January 15, 2024: 

AWHC’s Internal Science Committee has conducted an extensive review and analysis of the scientific literature on the use of the GonaCon immunocontraceptive vaccine in wild horses and burros. 

Based on this review, AWHC concludes that there is insufficient data on the vaccine’s efficacy, reversibility, potential side effects, and darting feasibility to justify its use as a management tool for federally-protected herds at this time. 

We believe PZP vaccines offer numerous advantages over GonaCon, including scientifically documented efficacy, reversibility, and a less complex protocol for darting that better ensures successful inoculation. Further, the impacts of PZP on wild horse herds are well documented, while the impacts of GonaCon have received extremely limited scientific attention, with no long-term data available.

For this reason, AWHC does not support the use of GonaCon in wild horses or burros beyond limited, tightly controlled research settings. 

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