Use of anti-gonadotropin-releasing hormone vaccines in African elephants (Loxodonta africana) : a review

Abstract

BACKGROUND : Androgen-related aggressive behaviour and musth cause serious problems in captive African elephant bulls and often lead to human and animal injuries, and damage to property. OBJECTIVES : To review the work carried out with anti-gonadotropin-releasing hormone (GnRH) vaccines to control androgen-related behaviour and fertility in captive and free-ranging elephant bulls and the induction of anoestrus in elephant cows. METHOD : In the first study, an anti-GnRH vaccine from Pepscan was tested in six bulls (four captive and two free-ranging). Once the vaccine Improvac® became available, the effect on behaviour, the reproductive organs and semen quality was tested. Improvac® was also used to attempt induction of anoestrus in elephant cows. RESULTS : The first study proved that aggressive behaviours are significantly associated with increased faecal androgen concentrations. Musth (n = 1) and aggressive behaviour (n = 2) were down regulated and correlated with a decline in faecal androgen concentrations. Aggression and musth could be controlled with Improvac® (600 μg), but were more consistent when the dose was increased to 1000 μg administered every five to six months. The same dose down regulated testicular function and bulls (n = 17) were rendered infertile within 12 months after commencement of treatment. Initial attempts to induce anoestrous with 600 μg in free-ranging elephant cows gave inconclusive results, but 1000 μg in captive cows delivered five-monthly was successful. CONCLUSION : The treatment of elephant bulls with Improvac® resulted in the successful downregulation of androgen-related behaviour and sperm production in captive and wild elephant bulls of various ages (≤ 34 years). Preliminary studies to induce anoestrus in cows with Improvac® appear to be successful.