Efficacy of dart-delivered PZP-22 immunocontraceptive vaccine in wild horses (Equus caballus) in baited traps in New Mexico, USA
Kathleen A. Carey
A , Alexa Ortiz A , Kayla Grams B , Dan Elkins C , John W. Turner A Center for Animals and Public Policy, Cummings School of Veterinary Medicine, Tufts University, 200 Westboro Road, North Grafton, MA 01536, USA.
B Humane Society of the United States, 700 Professional Drive, Gaithersburg, MD 20879, USA.
C Mt Taylor Mustangs, PO Box 2946, Santa Fe, NM 87504, USA.
D Department of Physiology and Pharmacology, University of Toledo College of Medicine, 3035 Arlington Avenue, Toledo, OH 43614, USA.
E Corresponding author. Email: allen.rutberg@tufts.edu
Wildlife Research 46(8) 713-718 https://doi.org/10.1071/WR18112
Submitted: 9 July 2018 Accepted: 17 August 2019 Published: 9 December 2019
Abstract
Context: Federally protected wild horses on public lands are undergoing population growth that overwhelms the historical management strategy of removal and adoption. Porcine zona pellucida (PZP) has been used as an injectable immunocontraceptive vaccine to induce reversible infertility in free-roaming horses. PZP vaccination during February and March, which is the optimal time for administering current vaccines, is not possible for the herd on Jarita Mesa Wild Horse Territory (JM WHT), New Mexico, due to severe weather, terrain and subject wariness.
Aims: The first goal was to assess bait trapping and remote darting as a minimally disruptive alternative to helicopter gathers for treatment. The second goal was to quantify the efficacy over 2 years following spring treatment with a single injection of PZP-22 (a combination of PZP-adjuvant emulsion and controlled-release pellets) by remote dart delivery.
Methods: Bait trapping and dart delivery of PZP-22 was carried out on JM WHT from 4 April to 16 June 2012. The herd was observed in the summers of 2011, 2013 and 2014 to determine the foaling status of the study mares. Outcome (foal or no foal) as a function of treatment was analysed using Fisher’s exact test.
Key results: There were 157 individuals, including 66 females >1 year old, documented in 2011. In 2012, 26 females (including three yearlings) identified by colour and markings were bait trapped and darted with PZP-22. The proportion of treated females foaling was lower than that of untreated females in 2013 and 2014, but the difference was only significant in 2013. Of the treated mares observed in 2013, the two that foaled were the last two treated in 2012. Untreated mares >4 years old were significantly more likely to foal than younger mares.
Conclusions: Bait trapping at JM WHT permitted successful delivery of PZP-22 in a previously inaccessible herd. Dart administration of PZP-22 in April–June induced at least 1 year of measurable infertility.
Implications: This is the first demonstration of the efficacy of an initial treatment of PZP-22 delivered by dart instead of hand injection. Considerations for PZP-22 treatment include seasonal timing of treatments and age of treated mares. Treatments need to take place early enough to allow antibody titers to build to contraceptive levels before the breeding season.
Additional keywords: contraception, fertility control, management strategies, natural resource management, population control, population management, reproductive biology, wildlife management.
References
Baker, D. L., Powers, J. G., Ransom, J. I., McCann, B. E., Oehler, M. W., Bruemmer, J. E., Galloway, N. L., Eckery, D. C., and Nett, T. M. (2018). Reimmunization increases contraceptive effectiveness of gonadotropin-releasing hormone vaccine (GonaCon–Equine) in free-ranging horses (Equus caballus): limitations and side effects. PLoS One 13, e0201570.| Reimmunization increases contraceptive effectiveness of gonadotropin-releasing hormone vaccine (GonaCon–Equine) in free-ranging horses (Equus caballus): limitations and side effects.Crossref | GoogleScholarGoogle Scholar | 30063758PubMed |
Bartholow, J. (2007). Economic benefit of fertility control in wild horse populations. The Journal of Wildlife Management 71, 2811–2819.
| Economic benefit of fertility control in wild horse populations.Crossref | GoogleScholarGoogle Scholar |
Bechert, U. A., and Fraker, M. A. (2018). Twenty years of SpayVac® research: potential implications for regulating feral horse and burro populations in the United States. Human–Wildlife Interactions 12, 117–130.
