RE: DR Eleanor Kellon's Comments WNV Vaccine

[Don Pollock <donp@dcr.net>]

I had posted this to ridecamp last week as I had a question about the vaccine
when it was announced it would be available in Kentucky.  At that time no
occurrence was noted of WNV. Things have changed though but I think I am still
going to heed her advice. Until at least next year when there may be something
besides a provisional vaccine available.

Snip> Message: 17
   Date: Mon, 27 Aug 2001 09:30:18 -0000
   From: kell@epix.net
Subject: Re: RE West Nile Vaccine for horses

The West Nile vaccine has been granted only a conditional approval, 
based on the results of initial safety studies. It has NOT been 
proven to work.  The company has shown only what is called a 
"reasonable expectation of efficacy" - which means when they inject 
the vaccine they get an antibody response.  Just about any vaccine is 
going to give you an antibody response.  The question is whether the 
antigenic portions of the virus used in making the vaccine result in 
antibodies that will actually be effective in protecting the horse.  
The best way to demonstrate this is with challenge studies.  Horses 
are vaccinated and after this are deliberately given a dose of the 
virus to see if they are protected from illness.  This has NOT been 
done with this vaccine.  Researchers around the world have been 
working on trying to develop an effective West Nile vaccine for many 
years with limited or no success in challenge studies.

Also have to realize that vaccination will cause the horse to test 
positive for West Nile which can interfere with diagnostics if the 
animal does become ill and could cause problems with exporting the 
horse (shouldn't, but could).

Vaccination after September 1st is largely a waste of time anyway.  
This disease is spread by mosquitos, which pick up the virus when 
feeding on infected birds.  While many cases continue to appear until 
the end of September/October, when you factor in the delay between 
time of vaccination and time it takes for an effective vaccine to 
actually work, you're pretty much at the end of mosquito season 
anyway.

There have been 35 confirmed cases of equine West Nile so far this 
year - one in PA, one in GA and the rest in northern Florida.  There 
has been no reported West Nile virus activity in Kentucky - in birds, 
mosquitos or mammals, either this year or last year.  
.

Eleanor
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