Wild Horse Fertility Control Group (WHFGC)

PZP Immuno-Contraceptive Vaccine

- the best tool currently available for the humane management of Alberta's wild horses

If we have a humane population management solution at our disposal why wouldn't we make use of it? Why would we resort to culls?

What is PZP?

Porcine Zona Pellucida (PZP)
Porcine Zona Pellucida (PZP) is an immunocontraceptive that is used to control the reproductive rate of some mammalian species, including horses, deer and elephants. It has been in use since the 1980’s. PZP (porcine zona pellucida) is a protein that occurs naturally in pig ovaries. Zona pellucida (ZP) proteins surround the unfertilized eggs of all mammals. Sperm must attach to ZP before an egg can be fertilized. When pig ZP (PZP) is injected into a female animal, her body produces antibodies to it. These antibodies attach to her own ZP proteins, preventing sperm from attaching and blocking fertilization. When injected into a female mammal this foreign protein induces an immune response that results in the generation of antibodies to combat the protein. Some of these antibodies attach to the sperm receptors on the zona pellucida of the target animal’s eggs and thereby prevent fertilization.
Types of PZP
There are two primary types of PZP for use on wild horses:

ZonaStat-H – The Science and Conservation Center in Billings, Montana manufactures ZonaStat-H, otherwise known as “native PZP.” It is the product used by the Wild Horses of Alberta Society to treat horses in part of the Sundre Equine Zone.

PZP-22 – Is comprised of a combination of native PZP and PZP that is incorporated into lactide-glycolide pellets that are designed to dissolve in the host’s body slowly over time. It contains both a primer and booster dose. It was called PZP-22 in the hope that it would provide at least 22 months of contraception with a single injection.
Has PZP Been Used in Canada?
In 2014 the Wild Horses of Alberta Society entered into a five year Memorandum of Understanding to dart horses in a 400 sq. km. portion of the Sundre Equine Zone. Between 2015 and 2017 they darted approximately 90 horses by free range field darting. The future of this program, which ends in October 2019, is unclear at the present time. In the meantime the Government of Alberta has indicated that they will entertain serious proposals from other groups to conduct similar programs in areas of high concern.
How is PZP Administered?
Free-Range Field-Darting: Dart delivery systems for free-range field darting vary considerably and can include rifles and pistols that may be CO2 or cartridge powered. Typically, the range for accurate free-range darting is within about 50 meters of a wild horse. Here is a picture of a CO2 dart gun with rifled barrel. We would suggest adding a mounted laser scope, range finder and a GoPro camera to video the shot.

image Capture-Dart-Release: Horses may be baited into corrals and PZP can be delivered by jab stick or from a dart gun suitable for close range darting. Delivery by close range dart gun is preferable to and less invasive than hand injection where the horses have to be run through a chute and handled. It may also be the most effective method in more remote and densely populated areas.

Heli-Darting:WHFGC does not support heli-darting at this time and there is currently no information available to show that it would be a viable option in the Alberta foothills.
Who Manufactures PZP?
The ZonaStat-H form of PZP is manufactured by the Science and Conservation Center in Billings, Montana.
What is the Cost of PZP?
The cost of a single dose of PZP plus adjuvant (a substance that enhances the body's immune response to an antigen) and a non-reusable dart is approximately CAN$75.

"We believe that PZP is the best tool available. ....any side effects (real, perceived or hyped) pale in comparison to the negative impacts imposed by round-up and removal strategies."

Wild Horses of America Foundation

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