Non-surgical options for canine population control: What's available and what's on the horizon?

Approximately 75% of the world's dog population is stray or feral. These animals can be responsible for nuisance behaviour, predation and ecological threats, in addition to diseases affecting animal production and human health. Currently, euthanasia or fertility control are options commonly used to mitigate feral animal problems. However, due to the perception and reality of euthanasia being unpalatable to most societies, the focus of population control has shifted to management by fertility control. Surgical sterilisation is considered the gold standard for contraception, but is not without its risks, expense and logistical limitations. Therefore, this review will focus on the latest options available for non-surgical contraception in dogs which include hormonal contraceptives (e.g. Gonadotrophin releasing hormone (GnRH) agonists), immunocontraceptives (e.g. vaccines against GnRH, zona pellucida proteins) and male chemical sterilants (zinc gluconate, calcium chloride). Additionally, recent research has targeted fertility control at the molecular level such as targeted gene silencing through RNA interference and anti-kisspeptins. Hopefully, a single dose treatment that will address most of the criteria for an ideal contraceptive including: social acceptance, animal welfare, efficacy, legal compliance, feasibility, and sustainability, will soon be available. However, transition from surgical to non-surgical population control will require support from animal population management stake-holders and government policy.