Reimmunization Increases Contraceptive Effectiveness of GonaCon-Equine Vaccine in Free-Ranging Horses (Equus caballus): Limitations and Side Effects Investigators: D. Baker 1, J. Powers 2, J. Ransom 2, B. McCann 2, M. Oehler 2, J.Bruemmer 1, N. Galloway 2, D. Eckery 3, and T. Nett 1 1 Colorado State University, 2 National Park Service, 3 United States Department of Agriculture/ Animal and Plant Health Inspection Service
Study Area Southwestern North Dakota 46,000 acres fenced 130 horses 15 bands Historical demonstration herd
Theodore Roosevelt National Park Diverse Badlands typography Multiple wild ungulate species Abundant year-round forage Few predators
Management Problems: Overabundant Feral Horses Alter native plant communities Compete for limited forage resources Limited methods of population control United States Geological Survey
GnRH Vaccine (GonaCon-Equine) Reproductive Pathway Vaccine Hypothalamus Brain GnRH antibodies Ovary Ovum BLOCK GnRH Anterior Pituitary FSH LH Testis testosterone Gonads spermatogenesis BLOCK ovulation estrogen/progesterone Inhibits ovulation and spermatogenesis Tested in many wild ungulate species Single treatment multiple years Safe EPA approved for feral horses, burros, and white-tailed deer
Objective To determine the effective duration and safety of a single vaccination and subsequent reimmunization with GonaCon-Equine in free-ranging horses
Methods: Animal Capturing and Handling
Experimental Horses 2009 (October): Primary Vaccination 29 GonaCon-Equine; 28 saline Similar in age, pregnancy status, stage of gestation, body condition, general health 2013 (September): Reimmunization 4 years post-primary Same mares recaptured and processed 25 GonaCon-Equine; 26 saline control Similar in pregnancy status, stage of gestation, body condition, and general health
Methods: Reproduction Foaling Proportions: Weekly observations of each study mare for presence or absence of a foal during March 1- August 1 each year Vaccine Effectiveness: Vaccine effectiveness as the proportionate reduction in foaling between control and treated mares.
Scan sampling time budgets All-occurrence social behaviors Ransom et al. 2014 Methods: Behavior
Methods: Injection Site Reactions
Results: Reproduction
Results: Behavior No difference in maintenance behaviors (feeding, resting, travelling) No difference in social behaviors (herding, agonism, reproductive)
Results: Injection Site Reactions ~70% swelling or abscess following a single vaccination ~50% similar reactions following reimmunization No evidence of lameness, or depression, was observed for any treated mare following either vaccination
Conclusions: GonaCon-Equine was demonstrated to be safe but minimally effective (30%) and short duration (2 yrs.) when administered as a single inoculation to free-ranging horses. However, when the primary vaccination was followed by a booster immunization, four years later, it was shown to be highly effective (90%) and long-term (4 yrs.) without significant adverse side effects. Management implications?
Future Research: 1. Continue to monitor duration of effectiveness, return to fertility, and effects on the phenology of parturition 2. Continue to monitor the long-term side-effects of reimmunization on treated females 3. Develop and test remote dart delivery of vaccine 4. Determine the most effective reimmunization schedule 5. Conduct population level studies
Reimmunization Schedule? Objective: Determine the optimum interval between the primary and booster immunization. Hypothesis: Decreasing the interval between the primary and booster immunization will decrease effective duration of GonaCon-Equine. Experimental design: Years after 1 st vaccination: 4 2 1 0.5 Sample size: 25 11 15 15 Requires remote dart delivery of GonaCon-Equine Measure: foaling proportions, injection site reactions, body condition
Acknowledgements: National Park Service Animal Reproduction and Biotechnology Laboratory, Colorado State University Bureau of Land Management Morris Animal Foundation National Wildlife Research Center Deb Carson Photography Field Research Technicians and Volunteers the unsung heroes
Questions?