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

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 down-regulation 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.