Re: Report of Horse Death, possibly resulting from WNV Equine Vaccine

<x-charset iso-8859-1>The serology results and necropsy findings show the mare was already
infected with West Nile virus at the time of the vaccination. I am no great
fan of this vaccine but it would be difficult to "prove" the vaccination
caused the mare to become clinical. Manufacturer would be likely to argue
it could be totally coincidental (i.e. the timing of the appearance of
symptoms) and/or that nonspecific stress, such as the transport, may have
contributed to her becoming symptomatic.

However, the advisability of vaccination for any disease in the face of an
outbreak has always been a point of debate. Does the further "challenge" or
"burden" to the immune system from a vaccination "weaken" or "stress" the
host so that disease becomes more likely? Can any vaccination have this
effect, or is it worse if you vaccinate for the disease the horse is already
incubating (? possibly interfering with antibodies by tying them up with
vaccine antigen, or causing an exaggerated inflammatory/immune response by
the load of vaccine antigen)? It could also make a difference whether this
is an immunologically naieve horse, seeing the infection for the first time,
or whether this is an agent to which the animal has previously been exposed,
in which case the antibody response would be more rapid. On the other hand,
repeated doses of vaccine are sometimes used in the treatment of a disease
(e.g. rabies, and some vets are using the EPM vaccine in this way).

I have cross-posted this message (but without the identifying information)
to another, "vets only", list, and asked for comments on the above issue of
vaccination in the face of an outbreak also. If I get any feedback, will
let you know.

I can almost guarantee that what you are likely to be told is that the horse
was already infected and it was the infection, not the vaccine, that killed
her. Also likely to be told that X million doses of vaccine have been used
on horses in endemic areas, etc.. with no proof it is dangerous, although
the fact is there is no proof it is safe to vaccinate an already infected
horse either. Although I cannot give you absolute numbers, I can tell you
this isn't the first time a horse has developed acute symptoms of West Nile
within a short period of time (1 to 10 days) following either first or
second vaccination. Coincidence? Vaccine risk? We don't know. However,
it is VERY, VERY IMPORTANT that this case be reported to the USDA as a
possible vaccine reaction. Nothing can be done about investigating the
possibility, or issuing appropriate warnings, if they are unaware of it.
You do not have to be a veterinarian to report a suspected vaccine reaction.
Go to:
http://www.aphis.usda.gov/vs/cvb/ic/adverseeventreport.htm for a clear and
concise description of the reporting process, and to:
https://web01.aphis.usda.gov/CVB/adverseeventreport.nsf/Adverse%20Event%20Re
port%20Form?OpenForm, to access the form itself.

Eleanor Kellon, V.M.D.

----- Original Message -----
From: Environmental Risk Analysis Program <envrisk@cornell.edu>
To: WESTNILEVIRUS-L <WESTNILEVIRUS-L@cornell.edu>
Cc: Pursley, David <dpursley@mgmt.purdue.edu>; <rkeene@fdah.com>
Sent: Tuesday, October 22, 2002 12:05 PM
Subject: Report of Horse Death, possibly resulting from WNV Equine Vaccine

> Hello, my name is CPT David M. Pursley, located in Indiana. My horse
> died on September 9th after receiving immunizations for WNV, EPM, and
> Potomoc fever. On September 5th we trailered our two apparently
> healthy arabian mares with no signs of WNV to the vets for
> immunizations. Upon return home, approximately one hour after
> immunizations, my five-year-old mare began to stumble and displayed a
> sore neck (the locations of the shots). A few hours later the mare's
> front left leg became partially paralyzed and she had trouble
> standing. The vet was called to the house to check for signs of a
> reaction to the drugs and she administered Dexamethasone, Banamine
> and took a serology. The next morning the mare showed no signs of
> improvement and became worse. A few hours later the mare had no motor
> control of her front legs and became recumbent. The vet returned and
> administered a catheter and my family and I began life support
> measures for the next four days to include IVs with Dex, and Banamine
> injections. The horse was conscious, able to nibble hay and drink
> water when we could support her head up. She would have spasmadic
> convulsions and would attempt to get up but her front end was
> paralyzed. Her rear legs would kick and retained motor control. She
> had no urine or bowel movements the entire time. She appeared
> hydrated and alert with slight edema. It was a traumatic experience
> for my family and our beloved mare of significant value with a
> championship pedigree that we had high hopes for. We took our mare in
> for preventive measures and she subsequently died.
> The serology that was drawn the evening of the immunizations returned
> positive for WNV. A postmortem exam was conducted by Purdue
> University and a description of Histopathology follows:
> Brain: The primary lesions in the sections examined were those of
> multifocal non-suppurative encephalitis. Mulitfocally, large numbers
> of venules both in gray and white matter which had prominent
> endothelium contained moderate numbers of lymphocytes and a few
> macrophages in the Virchow-Robin space. The neuropil exhibited
> presence of scattered inflammatory cells predominantly lymphocytes.
> Also present were a few glial nodules.
> Spinal Cord: The pimary lesions in the representative sections of
> cervical and thoracic segments of the spinal cord were those of
> multifocal non-suppurative myelitis. Multifocally, large numbers of
> venules both in gray and white matter which had prominent endothelium
> contained moderate numbers of lymphocytes and a few macrophages in
> the Virchow-Robin space. The neuropil exhibited presence of scattered
> inflammatory cells predominantly lymphocytes. Also present were a few
> glial nodules.
> Stomach: The section had focal area of erosion. The tuncia mucosa
> focally had superficial loss of epithelium, with mild infiltration of
> neutrophils and hemorrhages in the adjacent area. Most likely caused
> by the stress of being recumbent for four days.
> No gross lesions were observed in the cervical vertebral column or
> spinal cord. The National Veterinary Services Lab report did a PCR:
> Reverse transcriptase polymerase chain reaction (RT-PCR) test
> specific for WNV and eastern encephalitis (EEE) virus on the
> submitted samples. Results: The sample submitted was positive for WN
> viral RNA and was negative for EEE viral RNA. The mare tested
> negative for rabies.
>
> In my humble opinion, The Fort Dodge conditional vaccine caused an
> acute hypersensitive reaction in my mare that led to her death. My
> mare was healthy and accustomed to training and trailing. Based on
> the IgM antibodies, the mare may have had WNV prior to receiving the
> Fort Dodge vaccine but exhibited no symptoms and would most likely be
> alive today if not for the vaccine.
>
> Please advise the general public of these circumstances and provide
> any guidance to me on how to proceed with Fort Dodge.
>
> Respectfully, Dave
> phone:765.491.2231

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Received on Wed Oct 23 11:22:11 2002