Treatment with the immunocontraceptive vaccine, GonaCon, induces temporary fertility control in free-ranging prairie dog populations in Colorado, USA

Abstract

Context Prairie dogs (Cynomys spp.) are rodents enjoyed by some humans; yet, they cause crop and property damage, and carry zoonotic disease. Non-lethal control of prairie dogs is of interest in urban/suburban settings. The injectable immunocontraceptive vaccine GonaCon (active ingredient is gonadotropin-releasing hormone [GnRH]) has been shown to be effective at reducing fertility in equine and deer, and is a US EPA-registered vaccine for use in these ungulate species. Aims To conduct a replicated field study to test efficacy of GonaCon in black-tailed prairie dogs (C. ludovicianus), and if found to be efficacious, to help facilitate the EPA registration of this product for prairie dog management in urban/suburban areas. Methods Prairie dogs were live-trapped in October–December 2018 in three treatment and three control sites. Every captured female ≥660 g was injected with 0.4 mL of either GonaCon (0.032% w/w GnRH) at treatment sites or a sham vaccine (absent of GnRH) at control sites. Juveniles and adults were counted at all six sites to establish juvenile:adult (ratio) and juvenile density in May–June 2019 (determining initial GonaCon effectiveness) and 2020 (determining persistence of contraception). Key results In 2019, the juvenile:adult ratio was significantly reduced (P = 0.0022) in GonaCon (mean ± s.e.: 0.23 ± 0.01) relative to the sham (1.10 ± 0.58) sites. Juvenile density was three times greater in sham than GonaCon sites. In 2020, GonaCon sites produced equal offspring to nearby sham sites. Conclusions GonaCon is highly effective during the first year (2019) but not in the second year (2020) if only a small area (0.6–2.8 ha) or small proportion of females in a colony is treated, such as was undertaken in this study. Implications In 2022, GonaCon−Prairie Dogs was EPA-registered. Treating whole colonies of prairie dogs at once is favoured; yet, if small or partial colony treatment is desired, then annual GonaCon treatment may be needed.

Foreword to the Special Issue on ‘Fertility control for wildlife in the 21st century’

“…Studies on GonaCon presented at the conference focused on the use of this vaccine to manage populations of freeroaming cattle (Bos taurus/Bos indicus) in Hong Kong (Massei et al 2015b(Massei et al , 2018Pinkham et al 2022 (Shiels et al 2024) included in this Special Issue was conducted on black-tailed prairie dogs (C. ludovicianus) in areas where this native keystone species is associated with zoonotic disease transmission and crop and property damage. These animals live in colonies in urban and suburban settings and their presence and persistence in these landscapes is welcomed by conservationists and citizens that often oppose the use of lethal population control methods to mitigate the impacts of prairie dogs.…”