Originally published by Animals 24-7

WASHINGTON D.C.––Friends of Animals on May 20, 2015 asked the U.S. Environmental Protection Agency to “consider new scientific evidence demonstrating the need to cancel the registration of porcine zona pellucida (PZP) for population control of America’s wild horses and burros, which was issued to the Humane Society of the United States in 2012,” the FoA cover letter to EPA chief administrator Gina McCarthy said.

HSUS won registration of a PZP-based immunosterilant called ZonaStat-H, developed for use in controlling wild horse and burro populations, in January 2012,   after a three-year application process.

 Requirements waived

Summarized FoA Wildlife Law Program legal director Michael Harris, “HSUS requested waivers for most of the studies ordinarily required from an applicant seeking a pesticide registration, including a toxicity study, ecological effects and environmental fate guideline study, and an efficacy study. The requested waivers were granted.

HSUS “was allowed to seek its registration based on several studies conducted in the 1990s.” Harris continued, “regarding the efficacy of the drug as a wild horse and burro contraceptive. These studies conclude overall that PZP can be highly effective at reducing fertility rates among wild horses with little to no side effect. A majority of these reviews were published by Jay Kirkpatrick, a veterinarian who manufactures PZP for use on wild horses.”

Claims side-effects were not considered

HSUS and Kirkpatrick, Harris charged, “did not consider the biological, social and behavioral effects the drug can have on wild horses.”

Since ZonaStat-H won EPA approval, Harris said, “PZP has been in widespread use. For example, the Bureau of Land Management, which has jurisdiction over the largest number of wild horse herds on federal public lands, has administered approximately 1,944 doses of PZP to wild mares.  The U.S. Forest Service has used PZP on mares in the Carson National Forest and potentially elsewhere. The use of contraception generally, and the use of PZP specifically, is advocated by the U.S. Geological Survey and the National Academy of Science.”

Argued Harris on behalf of FoA, “Research has now demonstrated changes in mare stress and reproductive physiology, in addition to changes in male behavior,” allegedly resulting from use of PZP.

“For example,” Harris said, “researchers now know that PZP poses the risk of immediate physical damage to the dosed mares, can increase the mortality rate in foals born to treated mares after the PZP loses its effectiveness, can result in social disruptions among herds with treated mares that can damage long-term herd cohesion that is critical to the health of the animals, and places the wild horses at risk of a genetic bottleneck.

“Although the information regarding PZP used to support its registration is generally accurate regarding PZP efficacy,” Harris allowed, “with regards to ecological and environmental effects it is outdated now.”

Read the full article on the Animals 24-7 website.