I went equine vaccine shopping this year, I found there were two choices that
allowed me to combine West Nile Virus with the usual WEE, EEE and Tetanus booster.
in preloaded syringe (RTU)
Requiring Reconstitution (VRR)
(Note that these
acronyms just make things easier to talk about.)
RTUs and VRRs are given intramuscularly (IM) using the provided syringe and 1
½ long 20 gauge needle.
that are ready-to-use, requiring no reconstitution, come as a preloaded syringe
with a rubber plug and a separate needle that you attach to the syringe prior
to administering. This is a relatively newer, user-friendly type of vaccine that
has been available to horse owners for about 10 years.
year RTUs are available in several combinations such as:
Nile + Eastern and Western Equine Encephalomyelitis (EEE and WEE)
Nile + Eastern, Western, and Venezuelan Encephalomyelitis
Nile + Eastern, Western, and Venezuelan Encephalomyelitis + Tetanus
Requiring Reconstitution (VRR)
Vaccines that need
to be reconstituted are nothing new. In fact, this was about the only way to purchase
equine vaccines prior to the advent of the RTU type described above.
are comprised of a 3 part kit: one glass bottle of dried vaccine powder (in this
case West Nile Virus Live Canarypox Vector), one bottle of liquid diluent (in
this case Killed WEE, EEE and Tetanus diluent), and one syringe with needle.
the syringe and needle, the diluent is drawn out of the bottle and injected into
the bottle containing the dried vaccine. The mixture is shaken until thoroughly
mixed. The mixture is drawn out of the bottle with the needle and administered
to the horse.
- Disadvantages - Potential Problems
use a fairly foolproof procedure but the vet tech that sold the vaccines said
that the following problems could occur so she reminds people to:
forget to add the diluent to the dry mixture. (She said horseowners administer
the diluent only, then call and ask how they can give the dry portion after the
fact ? you cant !!)
- Mix thoroughly
- if there is inadequate mixing, particles could clog the needle or the product
wont dissipate correctly in the horse's tissues.
within 20 minutes of reconstitution or risk less efficacy.
sure to use the correct diluent. If you have more pharmaceuticals in your barn
refrigerator, be sure you dont grab the epinephrine or something else by
the vaccines requiring reconstitution were $3 per head less expensive and because
I am familiar with using that method, I purchased the vaccines requiring reconstitution.
If you have a large number of horses, consider RTU to save time, and consider
VRR to save money. Both types are available in single dose and multiple dose vials.
Multiple dose vials are always less expensive per head. As always, confer with
One or Two West
Although WEE, EEE and Tetanus
boosters are given once a year, it is often suggested that in areas with early
and long mosquito seasons or a high incidence of West Nile Virus, a booster should
be given 3-4 months after the first vaccination in the spring.
the RTU vaccine, it was suggested I purchase two for each horse, one to use early
in the mosquito season and one later in the summer or early fall as a booster.
the VRR, it was not suggested that I purchase two for each horse - one inoculation
is supposed to keep the horses titer up high enough during the entire mosquito
season. The technology behind that vaccine product is supposed to produce a stronger
and longer lasting reaction in the horse.
here at 7000 feet in semi-arid Colorado, we dont see mosquitoes until late
in the summer if at all, so I vaccinate in May or June and that is thought to
be sufficient to protect them through the end of mosquito season. If you are in
other locations, you might vaccinate in March and again in summer or early fall.
Confer with your veterinarian.