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Answers to
Frequently Asked Questions About Wildlife Applications for SpayVac
How does SpayVac™ work?
The antigens in SpayVac™, porcine (pig) zona pellucida (PZP) proteins,
cause a treated female mammal to produce antibodies that adhere to the surface (zona
pellucida) of her own ova (eggs) and prevent sperm from binding, thus
blocking fertilization.
What is SpayVac™ composed of?
SpayVac™ is made up of three components: the antigen (PZP extracted and purified
from pigs ovaries), liposomes (cholesterol and lecithin), and an adjuvant, to
stimulate the immune response. Except for the PZP antigen, all other components
have been previously approved in other vaccines. However, PZP has been
incorporated into research vaccines for >20 years.
Does SpayVac™ affect the well-being of treated animals?
Because SpayVac™ results only in antibodies that block sperm binding, the
effects on treated animals are minimal. The largest changes relate to the fact
that most treated animals will not become pregnant, and in some species (e.g.,
White-tailed Deer), repeated estrous cycles result in repeated matings. The
result may be an extended breeding period and increased mating activity.
Increased longevity of treated wild horses has been also been reported. PZP
vaccines have been used in wildlife and zoo animals for about 20 years and are
generally regarded as safe.
Is SpayVac™ environmentally safe?
Unlike hormone contraceptives, which can find their way into the food chain, PZP
protein antigens and the resulting antibodies are harmless to the environment.
PZP antigens and antibodies are digested like any other proteins by humans,
predators, scavengers, and microbes.
How much experience is there with SpayVac™?
SpayVac™ was developed in the early 1990s by scientists from Dalhousie
University in Halifax, Nova Scotia, Canada. It was first tested on several
species of seals, and much experimental work was conducted using laboratory
rabbits. In Grey Seals, SpayVac™ has provided contraception for at least 10
years. In 3-year studies of Fallow Deer and White-tailed Deer, SpayVac™ has been
100 % effective. Studies involving Domestic Cats, Barbary Sheep, Horses, Grizzly
Bears, and Wolves are underway or have been concluded. Over the past 20 years,
conventional PZP vaccines have been tried successfully in many other mammalian
species. [For a complete account of the Fallow Deer study, see Fraker et al.
2002. Long-lasting, single-dose immunocontraception of feral fallow deer in
British Columbia. Journal of Wildlife Management 66(4):1141-1147.].
How often do treated individuals have to be inoculated to
maintain contraception?
In long-term experiments with Grey Seals, SpayVac™ has been effective for at
least 10 years with only a single inoculation. SpayVac™ has been 100% effective
for 3 years in both Fallow and White-tailed Deer. Experiments with other species
have not yet extended beyond 1 year. We expect that SpayVac™ will have
multi-year effectiveness in many species of mammal, but the exact duration
probably will vary according to species. Only testing for many years can
accurately assess effective duration.
Is there any particular time of year when SpayVac™ should be
administered?
SpayVac™ can be administered whenever fieldwork is most conveniently conducted
and when animals can be captured easily and safely. For example, with deer,
capture and treatment should not occur immediately prior to fawning, when does
and their unborn fawns might be especially vulnerable to injury, nor in the few
weeks following fawning, when dependent fawns might become separated from their
dams. At present, our limited experience suggests that antibody titers should
rise to contraceptive levels within about 60 days post treatment. Thus, if it is
hoped that deer are to be effectively contracepted before a particular rutting
season, they should be inoculated at least 60 days prior.
What is the difference between SpayVac™ and conventional PZP
vaccines?
Conventional vaccines use PZP proteins (antigens) and an adjuvant (immune
response stimulant). SpayVac™ uses exactly the same antigens and often the same
adjuvant as do conventional vaccines. The critical difference is that the PZP
proteins in SpayVac™ are encapsulated in liposomes, which protect them while
they are being carried to the immune system. Liposomes have been used for many
years and are recognized as safe components of therapeutics.
In
practical terms, the most important difference between SpayVac™ and the
conventional PZP vaccine is performance. SpayVac™ is the only vaccine to achieve
multi-year contraception with just one administration. The conventional vaccine
initially requires a primary inoculation followed by 1 or 2 boosters within a
few weeks, with annual boosters afterwards. Although the conventional vaccine
has been used in trials on deer at a number of locations, the need to hold
animals for extended periods to administer initial boosters (or relocate and
“dart” free-ranging animals) and to administer annual boosters makes the
conventional vaccine generally impractical.
Because only a single administration is required, SpayVac™ will be much less
expensive to use than conventional vaccines and will involve much less stress
for treated animals. The greatest expense in implementing fertility control is
incurred for catching and holding animals. Each capture treatment involves
stress and a risk of injury to both animals and workers.
What is an adjuvant and which adjuvant is used in SpayVac™?
