Announcing a new contraceptive method:
The AZA Wildlife Contraception Center at the Saint Louis Zoo and The Contraception Advisory Group in collaboration with The ZooPharm Division of Wildlife Pharmaceuticals announce a new contraceptive method: Leuprolide injectable for remote delivery. Leuprolide, a gonadotropin-releasing hormone (GnRH) agonist, has been formulated in a controlled-release system that can be delivered by dart. Once injected, the special polymer forms a biodegradable implant. The release-system can be modified to alter release dynamics, allowing for hormone delivery from 30 days up to 6 months.
Leuprolide effects contraception by temporarily suppressing the reproductive endocrine system, preventing production of pituitary (LH and FSH) and gonadal hormones (estradiol and progesterone in females and testosterone in males). The observed effects are similar to those following ovariectomy or castration, but are reversed after the hormone content of the implant is depleted.
As a hormone agonist, leuprolide is initially stimulatory, causing estrus and ovulation in females or enhancing testosterone output and sperm production in males. Following the initial stimulation, the reproductive system is down-regulated.
As with deslorelin, this method can be used in a wide variety of females, but may not be adequate for male ungulates nor some marsupials. Efficacy in females can be monitored with estrous behavior or gonadal steroids in serum or feces. Efficacy in males may correlate with testosterone suppression, but documentation of absence of sperm may be more important when used as a contraceptive. Once spermatogenesis is interrupted, it may take several weeks or months until there are no more viable sperm in the ejaculate (similar to vasectomy).
Trials to date have focused mainly in captive female cervids (Wapiti (Cervus elaphus nelsoni), Baker et. al., 2002; Mule deer (Odocoileus hemionus), Baker et. al., 2004). No adverse effects were detected during these investigations. In both species, all females were suppressed for one breeding season, and reproductive function was fully restored the next season.
Baker, DL, MA Wild, MM Conner, HB Ravivarapu, RL Dunn, TM Nett. 2002. Effects of GnRH agonist (leuprolide) on reproduction and behavior in female wapiti (Cervus elaphus nelsoni). Reproduction (supp.) 60:155-167.
Baker, DL, MA Wild, MM Conner, HB Ravivarapu, RL Dunn, TM Nett. 2004. Gonadotropin-releasing hormone agonist: A new approach to reversible contraception in female deer. J Wildlife Diseases 40(4): 713-724.