Skip Links

USGS - science for a changing world

Scientific Investigations Report 2009–5038

Prepared in cooperation with the Bureau of Land Management

Injection-Site Reactions in Wild Horses (Equus caballus) Receiving an Immunocontraceptive Vaccine

By James E. Roelle and Jason I. Ransom

Abstract

Thumbnail of and link to report PDF (6.8 MB)

The U.S. Geological Survey and the Bureau of Land Management are conducting research on the efficacy of the immunocontraceptive agent porcine zona pellucida (PZP) in reducing fertility of wild horses (Equus caballus). As an antigen, PZP stimulates antibody production when injected into many mammalian species. These antibodies bind to the external surface of the ovum, preventing fertilization. By itself, PZP is only weakly immunogenic and is therefore delivered with an adjuvant, most commonly one of the Freund adjuvants, designed to further stimulate antibody production. Freund’s complete adjuvant (FCA) in particular is known to be very effective, but may also be associated with undesirable side effects such as formation of abscesses at injection sites. Such reactions may be exacerbated when accompanied by the additional trauma of a remotely delivered dart. Because horses in our three study herds were individually identifiable by color markings and harem association, we were able to monitor mares for injection-site reactions (abscesses, nodules, swelling, and stiffness) following inoculation with PZP.

In 100 injections delivered by hand we observed a single nodule, two instances of swelling, and no other reactions. In two herds that received remotely delivered (dart) injections, the frequency of reactions was about 1 and 6 percent for abscesses, 25 percent for nodules (both herds), 11 and 33 percent for swelling, and 1 and 12 percent for stiffness. Abscesses were too infrequent to allow meaningful analysis of the relation to covariates, but for the other types of reactions we used logistic regression to examine the relation of occurrence to the delivery method (rifle or CO2-powered blowgun), adjuvant (FCA, Freund’s modified adjuvant, and Freund’s incomplete adjuvant), dart trauma (normal or abnormal), and age of mare. Abnormal dart trauma included cases where the dart hit bone or the needle broke off. We found strong evidence (odds ratio = 5.023, P = 0.001) for a higher probability of occurrence of swelling when darts were delivered by blowgun. We found some evidence (odds ratio = 8.729, P = 0.07) that abnormal dart trauma led to a higher frequency of nodule formation. Nodules were the most common reactions observed and often persisted for a year or more, but in our observations they did not appear to change any animal’s range of movement or locomotor patterns and in most cases did not appear to differ in magnitude from naturally occurring injuries or scars. We were unable to perform histological examinations of these nodules, but they may be similar to granulomas reported by other investigators following administration of Freund’s adjuvant.

First posted February 27, 2009

For additional information contact:

Center Director, USGS Fort Collins Science Center
2150 Centre Ave., Bldg. C
Fort Collins, CO 80526-8118

http://www.fort.usgs.gov/

Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.


Suggested citation:

Roelle, J.E., and Ransom, J.I., 2009, Injection-site Reactions in Wild Horses (Equus caballus) Receiving an Immunocontraceptive Vaccine: U.S. Geological Survey Scientific Investigations Report 2009–5038, 15 p.



Contents

Abstract

Introduction

Study Areas

Methods

Results

Discussion

Conclusion

Acknowledgments

References Cited

Accessibility FOIA Privacy Policies and Notices

USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: https://pubs.usgs.gov/sir/2009/5038/
Page Contact Information: Contact USGS
Page Last Modified: Thursday, January 10, 2013, 07:24:36 PM