmission via blood sucking insects? Turpin says: >The diseases that mosquitos vector,such as malaria and dengue fever, are ones where the disease agent also infects the mosquito. The malarial plasmodium........... ARF says: You come dangerously close to evading the issue by changing the subject to complex, multi-species vectors. However, you seem to make a case for the ease with which AIDS could be vectored because it requires only a simple blood transfer. The virus need only stay alive long enough for the transfer. >The mosquito very efficiently draws blood in only one direction. For this reason, it does not act to transfer blood from host to host........... ARF says: Have you never smashed a blood-gorged mosquito sitting on your arm? All the senario needs to transfer, is for the mosquito to have taken a prior, partial meal, from an AIDS carrier. Not quite as improbable as your virgin birth! Certainly not improbable enough to ignore as seems to be the case. The Amateur Radio Forum (arf) sorry for the sp but can't edit and did't see before
alan@apptek11.uucp (Alan Algustyniak) (08/17/89)
> ARF says: > Have you never smashed a blood-gorged mosquito sitting on your arm? All the > senario needs to transfer, is for the mosquito to have taken a prior, partial > meal, from an AIDS carrier. > Not quite as improbable as your virgin birth! > Certainly not improbable enough to ignore as seems to be the case. This reasoning seems convincing on the theoritical level, but one has to wonder why, then, are not ALL sub-Saharan people infected by now? I have read that mosquitos are not as attracted to black skin as they are to white skin, but by how much, I don't know. BTW, if mosquitos need blood to propogate, then how do the ones deep in the swamps do it? Where do they find their victims? Oh, so that's what those bumps on the backs of alligators are...:-) alan
turpin@cs.utexas.edu (Russell Turpin) (08/17/89)
ARF says: > > Have you never smashed a blood-gorged mosquito sitting on your arm? All > > the senario needs to transfer, is for the mosquito to have taken a prior, > > partial meal, from an AIDS carrier. No, it also requires blood from the last meal to be left in the mosquito's proboscis, that the mosquito's proboscis is still in your arm, and that you smash the mosquito in such a fashion that the blood is injected into your arm. The chance of developing an infection depends (at low levels) on the amount of exposure to the disease causing agent. Thus, not all needle stick accidents in hospitals and labs involving active HIV samples result in HIV infection. > > Not quite as improbable as your virgin birth! > > Certainly not improbable enough to ignore as seems to be the case. The chance of HIV infection from smashing a mosquito may be greater than the chance of virgin birth, but if this mode of transmission occurs, it is so rare that it does not show up in epidemiological studies in Africa and elsewhere. If it worries you, the solution is obvious: don't slap that mosquito. In article <24875@joyce.istc.sri.com>, alan@apptek11.uucp (Alan Algustyniak) writes: > BTW, if mosquitos need blood to propogate, then how do the ones deep in > the swamps do it? Where do they find their victims? Oh, so that's > what those bumps on the backs of alligators are...:-) There are many, varied species of mosquitos. Not all require blood, and of those which do, many are happy with animal hosts, including some that are responsible for human diseases. The anopheles mosquito that spreads malaria, for instance, prefers cattle to people. One of the reasons for the retreat of malaria from England in the 17th century was an increase in cattle herds. The mosquitos moved from human to cattle hosts, and because cattle are not sucseptible to malaria, the chain of infection was curtailed. (William McNeill, "Plagues and People", p 218.) Russell
kauffman-jon@CS.YALE.EDU (Jon Kauffman) (08/17/89)
Um, I seem to remember an article which describes a study in St
Augustine, Florida, a locale know for its mosquito population.
The idea is that many other things being equal (I cannot comment on how
equal they really are), if mosquitos were a vector, then all age groups
would be affected equally, since mosquitoes aren't particularly choosy.
The study concluded that this was not the case: there were few (maybe none,
at least in the sample, don't really remember) cases among the elderly and
pre-adolescents. I assume that the inhabitants of the city all had about
the same chances of being bitten.
I apologize for not being able to quote a real source, hopefully someone
in net.land can help me out. If someone wants to claim that the
elderly and young are protected in some other way, or that they somehow
avoid mosquito bites, you're welcome to do so; I claim no expertise in
epidemiology/insect vectors.