Bechert, U., Bartell, J., Kutzler, M., Menino, A., Bildfell, R., Anderson, M., and Fraker, M. (2013). Effects of two porcine zona pellucida immunocontraceptive vaccines on ovarian activity in horses. The Journal of Wildlife Management 77, 1386–1400.
| Effects of two porcine zona pellucida immunocontraceptive vaccines on ovarian activity in horses.Crossref | GoogleScholarGoogle Scholar |
Garrott, R. A. (2018). Wild horse demography: implications for sustainable management within economic constraints. Human–Wildlife Interactions 12, 46–57.
Garrott, R. A., and Oli, M. K. (2013). A critical crossroad for BLM’s wild horse program. Science 341, 847–848.
| A critical crossroad for BLM’s wild horse program.Crossref | GoogleScholarGoogle Scholar | 23970685PubMed |
Hobbs, R. J., and Hinds, L. A. (2018). Could current fertility control methods be effective for landscape-scale management of populations of wild horses (Equus caballus) in Australia? Wildlife Research 45, 195–207.
| Could current fertility control methods be effective for landscape-scale management of populations of wild horses (Equus caballus) in Australia?Crossref | GoogleScholarGoogle Scholar |
Killian, G., Thain, D., Diehl, N. K., Rhyan, J., and Miller, L. (2008). Four-year contraception rates of mares treated with single-injection porcine zona pellucida and GnRH vaccines and intrauterine devices. Wildlife Research 35, 531–539.
| Four-year contraception rates of mares treated with single-injection porcine zona pellucida and GnRH vaccines and intrauterine devices.Crossref | GoogleScholarGoogle Scholar |
Kirkpatrick, J. F., and Turner, J. W. (1991a). Compensatory reproduction in feral horses. The Journal of Wildlife Management 55, 649–652.
| Compensatory reproduction in feral horses.Crossref | GoogleScholarGoogle Scholar |
Kirkpatrick, J. F., and Turner, J. W. (1991b). Reversible contraception in nondomestic animals. Journal of Zoo and Wildlife Medicine 22, 392–408.
Kirkpatrick, J. F., Liu, I. K. M., and Turner, J. W. (1990). Remotely-delivered immunocontraception in feral horses. Wildlife Society Bulletin 18, 326–330.
Kirkpatrick, J. F., Lyda, R. O., and Frank, K. M. (2011). Contraceptive vaccines for wildlife: a review. American Journal of Reproductive Immunology 66, 40–50.
| Contraceptive vaccines for wildlife: a review.Crossref | GoogleScholarGoogle Scholar | 21501279PubMed |
Liu, I. K. M., Bernoco, M., and Feldman, M. (1989). Contraception in mares heteroimmunized with porcine zonae pellucidae. Journal of Reproduction and Fertility 85, 19–29.
| Contraception in mares heteroimmunized with porcine zonae pellucidae.Crossref | GoogleScholarGoogle Scholar |
Liu, I. K. M., Turner, J. W., Van Leeuwen, E. M. G., Flanagan, D. R., Hedrick, J. L., Murata, K., Lane, V. M., and Morales-Levy, M. P. (2005). Persistence of anti-zonae pellucidae antibodies following a single inoculation of porcine zonae pellucidae in the domestic equine. Reproduction 129, 181–190.
| Persistence of anti-zonae pellucidae antibodies following a single inoculation of porcine zonae pellucidae in the domestic equine.Crossref | GoogleScholarGoogle Scholar |
National Research Council (2013). ‘Using Science to Improve the BLM Wild Horse and Burro Program: A Way Forward.’ (The National Academies Press: Washington, DC.)
