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Immunocontraception
In 1988, a
new approach to wildlife contraception was launched. Immunocontraception
is based on the same principles as disease prevention through
vaccination. We vaccinate ourselves and other animals against
diseases by injecting dead or attenuated (weakened) disease
bacteria or viruses, or molecules which are harmless but similar
to the toxins that these disease organisms produce. Our immune
systems produce antibodies that attack the material we injected
and any similar organism or their toxins in our systems. An
immunocontraceptive vaccine works in much the same way, only
it causes the production of antibodies against some essential
event or structure in the reproductive process. There are
a variety of immunocontraceptive vaccines under development,
including vaccines against brain reproductive hormones such
as gonadotropin-releasing hormone (GnRH); pituitary hormones
such as luteinizing hormone (LH), follicle-stimulating hormone
(FSH); vaccines against steroid reproductive hormones such
as estrogen and progesterone; and vaccines against the sperm
and the egg, which in turn prevent fertilization. The advantages
of vaccines are that they can be delivered in very small doses,
and because they are primarily protein, they are readily destroyed
in digestion and cannot pass through the food chain. The vaccine
which thus far has had the largest application to wildlife
is the Porcine Zona Pellucida, or PZP vaccine.
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