Just hoped I could muddy the waters a bit more.
/jon
======================================================================
Jonathan Kauffman kauffman@cs.yale.edu
Yale CS Facility {harvard,decvax}!yale!kauffman
======================================================================sue@gtx.com (Sue Miller) (08/17/89)
Jack Schmidling writes: - -Turpin says: - ->The diseases that mosquitos vector,such as malaria and dengue fever, are ->ones where the disease agent also infects the mosquito. The malarial ->plasmodium........... - - -ARF says: - -You come dangerously close to evading the issue by changing the subject to -complex, multi-species vectors. However, you seem to make a case for the -ease with which AIDS could be vectored because it requires only a simple -blood transfer. The virus need only stay alive long enough for the transfer. I don't see where Russell changed the subject. He states very clearly that the only diseases which mosquitoes can transmit are ones which also infect the mosquito. The mosquito does not transfer blood from host to host. The mosquito sucks a bunch of blood, then digests it. The host gets a shot of mosquito saliva per each bite, which may harbor bacteria/virii if the the infectious organism can live in the mosquito. HIV has shown itself to be unable to survive in a mosquito, therefore you cannot get AIDS from a mosquito bite. - ->The mosquito very efficiently draws blood in only one direction. ->For this reason, it does not act to transfer blood from host to ->host........... - -ARF says: - -Have you never smashed a blood-gorged mosquito sitting on your arm? All the -senario needs to transfer, is for the mosquito to have taken a prior, partial -meal, from an AIDS carrier. So don't squash a mosquito on your arm when you have open sores on it. - - -Certainly not improbable enough to ignore as seems to be the case. Huh? Did you mean to say that you think this is something to worry about? I'd be morely to worry about a 747 falling down on my house. That, at least, has documented occurrences. Researchers have spent many hours looking for insect vectors for the HIV/HTLV (whatever) group of virii and have thus far found none. There is no mechanism, and no corroborative statistical evidence (like patterns of AIDS infection matching up with other mosquito-borne infections), so I dunno why anyone'd be nervous. -- listen: there's a hell of a good universe next door; let's go. __________________________________ ee cummings |Sue Miller ...!sun!sunburn!gtx!sue|
scb1@tank.uchicago.edu (Sam Blackman) (08/17/89)
In article <1840001@hpmtlx.HP.COM> heumann@hpmtlx.HP.COM ($John_Heumann@hpmtljh) writes: >> I hardly know a poison that is used to human advantage... > >Well, gee there's atropine, belladona, digitalis all of which are quite >toxic but also find legitimate medicinal use. In fact I'd almost go to >the other extreme: most drugs are poisonous and their medicinal >use involves careful titration of dosage to stay under the toxic range. Well, forgive my innocence (or rather lack of whole-brain thinking) ... I rapidly withdraw that remark and concede the point ... Sam -- Samuel C. Blackman ! InterNet : scb1@tank.uchicago.edu ! Link : ST0426 Apple Student Rep. ! Disclaimer : Does anybody really care what I'm 1155 East 60th St. #325 ! writing anyway ??? Chicago, IL 60637 ! Telephone : (312) 702-8630 (w) (312) 947-8652 (h)
pell@boulder.Colorado.EDU (Anthony Pelletier) (08/17/89)
In article <9279@chinet.chi.il.us> arf@chinet.chi.il.us (Jack Schmidling) writes: > >> Does anyone have any, non-political, "real" data on studies >> of AIDS transmission via blood sucking insects? Yes, and Turpin gave you a reference, of sorts, the Sci Am issue devoted to AIDS. The epidemiological data ARE "real data." If by "real data" you mean has anyone filled a room up with mosquitos and had them feed on an AIDS patient, then put a non-infected person in the room, well, no ARF, I doubt anyone has done that experiment. >Turpin says: > > [What Turpin said was clear and informative. Re:probability in Bio and such] > >ARF says: > [Very little of note, as usual] >ARF says: > >Have you never smashed a blood-gorged mosquito sitting on your arm? All the >senario needs to transfer, is for the mosquito to have taken a prior, partial >meal, from an AIDS carrier. > >Not quite as improbable as your virgin birth! Russel gave the reasons why it is unlikely. As he said, all the diseases that are transmitted by the beasts have the mosquito as a host. I can't improve on his essay reguarding the thing being technically possible, but highly improbable. As a molecular biologist, I am quite impressed by what one can learn from epidemiology. Did you know, for example, the the epidemiologists predicted the causative agent would be a virus, based on the studies in Africa? I consider the epidemiological data to be "real data." In any case, they are the best data we are likely to get, since noone is going to do the controled experiment. Some reports on epidemiology that can be found in the Sci. Am. to which Russel referred you might enlighten you a bit. It is perhaps not as rare as a virgin birth, but very unlikely for AIDS to be transmitted by mosquitos. The data you claim to seek are right there for you. Read them. -tony
