How many doses of the vaccine are required?
It is absolutely essential that a previously unvaccinated horse receive two doses
of the vaccine at 3-6 week intervals. The equine population in the US has been
virtually naive to this virus until 1999. Therefore, we are starting from "scratch"
in regards to protecting our horses against West Nile virus by vaccination.
What if I exceed the 3-6 week vaccination interval?
Serology data obtained on the vaccine and its immune response was obtained
from horses vaccinated at a 3-6 week interval. We have no serological data
supporting an extended vaccination interval. While one would assume the
horse's immune "memory" would extend beyond that, there has been no
serological testing to support that. While it is the practitioner's discretion,
Fort Dodge Animal Health suggests that horses receive an additional booster
(a 3rd dose) 3-6 weeks after the second booster, if the initial 3-6 week
booster interval has been exceeded.
When can I expect immunity after the second dose of vaccine?
In serological studies, the majority of the horses seroconverted within two weeks
after the booster dose of vaccine. There were some who seroconverted at three
to four weeks. Therefore, it would be ideal to have the first and second dose of
vaccine completed at least one month prior to exposure to the mosquito vectors.
Can I use the West Nile - Innovator vaccine in a pregnant mare?
Currently, the West Nile - Innovator vaccine does not carry a claim for vaccination
of pregnant mares. However, in pre-release safety trials, 32 of 649 horses were
pregnant mares which were closely monitored following vaccination. There were
no ill effects demonstrated in the mares, their pregnancies or their subsequent
foals. Since its release, thousands of doses have been administered to pregnant
mares. A low number of undiagnosed abortions have been reported from the
field following use; these reports appear to be associated with individual animal
responses due to stress, which can occur with any vaccine administered to
pregnant animals. The safety of West Nile - Innovator vaccine is similar to that
of other routinely used killed virus vaccines such as the sleeping sickness
combination products. For additional information contact your veterinarian.
When should I begin vaccinating foals?
Maternal interference and passive transfer studies have yet to be completed
at this time. Once these have been completed, the ideal age for vaccination of
foals will be determined. At this time, the following general recommendations
are being made by many equine practitioners based on experience with
Sleeping Sickness vaccines:
| (1) | In a high risk situation (in regards to potential exposure to the wild virus), foals born from mares not previously vaccinated for West Nile virus may be vaccinated beginning at 6-8 weeks of age, with two doses of vaccine at 3-6 week intervals. If the mares did receive the vaccine prior to foaling, it is recommended starting at 3-4 months of age. | |
| (2) | In low risk areas, foals from vaccinated mares may be started at 5-7 months of age, while foals from non-vaccinated mares can be started at 3-4 months of age. |
totally inactivated, making it a killed-virus vaccine. It would not be possible
for a horse to contract the West Nile Virus from the vaccine. Does my horse need a third dose of the vaccine? According to labeled directions, once a horse is vaccinated with West Nile
virus vaccine (the initial two doses given 3-6 weeks apart), it would thereafter
only require an annual booster. Some veterinarians are recommending more
frequent boostering depending on the level of mosquito and potential viral
challenge to horses in different geographic areas. Check with your veterinarian
and/or state agencies regarding recommended vaccination protocols in your
geographic location. Is the West Nile - Innovator vaccine safe for all breeds of horses? Yes. The West Nile - Innovator vaccine is safe for all breeds of horses. It has
also been used safely in donkeys, mules, and miniature horses, although no
label claim for these animals is approved at this time.