Ridecamp: Re: [RC] West Nile

In a message dated 06/08/2002 8:58:44 AM Eastern Daylight Time, 
cmcgraw@xxxxxxxxxxxxx writes:

<< Hello:  I'm  someone who just scans Endurance Net archives, and I saw the
 messages concerning West Nile Virus.  None of the details were included,
 however.  Would you mind letting me know what the information was?  I too
 have just given my horses the first shot.
 Thanks, Colleen McGraw
              Ann Arbor, Mi. >>

Hi Colleen!  I guess the original post came to me but never made it to 
ridecamp.  After reading it I am undecided as to whether or not to go ahead 
with the second shot.  Seems a waste of money, on top of being (at best) 
ineffective, and (at worst) dangerous.  On the other hand, it seems that if 
there is to be an immune effect at all, it requires the second shot, and now 
that I've already gone ahead with the first ...?  Any comments (especially 
from traditional and holistic practicing vets!) either for or against going 
ahead with the second shot will be greatly appreciated.  BTW, King David (my 
horse) has shown absolutely no ill effects (thus far) from the vaccine, nor 
has the 20 yr. old boarded mare who also received it.  My 30 yr. old gelding 
(Raftige, aka Tash) never gets any vaccines ... hasn't for most of his life, 
except for the occasional tetanus.  I've owned him since he was 3.  He's been 
as healthy as a horse all this time, and still is.
    Anyway, Here is the original post in it's entirety:

Subj:    West Nile
Date:   06/06/2002 10:26:48 PM Eastern Daylight Time
From:   donp@xxxxxxx (Don Pollock)
To: rainbow@xxxxxxxxxxx
CC: ridecamp@xxxxxxxxxxxxx (Ridecamp), Trishmare7@xxxxxxx

Hello fellow Ridecampers.  I asked the same question to Dr. Kellon at the 
Horse Science digest.  I will include what she and some other folkes said.  
The Vets have been recommending the vaccine here in Kentucky.  That is what 
promped me to ask Kellon about it.
There are three cut and paste e-mails here

Message 1

Snip>Message: 14
   Date: Sat, 25 May 2002 11:23:11 -0000
   From: "drkellon" <kell@xxxxxxxx>
Subject: Re: West Nile Vaccine

The West Nile vaccine remains completely unproven at this point.  Ft.
Dodge has been talking about doing challenge studies since last year
but no word on results yet.  Essentially all information on how the
vaccine is performing so far is coming from data that Florida is
accumulating on vaccine status of West Nile Horses.  It became
apparent very quickly that a single dose of the vaccine is not
protective. The full series called for 2 injections three weeks apart.
Vaccine use in Florida last year did not really get rolling until
about the end of August.  There were 20 confirmed West Nile positives
in fully vaccinated horses, out of a total of about 180 cases, in
Florida in the time period after the vaccine came into full use.
That's 11%.  In 2002, from January to end of March, 4 of the 14
positive or suspect cases  were in fully vaccinated horses - 29%.

There are three possible explanations for fully vaccinated horses
showing West Nile symptoms anyway:

1. The vaccine didn't work
2. The vaccine didn't have time to work
3. The vaccine itself caused the symptoms

No one wants to believe the vaccine didn't work so they are focusing
on the vaccine not having time to work - or the vaccine protection
not lasting very long.  This possibility was reinforced in 2001 by
the observation that many of the cases in fully vaccinated horses
occurred very close to the time of the second vaccination - with
symptoms showing up anywhere from 24 hours to 12 days or so after the
second shot.  Of the four 2002 cases to end March, 2 had completed
their 2 shot vaccine series four months before, 2 had completed it 60
days before.

About all that's known for sure so far is that the vaccine is not
100% protective.  Don't know how much off 100% it is because we don't
have numbers for how many horses were vaccinated and how many
vaccinated horses were exposed to the virus.  That's why the
challenge studies are needed.  If it works at all, it's not a strong
protection, takes a long time to kick in and is lost very quickly.
For example, if you start the series on June 1st, you have to wait at
least 3 weeks for the second injection and about two weeks after that
for protection - middle of July - and you can only count on it for
about another 60 days.