hjsdvm@ziebmef.uucp (Howard J. Scrimgeour) (08/18/89)
In article <5399@mtgzy.att.com> norm@mtgzy.att.com (n.e.andrews) writes: > >Why does a mosquito bite swell up and itch? It's an allergic reaction. The body reacts to the presence of foreign substances by releasing histamine, serotonin, and other active substances from basophils and mast cells. This causes leakage of fluid from capillaries, infiltration of inflammatory cells, and other signs of inflammation. It's the same reaction as the "hives" you get with some other allergies. >What goes on under the skin? >How does the mosquito benefit from it? The foreign substance in this case is an anticoagulant protein in the mosquito's saliva. The benefit to the mosquito (obviously) is that it keeps the blood from clotting in the mosquito's mouth parts and digestive tract. >Can the mosquito's poison be used to human advantage? Not really. We have lots of good anticoagulants, and they don't produce allergic reactions. >Any pointers to literature? Not that I know of. > >Thank you! You're welcome. +------------------------------------------------------------------------+ | Howard J. Scrimgeour, D.V.M. | | hjsdvm@ziebmef.uucp CIS:75126,2744 | | uunet!{utgpu!moore,attcan!telly}!ziebmef!hjsdvm | | "We also walk dogs..." | +------------------------------------------------------------------------+
arf@chinet.chi.il.us (Jack Schmidling) (08/18/89)
mammals/e6 Article 2393 (2 more) in sci.bio: From: alan@apptek11.uucp (Alan Algustyniak) Subject: Re: What's the Why and How of Mosquito Bites? >> ARF says: >> Have you never smashed a blood-gorged mosquito sitting on your arm? All the senario needs to transfer, is for the mosquito to have taken a prior, partial meal, from an AIDS carrier. >> Not quite as improbable as your virgin birth! >This reasoning seems convincing on the theoritical level, but one has to wonder why, then, are not ALL sub-Saharan people infected by now? ARF says: The same reason, everyone attending a homosexual picknic does not get AIDS. Recognizing a transfer mechanism does not throw the probability arguments to the winds. >I have read that mosquitos are not as attracted to black skin as they are to white skin, but by how much, I don't know. Arf says: I don't know about black but I learned long ago not to go botanizing in a red shirt. >BTW, if mosquitos need blood to propogate, then how do the ones deep in the swamps do it? ARF says: I know not what swamps you have in mind but on this planet, they all have large populations of mammals. (Russell Turpin) says: >No, it also requires blood from the last meal to be left in the mosquito's proboscis, that the mosquito's proboscis is still in your arm, and that you smash the mosquito in such a fashion that the blood is injected into your arm. ARF says: I never suggested that the blood would neatly squirt back into the arm. The proboscis would no doubt be destroyed by the smashing. I do suggest that you have on your arm several drops of AIDS contaminated blood sitting on an open, albeit small, wound. You also have contaminated blood on the smashing hand. If you have a sore on your hand, scratch your nose, rub yours eyes, etc., etc., there are possibilities that can not be swept under the carpet. >The chance of HIV infection from smashing a mosquito may be greater than the chance of virgin birth, but if this mode of transmission occurs, it is so rare that it does not show up in epidemiological studies.... ARF says: Mosquito transmission does not show up in epidemiological studies because of the absurdity of asking every AIDS victim: "Have you ever been bitten by a mosquito?" What would you do with the data? The only conclusion you could logically arrive at is that AIDS is caused by mosquitoes because it is the only exposure mechanism they all have in common. (Jon Kauffman) says: >Um, I seem to remember an article which describes a study in St Augustine, Florida, a locale know for its mosquito population. >The idea is that many other things being equal (I cannot comment on how equal they really are), if mosquitos were a vector, then all age groups would be affected equally, since mosquitoes aren't particularly choosy. ARF says: All of the above is precisely the non-rigorous, anecdotal, rhetorical, negative, dis-information that has been fed to us in lieu of the results of a rigorous, scientific study to find out if AIDS {can} be spread by blood sucking insects. All we hear are reasons why it can't be spread but not a single study with real virus, real insects and real lab animals and/or people. The Amateur Radio Forum (arf)