Adjuvants are materials that are incorporated into vaccines to enhance the
immune response. Trials of the conventional PZP vaccines have routinely used
Freund’s Complete Adjuvant (FCA), which is recognized as the “gold standard” of
adjuvants and is used widely in vaccine research. FCA has also been used in
trials of SpayVac™. Although FCA is a very powerful adjuvant, some individual
animals may respond adversely, and vaccines containing FCA cannot obtain
regulatory approval. Fortunately, SpayVac™ performs well with another adjuvant,
AdjuVac, which has regulatory approval. Although we may continue to use FCA for
research, other adjuvants, with regulatory approval, such as AdjuVac, would be
used in SpayVac™ formulations intended for routine use.
Are
there limitations to using SpayVac™ to manage wildlife fertility?
Yes. For the foreseeable future, it will be practical to treat only small
populations that are isolated and accessible. The present state-of-the-art
requires that all treated animals be captured and marked before being treated,
and this will be difficult to achieve in many situations. By itself,
contraception cannot quickly reduce the size of a population of concern.
Must
SpayVac™-treated animals be marked? How?
In most cases, Yes, with at least ear tags and often with marking collars or
radio collars, tattoos, and/or microchip tags, which are methods that are
routinely and safely used in wildlife research. In field use, the primary reason
for this is to avoid treating the same individuals more than once, which would
expose animals to potential injury from darts or other capture methods. In areas
where hunting occurs, marking animals would allow hunters to discriminate
between treated and untreated animals. While SpayVac™ is undergoing scientific
trials, positive identification of individual animals is also necessary.
Can
SpayVac™ be safely administered to pregnant animals?
Yes. SpayVac™-elicited antibodies affect only unfertilized eggs. There is no
effect on pregnancies already in progress.
Does
SpayVac™ have any effect on the DNA of treated animals?
No. As with any other immune response, there is no effect on the genes of
treated animals.
Does
SpayVac™ works on males as well as on females?
No. SpayVac™ will elicit antibody production in males, but because males do not
have ovaries, they do not possess eggs or zona pellucida proteins. Thus
SpayVac™ has no useful effect on males.
How
much does SpayVac™ cost?
At present, SpayVac™ is not in commercial production and a price has not yet
been set. However, the most expensive part of any wildlife contraception program
is securing the animals to be treated, and because SpayVac™ requires only a
single administration, overall costs will be much less than those involved with
the conventional vaccine.
How
can I obtain SpayVac™ for use on deer or other wildlife in my area?
The responsibility for wildlife management generally rests with state or
provincial wildlife agencies. Thus, an early step should be to consult with the
appropriate people within the responsible management agency. If there is a
desire to try SpayVac™, this may be possible under the provisions for field
trials contained in Food and Drug Administration (FDA) rules in the USA, Health
Canada rules in Canada, or the rules of the appropriate agency elsewhere.
ImmunoVaccine
Technologies Inc. (IVT), Halifax, Nova Scotia, Canada, is commercializing
SpayVac™ for use on companion animals and wildlife. TerraMar Environmental
Research Ltd., Sidney, BC, Canada, is the “strategic partner” with IVT for
research and development of SpayVac™ for wildlife applications.
When
will SpayVac™ be commercially available?
In early 2003, SpayVac™-for-Wildlife, Inc., a not-for-profit corporation, was
formed in Princeton, New Jersey. Its primary purposes are to:
1. Take
SpayVac™-for-Deer through the regulatory process of the US Food and Drug
Administration, and
2. Produce
and market SpayVac™-for-Deer at low cost
Meeting the
regulatory requirements will require an investment of perhaps as much as US$5
million. Because the estimated market is small, SpayVac™-for-Wildlife, Inc., is
seeking charitable contributions to cover the regulatory-approval costs.
The time
required before SpayVac™-for-Deer will be commercially available will depend to
a large degree on the availability of funds to accomplish various tasks. Under
favorable conditions, SpayVac™-for-Deer could be on the market by 2008.
SpayVac™-for-Wildlife,
Inc., can be contacted through its President, Mark Fraker (250-656-3972) or its
Vice-President, Robert Cervelli (902-492-1819).
On
what species has SpayVac™ been tested?
The following species have been tested as of May 2001: Fallow Deer (Dama dama),
White-tailed Deer (Odocoileus virginianus), Black-tailed Deer (Odocoileus
hemionus columbianus), Horses (Equus caballus), Barbary Sheep (Ammotragus
lervia), Grizzly Bears (Ursus arctos), Wolves (Canis lupus),
Grey Seals (Halichoerus grypus), Hooded Seals (Cystophora cristata),
Harp Seals (Phoca groenlandica), and Laboratory Rabbits (Oryctolagus
cuniculus).
Who can I
contact for more information?
Wildlife Applications:
Mark A. Fraker, President
SpayVac™-for-Wildlife, Inc. and
TerraMar Environmental Research Ltd.
Sidney, British Columbia, Canada
tel:
250-656-3972 fax: 250-656-3474 e-mail
maf@spayvac.org
SpayVac™ Product Information:
Robert Cervelli, Vice-President
SpayVac™-for-Wildlife, Inc. and
ImmunoVaccine Technologies Inc.
Halifax, Nova Scotia, Canada
tel:
902-492-1819 fax:902-492-0888 e-mail: rlc@spayvac.org
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