If the vaccine is actually precipitating signs in some horses, it
wouldn't be the first time.  Many experts advise strongly against
vaccinating horses for the Rhinopneumonitis virus during an outbreak.
The vaccination may precipitate neurological signs in a horse with an
active virus infection.  There is absolutely no proof the West Nile
vaccine may be doing this - just enough circumstantial evidence to
raise a question in my mind.

Eleanor



Message 2

Snip>Message: 4
   Date: Sat, 25 May 2002 11:12:45 -0700
   From: "S. K. McCarthy" <smcc@xxxxxxxxxx>
Subject: West Nile Virus vaccine

Whether it comes from successful hype by Fort Dodge, or from the 
reasonable expectation that the virus will be nationwide in short 
order, horses in my area have been getting vaccinated for West Nile 
Virus even though the virus does not yet exist out here. I am in 
California, and we have all the vectors and required hosts in plenty. 
For good or bad, I have vaccinated several hundred horses with this 
vaccine (including my own) and my colleagues past and present (I 
recently changed practices) have vaccinated at least a thousand or 
two more. This is what I have observed.

The vaccine has been well tolerated in terms of few fevers, sore 
necks, etc that could be attributed to the West Nile vaccine. In many 
cases I was giving other vaccines at the same time, and it is 
difficult to know whether any resulting fever/soreness was from the 
West Nile vaccine or others given simultaneously. As I have had no 
adverse reports when giving the second booster by itself, I am 
inclined to think that the West Nile vaccine was not the culprit in 
earlier reactions. I had one young horse develop a fever about four 
hours after initial vaccination, but this seems a bit soon to be a 
standard vaccine reaction. I had heard anecdotal reports of a couple 
of vaccinated horses having a high GGT, but this has not really 
panned out as far as I know.

More importantly I think I can add info regarding the matter of signs 
of the disease showing up in fully vaccinated horses, and whether 
these signs were in fact caused by the vaccination. In several 
thousand doses administered, in an area where the actual disease DOES 
NOT yet exist, I have seen and heard of no horses showing signs that 
remotely resembled what I have been led to expect with disease from 
West Nile virus. This suggests to me that the Florida horses who 
showed signs of the disease after vaccination either were not 
protected and developed the disease anyway, or the vaccination has 
these effects only in the presence of natural virus.

Keeping in mind that like many diseases, serologic testing indicates 
that the exposure rate to West Nile is far higher than the case rate. 
One has to wonder if some of these horses had already been exposed to 
the virus prior to vaccination without ever having become 
symptomatic. Perhaps the vaccine affects such horses differently?

The harder one looks at the problem, the more complex it gets. 
Certainly the rate of disease in fully vaccinated horses makes me 
wish to reconsider my policies. (I currently recommend vaccination 
but am not remotely dogmatic about it.) If it turns out that more 
doses are necessary to get good protection, then I will look smart 
when the disease gets here and my and my client's horses are 
protected from vaccinating well in advance and probably getting at 
least a third dose in a year after the first series. On the other 
hand, I am going to look pretty stupid if it turns out that the 
vaccination is ineffective and I have been spending my client's money 
on a useless vaccine. All I can do at this point, is try to stay 
current on the information as it emerges, and make the best judgment 
I can. If the vaccine is as safe as it seems so far, then at least 
all I risk is wasted effort and money, rather than the well-being of 
my patients. It certainly gives food for thought.

Sarah McC, DVM




Message 3

Snip>Message: 8
   Date: Sun, 26 May 2002 10:24:28 -0000
   From: "drkellon" <kell@xxxxxxxx>
Subject: Re: West Nile Vaccine

Personally, I would not.  That is strictly my opinion, based on the
information that is (and is not) available to date.  If challenge
studies prove a good immunity, but short-lived, I would vaccinate
intensively but only after testing the horse first to make sure it
has not been exposed.  If challenge studies show both weak immunity
and short immunity, I would not use it.

Eleanor

--- In horsescience@xxxx, PEnglett1@xxxx wrote:
> Eleanor,
>
> The question remains, if you lived in FL would you or would you not
vaccinate
> for WNV?
>
> Phil



Don & Linda Pollock
Badge Motto: Audacter et Strenue 
JR, Bay Star, Rusty and the cats and dogs 
1400 Birdie Road
Lawrenceburg, Ky. 40342
E-Mail to: <donp@xxxxxxx>

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