arf@chinet.chi.il.us (Jack Schmidling) (08/19/89)
cite/e6 Article 2400 in sci.bio: From: sue@gtx.com (Sue Miller) Subject: Re: What's the Why and How of Mosquito Bites? > I don't see where Russell changed the subject. He states very clearly that the only diseases which mosquitoes can transmit are ones which also infect the mosquito. ARF says: I doubt that he said that. If he did, he is wrong. Did you ever see mosquito die of malaria? >HIV has shown itself to be unable to survive in a mosquito, therefore you cannot get AIDS from a mosquito bite. ARF says: I didn't know that a virus could conduct a study. If you ment to say that studies have shown the above, the object of this discussion is to review the studies not repeat the media hype about them. > Researchers have spent many hours looking for insect vectors for the HIV/HTLV (whatever) group of virii and have thus far found none. ARF says: Citations please! >There is no statistical evidence (like patterns of AIDS infection matching up with other mosquito-borne infections), bla...bla...bla... ARF says: I have already pointed out the absurdity of asking AIDS victims if they were ever bitten by a mosquito. The Amateur Radio Forum (arf)
arf@chinet.chi.il.us (Jack Schmidling) (08/20/89)
real/e6 Article 2404 (3 more) in sci.bio: From: pell@boulder.Colorado.EDU (Anthony Pelletier) Subject: Re: What's the Why and How of Mosquito Bites? In article <9279@chinet.chi.il.us> arf@chinet.chi.il.us (Jack Schmidling) writes: > >> Does anyone have any, non-political, "real" data on studies of AIDS transmission via blood sucking insects? Pelletier says: >If by "real data" you mean has anyone filled a room up with mosquitos and had them feed on an AIDS patient, then put a non-infected person in the room, well, no ARF, I doubt anyone has done that experiment. ARF says: I think we all know that "real", to a scientist, means the results of rigorous, controlled experimentation, the results of which lead to a conclusion. Show me another disease in which "real" data consists of everything but controlled experiments. >As a molecular biologist, I am quite impressed by what one can learn from epidemiology......In any case, they are the best data we are likely to get, since noone is going to do the controled experiment. ARF says: As a scientist, I am more impressed by the results of controled experiments. If you can't or won't do them, that is your privilege, but you can not manufacture the data and call it SCIENCE. The Amateur Radio Forum (arf)
turpin@cs.utexas.edu (Russell Turpin) (08/22/89)
ARF says: > Mosquito transmission does not show up in epidemiological > studies because of the absurdity of asking every AIDS > victim: "Have you ever been bitten by a mosquito?" Which shows that ARF understands very little about epidemiology. While individual case histories are very important, many questions can be answered by studying evidence of a more statistical nature. What is the age distribution of those infected? In what regions is the disease most prevalent? Does infection incidence vary with season? What socio-economic factors correlate with infection? How do these factors correlate with exposure to possible vectors? When statistics of these kinds are combined with information from case histories, it is possible to learn a lot about the nature of transmission of a disease. A mosquito vectored disease displays particular statistical patterns in these areas. These patterns will show up even if it is a minor mode of transmission. If such patterns don't show up at all, it's because mosquito transmission is extremely rare. One doesn't have to ask people "Have you ever been bitten by a striped mosquito" in order to find out that a disease is transmitted by a particular kind of mosquito. As I previously noted, such knowledge, like the evidence, is statistical in nature. No one can prove that mosquito transmission of HIV is impossible or has never happened. Of course, the same can be said for syphillis. But if it occurs, it is so rare that the epidemiological evidence does not show it. Again, the "Scientific American" issue on AIDS had an article on its epidemiology with references to various studies, and these references will themselves have references. If you want to study this matter in depth, you can find out precisely what research has been done and