>I was watching my Yahoo news ticker today, when I saw a note about a
>possible new way to test for rabies.  What is done is some cells are taken
>from the surface of the cornea, which are then tested for signs of rabies.
 
Don't get your hopes up for this as a new test.  It's not new.  It's not
considered reliable either, any more than any other test for rabies.  I
read mostly stuff for testing humans, and if they can't do early detection
for humans, you can bet it isn't available for any other critter (without
killing them).
 
The problem is that there are lots of false negatives in the various tests
available, until the disease is so advanced it's obvious.  The result is
that in human medicine, even with false positives, if rabies is suspected
treatment with rabies antigen is done anyway.  (And it doesn't work- the
treatment is followed by the patient dying.  I think two human patients are
documented as ever surviving, and when I was in college the vet who ran the
agriculture school said the one case he knew of the fellow would have been
better off dying, that's how bad the brain damage was.) That's as good as it
gets right now.  Once symptoms appear, the virus has destroyed brain tissue.
The salivary glands, CNS (central nervous system-brain and spinal cord) tend
to be infected at about the same time.  That's an evolutionary thing that
has kept the transmission pattern going.  I believe (but am not certain)
that the corneas show up positive at about the same time.  If earlier than
not by much.
 
Other testing methods include checking cerebral spinal fluid, and skin
samples from the nape of the neck (note the location is near the spine).
 
The virus is adapted to grow in nerve tissue and grows along the nerve
pathways toward the brain (actually I think in both directions, but
eventually reaching the brain).  I think this makes it difficult to test for
until it reaches a large area of nerve tissue as in the brain and salivary
glands.
 
The Compendium changes will put an end to a lot of the testing, but not all
of it.  Keep in mind that under some circumstances dogs and cats still get
tested too.  What it WILL do is cut way down on the obviously unnecessary
kill and test of most vaccinated apparently healthy ferrets.  If a ferret,
even a vaccinated one is involved in a reported bite incident and is acting
suspiciously aggressive or showing neurological symptoms they may still be
put down.  Sukies reminder to educate vets about the symptoms of insulinoma
was right on target.
 
For comparison, in 1995 NY tested 2,284 cats, of which 27 were positive.
 
That statistic is courtesy of the NY Rabies testing lab.  In that same year
39 ferrets were tested, 1 positive (for raccoon strain of virus).  That is
the only confirmed case of ferret rabies in NY so far.
 
-Ilena Ayala
[Posted in FML issue 2228]