Wildlife Contraception: Targeting the Oocyte

The USDA’s National Wildlife Research Center (NWRC) has successfully researched and developed a number of chemical and immunologically-based wildlife contraceptives. DiazaconTM interferes with cholesterol metabolism and disrupts steroidogenesis, while nicarbazin (registered as OvoControl-P and OvoControl-G) disrupts the structure of the vitelline membrane of bird eggs. Immunologically-based agents act to stimulate targeted antibody production. GonaConTM causes the host’s immune system to bind gonadotropin releasing hormone, preventing ovulation, while SpayVacTM prevents fertilization of the postovulatory oocyte. This kind of target specificity can be highly advantageous. A number of oocyte-only control contraceptive strategies are currently being researched at the NWRC. 4-Vinylcyclohexene diepoxide (VCD) is an industrial chemical which is specifically ovotoxic, depleting the ovarian oocyte pool with repeated exposure. Research into VCD efficacy as well as the comparability of a similar diepoxide, ERL 4221, in rats and pigs is in progress. Immunological inhibition of recently discovered oocyte-secreted proteins which regulate follicular development in mammals is also of interest. Two such proteins, growth differentiation factor 9 (GDF9) and bone morphogenic protein 15 (BMP15), are highly specific targets for the suppression or elimination of folliculogenesis. These oocyte-specific strategies may offer new, effective alternatives for wildlife contraception.