Abstract: The Humane Society United States (HSUS) has been partnering with several prominent researchers for over 20 years to assess the potential use of Porcine Zona Pellucida (PZP), a protein used as a fertility control vaccine for wild horses. Past studies on herds located on barrier islands of the eastern United States have demonstrated that PZP prevented pregnancies and was a valuable tool for population management. With the generous support of the Annenberg Foundation and in partnership with the Science and Conservation Center, Tufts University and The University of Toledo, HSUS is conducting a 5-year longitudinal study to assess the effectiveness of immunocontraception on over 600 wild horses in the western United States.
This project involves 2 herds of over 300 wild horses each located in Utah and Colorado. We began gathering pre treatment data in April 2008. Birth rates, band size, and individual horse identifications were recorded. In the winter of 2008/2009 both herds will be captured and all mares that are released will be treated with a 2-year-duration PZP vaccine. Both herds will be closely monitored for reproduction and behavior changes for 3 years. We will record the differences in reproductive success of treated and untreated (not captured) females.
HSUS is also seeking to develop refinements to the PZP vaccine and delivery technologies. HSUS is currently trying to improve the production of the PZP vaccine by producing it with techniques that are more efficient and less costly. Improving delivery methods for the 2 year drug is another goal of this research that may allow herd managers the flexibility of treating mares year round without having to capture it. HSUS also hopes to demonstrate that incorporating this new delivery method and proactively managing wild horse herds will assist in maintaining wild horse populations at a level that is sustainable and manageable.