Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!gatech!bloom-beacon!usc!cs.utexas.edu!turpin
From: turpin@cs.utexas.edu (Russell Turpin)
Newsgroups: sci.bio
Subject: Re: What's the Why and How of Mosquito Bites?
Summary: Mosquitos as vectors of diseases.
Message-ID: <6704@cs.utexas.edu>
Date: 14 Aug 89 15:48:02 GMT
References: <5399@mtgzy.att.com> <4948@tank.uchicago.edu> <9263@chinet.chi.il.us>
Organization: U. Texas CS Dept., Austin, Texas
Lines: 47

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