SpayVac Fertility Control Study Begins at Pauls Valley, OK
Posted by Texas Mustang Project on April 27, 2011
(Links and resources at the end of BLM’s Press Release)
Bureau of Land Management
Contacts: Paul McGuire (Oklahoma) (405-794-9624) Heather Emmons (Nevada) (775-384-7966) Tom Gorey (Washington, D.C.) (202-912-7420)
For release: Tuesday, April 26, 2011
BLM, USGS Begin New Wild Horse Fertility Control Study
The Bureau of Land Management and the United States Geological Survey (USGS) have begun a five-year wild horse contraceptive study at the BLM’s short-term holding facility in Pauls Valley, Oklahoma. The pasture breeding study will test the effectiveness of two formulations of the investigational contraceptive vaccine SpayVac® to determine if the treatment can reduce foaling rates in wild horse mares.
The goal is to see if SpayVac®, a novel formulation of a glycoprotein called porcine zona pellucida (PZP), will provide a longer-term effect than other PZP vaccines currently used by the BLM. If the vaccine is found to reduce foaling in this controlled setting, it will be considered for use with free-roaming horses to help control population growth rates on the
As the primary agency responsible for management of wild horses on U.S. public lands, the BLM has a need for a long-lasting contraceptive agent to control herd growth rates. Given the protection afforded by the Wild Free-Roaming Horses and Burros Act of 1971 and a general lack of natural predators, wild horse populations increase at an average rate of 20 percent a year and can quickly exceed the carrying capacity of their ranges.
The BLM, as part of its development of a new wild horse and burro management strategy, has been stepping up its efforts to reduce population growth rates in wild horse herds using contraceptive agents. A main limitation of the agents currently available is that they are of relatively short duration or need to be administered annually. Maximizing the duration of contraceptive effectiveness is especially important in wild horses, which in most cases must be captured in order for the treatment to be successfully administered.
In the BLM-USGS study, 90 mares have been treated with either one of two formulations of the vaccine or a placebo. The mares will be followed for five years to measure anti-PZP antibody levels and compare the foaling rates between treated horses and controls. Although breeding is not usually allowed to occur in BLM facilities, a clinical trial in this controlled environment will provide critical information on how well SpayVac® works as a contraceptive.
The mares and stallions enrolled in the study were selected from horses already in BLM holding facilities. They are being housed in three 30-acre pastures and will be together during the next five breeding seasons. Foals that are born during the study will be offered for adoption each fall after they have been weaned. At the conclusion of the study, all adult horses
will be returned to the BLM’s Adopt-A-Horse Program or placed in long-term pasture facilities.
The BLM has an interagency agreement with the USGS for research and scientific support, and this study is a collaborative effort with scientists from the USGS, veterinarians with the Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS), and TerraMar Environmental Research LLC.
Q – Why doesn’t BLM consider other fertility control agents such as SpayVac or Gonacon?
A – GonaCon™ is an experimental fertility control vaccine. Presently, applications of GnRH are being researched in controlled field studies for potential use as a wildlife management tool for deer. Tests of the GnRH vaccine are ongoing in several states and countries, involving a wide range of wildlife and feral species, including horses. At present, the effectiveness of GonaCon™ as a fertility control agent appears similar to or less than PZP-22 which BLM is currently using, suggesting limited potential for development of an effective longer-lasting fertility control agent.
SpayVac™ is an experimental fertility control vaccine using PZPantigens. A single vaccination with SpayVac™ has maintained a high level of contraception throughout the 4-year Nevada estray horse study. There is no regulatory approval for the management or investigational use of SpayVac™ through EPA or FDA. There is no SpayVac™ available for investigational use and no one is currently making it. Data is not available that describes the impact of SpayVac™ on the behavior and physical health of the mares. SpayVac™ may have potential for use as an effective, longer-lasting fertility control agent in the future. It may also offer an alternative to spaying mares in the future. However, additional research over the next 5-10 years would be needed before it could be used on a population-management basis.
WILD HORSE BIRTH CONTROL WITH PZP from Dianne Nelson of The Wild Horse Sanctuary, Shingletown, CA
A Similar Vaccine, American Herds Blog Post, October 02, 2010