Eyewitness Report: NAS Webinar on SpayVac

January 14, 2016

AWHC Contributor

The National Academy of Sciences (NAS) recently held a public webinar on SpayVac, an immunocontraception vaccine, as part of their review of the Bureau of Land Management's (BLM's) Wild Horse and Burro Program. Dr. Mark Fraker from TerraMar Research Ltd. presented SpayVac, a PZP-based vaccine aimed at long-term fertility control in wildlife. Despite its promising potential, the webinar raised significant concerns about its application in wild horses.

About SpayVac

SpayVac is a formulation of PZP (porcine zona pellucida) designed for single-treatment, long-lasting fertility control. Initially used on gray seals in Canada, it has been tested on various wildlife, including wild horses in Nevada. Dr. Fraker highlighted the BLM as a potential major customer, but panel questions revealed undisclosed issues and serious concerns.

Permanent Infertility?

Dr. Fraker admitted that long-term studies on SpayVac's potential as a permanent sterilant are lacking. A decade-long study on gray seals showed only 10% returned to fertility, while in Nevada, only 2 of 12 mares regained fertility after four years. Dr. Irwin Liu, an NAS panel consultant, expressed concerns about the vaccine's self-boostering effect, which could lead to perpetual infertility.

Side Effects and Behavioral Impacts

Dr. Liu also raised concerns about excessive reproductive tract edema observed in mares post-vaccination, which could lead to infections. Dr. David Thain, an NAS panel member, acknowledged the unexpected frequency of mares in heat, suggesting the need for further studies to understand these effects.

Moving Forward

Dr. Fraker mentioned that SpayVac's registration with the Environmental Protection Agency (EPA) depends on market demand. He assured that the company could meet BLM's potential demand for the vaccine.

Conclusion

While native PZP has been extensively studied and used, SpayVac's application in wild horses remains questionable due to potential side effects and permanent sterilization risks. The NAS webinar reinforced American Wild Horse Conservation's (formerly American Wild Horse Campaign) opposition to SpayVac, emphasizing the need for more research before considering its use in wild horse management.