by whom and how thoroughly, but don't expect people on the net to do your library work for you. Maybe the epidemiological research is sloppy or insufficient, and you would be doing us all a favor by doing more, better. Go to it. We would all welcome better, surer knowledge on this disease. If mosquito transmission of HIV is rare, we will never know just how improbable it is. To know this, one would have to let a cloud of mosquitos take partial meals from a group of people who are HIV positive, transfer the mosquitos into an auditorium in which there were a hundred thousand people without HIV exposure, have these subjects slap the mosquitos that bit them, track them for several months to see who seroconverted, and make sure that those who did were not exposed by other means. (If none seroconverted from slapping mosquitos, that still doesn't mean it is impossible. Perhaps if one used a million subjects ...) Even excluding ethical considerations, such an experiment is clearly impractical, and the results would not be very helpful. What, pray tell, would you do with a fact like "If an anopholes g. takes a partial meal from an HIV positive person and within ten minutes bites an HIV negative subject who then slaps the mosquito and smears its blood over the subject's skin and fails to wash it away for the next half hour, then the subject's odds of seroconverting is .00000167"? Like I said before, if the risk worries you, don't slap that mosquito. Personally, when I'm out and about I worry much more about water moccasins. If I were to worry about mosquito vectored diseases, it would be dengue fever (of which we had a few cases in Texas some years ago) and equine encephalitis. You don't have to slap that mosquito to get these, and they may kill you quicker to boot! Are you any relation to ALF? You two seem to think on the same wavelength. Russell
binkley@boulder.Colorado.EDU (Jon Binkley) (08/22/89)
In article <9300@chinet.chi.il.us> arf@chinet.chi.il.us (Jack Schmidling) writes: >From: sue@gtx.com (Sue Miller) >Subject: Re: What's the Why and How of Mosquito Bites? > >> I don't see where Russell changed the subject. He states >very clearly that the only diseases which mosquitoes can >transmit are ones which also infect the mosquito. > >ARF says: > >I doubt that he said that. If he did, he is wrong. Did you >ever see mosquito die of malaria? I'm amazed by this guy. How could someone so bloody ignorant be so arrogant? Why don't you look into the subject a little more before you stick your foot in your mouth again, arf ol' boy? -Jon Binkley
turpin@cs.utexas.edu (Russell Turpin) (08/22/89)
ARF says: > I think we all know that "real", to a scientist, means the > results of rigorous, controlled experimentation, the results > of which lead to a conclusion. > > > As a molecular biologist, I am quite impressed by what one > > can learn from epidemiology... > > As a scientist, I am more impressed by the results of > controled experiments. If you can't or won't do them, that > is your privilege, but you can not manufacture the data and > call it SCIENCE. Who, pray tell, is manufacturing data? The major fabrication I see is the specious implication that something is scientific evidence only if it is garnered by controlled experiment, and that observation and statistical analysis do not count. Since Galen, careful observation has been a cornerstone of medical science, and it remains so today, though our methodological requirements have been refined over the centuries. There are many sciences in which certain crucial evidence can only be gathered by observation, because controlled experimentation is impossible. These include astronomy -- we cannot create stars in the laboratory; geology -- there is only one earth to study; and biology -- the epidemiology of every disease is observed only, since no one would purposely introduce a disease into a control population to see if its spread matches what is predicted by theory, not to mention the fact that one cannot arbitrarily prepare test populations. In all of these, laboratory experiments complement observation. The physical theories underlying stellar evolution and geological processes are tested by thousands of experiments. The biological and chemical mechanisms of many disease organisms, including HIV, are studied both in vitro and in animal hosts. Perhaps it is because ARF is confused about the nature of scientific work that he is so suspicious of the way scientists are studying AIDS. There have been no controlled experiments to test whether syphillis can be transmitted by mosquito, or whether typhus can be spread by air droplets as well as lice. If ARF is going to ramble on, perhaps these will provide him more fodder. Russell