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I can't speak for the WNV vaccine specifically, but (Susan and Heidi can
correct me if I'm wrong) there is a risk with certain types of vaccines for a
couple of reasons:
Some animals have an allergic reaction to the serum--some vaccines are
produced in other animal species that can develop an antibody titer to the
causative agent but don't get sick, for example. (Which is why when you go
to get a flu shot they ask you if you react to flu shots or may even ask if you
are specifically allergic to horses--horse serum is involved in its production
somehow.) Or the animal might react to the adjuvant, which if I remember
correctly is a compound used to stimulate antibody titer as well. This is
why the ridiculous trend of slapping a Band-Aid on you when you get a vaccine is
such a stupid one--take them off ASAP! That itching is a local reaction of
your skin to the serum or carrier that leaks out of the injection site.
Second is the type of vaccine...killed or modified live. Killed
vaccines are just that--the virus is dead--it can't invade cells and use the
cell DNA or RNA to multiply. Modified live ones are live but have been
modified with genetic engineering or some other procedure to be less
dangerous. The goal of both is to stimulate the body's immune system to
make antibodies that will recognize and fight the real thing if the animal (or
you) is (are) exposed. If I remember my notes from Diseases (the darn
things are buried in a box somewhere, unfortunately), some animals can develop a
mild form of a disease from some modified live vaccines. Or, in some cases
(such as the human smallpox vaccine) they use a virus that's closely related to
the one which causes the illness, but doesn't make that specific animal
sick. Smallpox vaccine is (or was) made using cowpox--the antibody titer
we build up is effective against smallpox, but cowpox virus doesn't make us sick
because it is species-specific.
So to answer your question directly--the point is to try to develop a
reasonable immunity within the horse population to help slow the spread of
WNV, which isn't species-specific. WNV is one of those diseases that
causes encephalitis, or inflammation of the brain, and like Eastern and Western
Equine Encephalitis, is dangerous for humans. It is also transmitted by a
vector (carrier which isn't affected by the disease but can transmit it), which
means you can get it even if you never come in contact with an infected bird or
horse or whatever. The vector, of course, is the dreaded skeeter.
Animal vaccines can be developed and approved for release much faster than those
for humans, because they are to some extent part of the development process for
human vaccines. So, we vaccinate the animals that are susceptible that we spend
time around to try to reduce the chances that one of
those blood-sucking, needle-nosed pests gets it from the horse and gives it
to us. In this way, it's like vaccinating our animals against rabies--the
goal is to decrease the chances not only of the animals getting a dreadful
disease and suffering/dying, but to protect the human population as well.
Thus ends Dr. Redmond's lecture in Vaccines and Disease
Transmission 101. =)
I freely admit it has been years since I studied this particular topic, so
Susan and Heidi, please correct or add whatever you need to!!!!!!!!!!
Lisa
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