Non-Surgical Sterilization

Animal overpopulation concerns in communities around the world are a regular topic at Urban Animal events as industry stakeholders strive to find a humane, efficient, cost-effective and sustainable solution. To help us better understand some of the emerging trends, Dr. Drew Van Niekerk examines alternatives to costly spay/neuter procedures. 

Overpopulation of cats and dogs has been a problem around the world for decades.  Differences of opinion about controlling roaming and sterilization, as well as urban population explosions have all contributed to the growing numbers of reproducing stray dogs and cats. Surgical sterilization of females using ovariohysterectomy (spay) or of males using castration (neuter) have been promoted and utilized in attempts to control unwanted litters as well as community overpopulation. True cost of these procedures has been subsidized by private veterinarians for years, or completed at spay/neuter clinics in an assembly line fashion, all in an attempt to reduce reproducing adult numbers in our communities. In some regions, this has had a profound impact, but many regions are hopelessly outnumbered and unable to make a sustainable dent in the populations. The cost of these programs is considerable, making pragmatic efforts difficult.

There is no shortage of proposed solutions to this problem.

Veterinarians from TuftsUniversity’s Cummings School of Veterinary Medicine have offered a different perspective on the issue, proposing vasectomies and hysterectomies may be superior because of the downward effect on reproduction rates seen in the preservation of hormonally driven behavior in a population.

“Sex drive and social status would remain intact, allowing males to protect turf from other feral males, ward off new strays, and compete for females, which go into a prolonged state of “nonreceptive” pseudo-pregnancy after sexual activity. Females likewise continue to compete with sexually functional females. The result: fewer successful matings, the researchers conclude.” 

While more information and data is certainly needed, some have argued that simply vasectomizing may not offer the solution. The Alliance forContraception in Dogs and Cats   has been searching for a permanent non-surgical sterilization solution for 14 years. 

The ACC+D, founded in 2000 out of Auburn University, proposes non-surgical solutions would be potentially less expensive, and easier to administer, issues key to the success of the future of population control. They propose the following priorities:

Priorities for Non-Surgical Products for Pet Population Control 


1. Approved by regulatory agencies as safe (for animals and for the humans administering) and effective.

2. Permanent, though there may be some opportunity for long-term (3+ years) products. 

3. Deliverable in a single injection or treatment. 

4. Products available for effective use in both male and female, dogs and cats. Documented effects on behavior and health.
5. Can be provided at affordable rates for use in indigent or low-income client populations.

An Ontario Veterinary College researcher has received a $260,000 grant in support of research aimed at developing an inexpensive, non-surgical alternative for sterilizing shelter animals.

Based out of Bragg Creek, Alberta veterinarian, Dr. Judith Samson-French has been trialing the use of injectable ‘deslorelin’, a GnRH agonist on First Nations female dog populations, with some success. “We have been importing the drug, routinely used in Australia, using the Emergency Drug Release program,” she said. Dr. Samson-French has been observing sterility for approximately 3 years. “We need to go after the females” expanding that to impact a population through sterilization of the males, likely requires over 90% of the population to be sterilized."

Zeuterin™ (U.S.) is a product developed to permanently chemically sterilize male dogs through a process called "zinc neutering." It is marketed outside the U.S. under the label EsterilSol™. This intratesticular injection is effective, but has adverse reactions such as swelling, redness and irritation and requires anti-inflammatory pain killers, creating a logistical problem to administer in free roaming dog populations.

Dr. Samson-French feels we are ten years away from a permanent non-surgical injectable sterilization product for females, citing not only the lack of a current available product, but an expensive, lengthy and arduous regulatory approvals process.

Veterinary specialist Dr. Julie Levy, Maddie’s^® Professor of Shelter Medicine
Director, Maddie’s^® Shelter Medicine Program at the University of Florida has been studying a vaccine for GnRH, called Gonacon.

The study showed 93% effectiveness against fertility for 1 year, and a drop to 50% efficacy in 3 years, and 27% in 5 years.

The work continues to discover the solution to overpopulation, and research into novel innovations such as nonsurgical contraception provides hope for the Animal Industry and communities around the world.

Dr. Drew Van Niekerk celebrates more than 20 years in the Urban Animal Industry as a practicing veterinarian in Calgary, Alberta and a long-standing board member of the Calgary Humane Society. Drew is also a staunch supporter of Urban Animal Program events and the initiatives and conversations that arise from them.