Remotely delivered immunocontraception in free-roaming feral burros (Equus asinus).
Abstract: Regulation of local overpopulations of free-roaming feral equids is in demand worldwide for ecological balance and habitat preservation. Contraceptive vaccines have proven effective in feral horses, which breed seasonally, but no data are available for equids such as the burro, which is reproductively active all year round. In the present study, 27 individually identified female feral burros (Equus asinus) roaming free in Virgin Islands National Park (St John, US Virgin Islands; Lesser Antilles) were remotely treated with pig zonae pellucidae (PZP) vaccine. Between January and May, 16 burros were darted with a 1 ml emulsion of PZP plus Freund's adjuvant. Ten to twelve months later each treated burro was given a single booster injection of PZP plus adjuvant to maintain contraception through a second year. Eleven adult untreated jennies served as controls. Beginning one year after initial vaccination, these burros were monitored for pregnancy and foal production. Collection of data to determine treatment effect was not begun until 12 months after initial treatment to ensure that pregnancies existing before vaccination were not included. Pregnancy was assessed using previously validated methods for steroid metabolite measurement in fresh faecal samples. None of the PZP-treated burros produced foals between 0 and 12 months after the last inoculation. One PZP-treated burro tested positive for pregnancy at 10 months after the final inoculation. During this same period, six of 11 untreated burros tested pregnancy-positive, and four were observed with foals. There was no difference in pregnancy rates among treated, control and randomly sampled jennies between 12 and 24 months after the last inoculation. The results demonstrate that, in free-roaming feral burros that are reproductively active all year round: (1) burros can be accessed for remotely delivered PZP vaccination; (2) PZP contraception is effective; (3) PZP contraception is reversible; and (4) pregnancy can be reliably detected by faecal steroid analysis.
Publication Date: 1996-05-01 PubMed ID: 8699431DOI: 10.1530/jrf.0.1070031Google Scholar: Lookup
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- Journal Article
Summary
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The research paper demonstrates that the introduction of a contraceptive vaccine (PZP) in free-roaming feral burros (donkeys) has proven effective in managing their reproduction and consequent population control. The burros that were vaccinated didn’t produce any foals in the first 12 months following the final inoculation.
Objective of the Study
- The study sought to explore ways to control the overpopulation of feral equids, like burros, which is a requirement for maintaining the ecological balance and preservation of habitat. While contraceptive vaccines have worked on feral horses, there was no data on their efficacy on burros, which are reproductively active throughout the year.
Methods Used in the Research
- The study involved 27 identifiable female feral burros in the Virgin Islands National Park, which were remotely treated with pig zona pellucidae (PZP) vaccine.
- Between January and May, 16 burros were given a dart with a 1 ml emulsion of PZP and Freund’s adjuvant. They also received a booster shot 10-12 months later to maintain contraception for the next year. Eleven adult burros that weren’t treated acted as controls.
- Pregnancy and foal production were monitored a year after the initial vaccination, excluding data collection in the first 12 months to eliminate already pregnant burros before treatment.
- Pregnancy was ascertained using reliable methods for measuring steroid metabolite in fresh faecal samples.
Findings of the Study
- The study showed none of the PZP-treated burros gave birth to foals in the 0-12 months after the last shot.
- One treated burro was found pregnant 10 months after the final shot. In contrast, during the same period, 6 out of 11 untreated burros were confirmed pregnant, with four spotted with foals.
- There was no significant difference in pregnancy rates between treated burros, control group, and randomly sampled burros 12-24 months after the final vaccination.
Conclusion of the Study
- The study confirmed that free-roaming feral burros respond well to remotely administered PZP vaccination for contraception.
- It established the effectiveness of PZP contraception in burros, asserting its successful reversal over time, thus making it a feasible solution for population control of species that are reproductively active throughout the year.
- The research also emphasized the reliability of faecal steroid analysis for pregnancy detection.
Cite This Article
APA
Turner JW, Liu IK, Kirkpatrick JF.
(1996).
Remotely delivered immunocontraception in free-roaming feral burros (Equus asinus).
J Reprod Fertil, 107(1), 31-35.
https://doi.org/10.1530/jrf.0.1070031 Publication
Researcher Affiliations
- Department of Physiology and Molecular Medicine, Medical College of Ohio, Toledo 43699, USA.
MeSH Terms
- Animals
- Animals, Wild
- Contraception, Immunologic / methods
- Contraception, Immunologic / veterinary
- Equidae
- Feces / chemistry
- Female
- Pregnancy
- Pregnancy Tests
- Swine
- Zona Pellucida / immunology
Citations
This article has been cited 5 times.- Massei G. Fertility Control for Wildlife: A European Perspective. Animals (Basel) 2023 Jan 27;13(3).
- French H, Segabinazzi L, Middlebrooks B, Peterson E, Schulman M, Roth R, Crampton M, Conan A, Marchi S, Gilbert T, Knobel D, Bertschinger H. Efficacy and Safety of Native and Recombinant Zona Pellucida Immunocontraceptive Vaccines Formulated with Non-Freund's Adjuvants in Donkeys. Vaccines (Basel) 2022 Nov 24;10(12).
- Gupta SK, Bansal P. Vaccines for immunological control of fertility. Reprod Med Biol 2010 Jun;9(2):61-71.
- Hampton JO, Hyndman TH, Barnes A, Collins T. Is Wildlife Fertility Control Always Humane?. Animals (Basel) 2015 Oct 21;5(4):1047-71.
- Asa CS, Moresco A. Fertility Control in Wildlife: Review of Current Status, Including Novel and Future Technologies. Adv Exp Med Biol 2026;16:605-645.
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