Reimmunization Increases Contraceptive Effectiveness of ...€¦ · 11/3/2018 · Reimmunization...
Transcript of Reimmunization Increases Contraceptive Effectiveness of ...€¦ · 11/3/2018 · Reimmunization...
Reimmunization Increases Contraceptive
Effectiveness of GonaCon-Equine Vaccine in
Free-Ranging Horses (Equus caballus):
Limitations and Side Effects
Investigators:
D. Baker1, J. Powers2, J. Ransom2, B. McCann2, M. Oehler2,
J.Bruemmer1, N. Galloway2 , D. Eckery3, and T. Nett1
1Colorado State University, 2National Park Service, 3United 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
• Alter native plant communities
• Compete for limited forage resources
• Limited methods of population control
United States Geological Survey
Management Problems:
Overabundant Feral Horses
• Vaccine
• GnRH antibodies
• Inhibits ovulation and spermatogenesis
• Tested in many wildungulate species
• Single treatment –multiple years
• Safe
• EPA approved for feral horses, burros, and white-tailed deer
GnRH Vaccine (GonaCon-Equine)
Ovary
Ovum
Testis
spermatogenesis
Hypothalamus
GnRH
Anterior Pituitary
FSH LH
testosterone
estrogen/progesterone
Reproductive Pathway
Gonads
Brain
ovulation
BLOCK
BLOCK
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
• No difference in maintenance
behaviors (feeding, resting,
travelling)
• No difference in social
behaviors (herding, agonism,
reproductive)
Results: Behavior
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 1st 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
• 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
Acknowledgements:
Questions?