Naugle, R., and Grams, K. (2013). Long-term methods and effects of remotely treating wildlife with immunocontraception. Journal of Zoo and Wildlife Medicine 44, S138–S140.
| Long-term methods and effects of remotely treating wildlife with immunocontraception.Crossref | GoogleScholarGoogle Scholar | 24437095PubMed |
Norris, K. A. (2018). A review of contemporary U.S. wild horse and burro management policies relative to desired management outcomes. Human–Wildlife Interactions 12, 18–30.
Ransom, J. I., Roelle, J. E., Cade, B. S., Coates-Markle, L., and Kane, A. J. (2011). Foaling rates in feral horses treated with the immunocontraceptive porcine zona pellucida. Wildlife Society Bulletin 35, 343–352.
| Foaling rates in feral horses treated with the immunocontraceptive porcine zona pellucida.Crossref | GoogleScholarGoogle Scholar |
Roelle, J. E., Germane, S. S., Kane, A. J., and Cade, B. S. (2017). Efficacy of SpayVac® as a contraceptive in feral horses. Wildlife Society Bulletin 41, 107–115.
| Efficacy of SpayVac® as a contraceptive in feral horses.Crossref | GoogleScholarGoogle Scholar |
Rutberg, A. T., Grams, K., Turner, J. W., and Hopkins, H. (2017). Contraceptive efficacy of priming and boosting doses of controlled-release PZP in wild horses. Wildlife Research 44, 174–181.
| Contraceptive efficacy of priming and boosting doses of controlled-release PZP in wild horses.Crossref | GoogleScholarGoogle Scholar |
Turner, A., and Kirkpatrick, J. F. (2002). Effects of immunocontraception on population, longevity and body condition in wild mares (Equus caballus). Reproduction Supplement 60, 187–195.
Turner, J. W., and Rutberg, A. T. (2013). From the pens to the field: real-world wildlife contraception. Journal of Zoo and Wildlife Medicine 44, S102–S110.
| From the pens to the field: real-world wildlife contraception.Crossref | GoogleScholarGoogle Scholar | 24437090PubMed |
Turner, J. W., Liu, I. K. M., Rutberg, A. T., and Kirkpatrick, J. F. (1997). Immunocontraception limits foal production in free-roaming feral horses in Nevada. The Journal of Wildlife Management 61, 873–880.
| Immunocontraception limits foal production in free-roaming feral horses in Nevada.Crossref | GoogleScholarGoogle Scholar |
Turner, J. W., Liu, I. K. M., Flanagan, D. R., Rutberg, A. T., and Kirkpatrick, J. F. (2001). Immunocontraception in feral horses: one inoculation provides one year of infertility. The Journal of Wildlife Management 65, 235–241.
| Immunocontraception in feral horses: one inoculation provides one year of infertility.Crossref | GoogleScholarGoogle Scholar |
Turner, J. W., Liu, I. K. M., Flanagan, D. R., Bynum, K. S., and Rutberg, A. T. (2002). Porcine zona pellucida (PZP) immunocontraception of wild horses (Equus caballus) in Nevada: a 10 year study. Reproduction Supplement 60, 177–186.
Turner, J. W., Liu, I. K. M., Flanagan, D. R., Rutberg, A. T., and Kirkpatrick, J. F. (2007). Immunocontraception in wild horses: one inoculation provides two years of infertility. The Journal of Wildlife Management 71, 662–667.
| Immunocontraception in wild horses: one inoculation provides two years of infertility.Crossref | GoogleScholarGoogle Scholar |
U.S. Forest Service (2006). Environmental Assessment for wild free-roaming horse management on the El Rito Ranger District. USDA Carson National Forest, Albuquerque, NM.
U.S. Geological Survey (2013). About WHIMS. USGS, Fort Collins Science Center, Fort Collins, CO. Available at http://www.fort.usgs.gov/resources/spotlight/horse/whims.asp [verified 16 September 2013].
