Immunocontraception of male and female giraffes using the GnRH vaccine Improvac®

Abstract

The aim of this study was to develop protocols for contraception in both sexes of giraffes ( Giraffa camelopardalis) by using the GnRH vaccine Improvac®. We evaluated the success of immunization by analyzing fecal reproductive hormone metabolites in female ( n = 20) and male ( n = 9) giraffes. Endocrine analysis provided the basis for the successful immunization protocol, as well as for assessing long‐term effects. Reliable reduction of fecal steroid metabolites to baseline levels in female giraffes was achieved with three, and in males with four or five injections at 4‐week intervals. Effective booster injections were administered at 2‐month intervals in the first year of treatment and at three to 4‐month intervals in the following years. In addition to endocrine analysis, we determined vaccination efficacy in bulls by assessing testicular atrophy. Long‐term (>2 years) use in females was often accompanied by prolonged periods of persistent corpus luteum activity, although normal cycles were not observed. Problems might occur with reversibility, because in a few males and females, even after more than 2 years since treatment had been stopped, fecal hormone metabolites have not returned to pretreatment levels. The results are somewhat ambiguous, as reproduction can be suppressed by use of Improvac®, but the question of reversibility remains unsolved.

Abstract

I Protocols for contraception using the GnRH vaccine Improvac® were developed. A clear reduction of fecal hormone metabolites in female giraffes was achieved with three, and in males with four or five injections at 4‐week intervals. Effective booster injections were administered at 2‐month intervals in the first, and at three to 4‐month intervals in the following years.

RESEARCH HIGHLIGHTS

• Contraceptive efficacy of Improvac® treatment was achieved in both, female and male giraffes.

• Fecal hormone metabolite analysis was used for establishing an effective contraception via vaccination.

• The recommended protocol comprises three Improvac® injections in female and four or five injections in male giraffes, each to be administered at 4‐week intervals. After this basic immunization, booster injections should be given at 2‐month intervals during the first year of treatment and at 3‐ to 4‐month intervals in the following years. These immunization protocols lead to reliable suppression of fecal reproductive steroid hormone metabolites.

• Vaccination success in males can be monitored by observing testicular atrophy.

• Reversibility remains questionable.