Rabbit Advocacy Animal Matters


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: