There are a ton of good reasons to spay or neuter your pet. Not only do you help reduce the unwanted pet population, but you lower the risks of certain kinds of cancer and help control some kinds of behavior. Spayed/neutered pets live longer on average than intact ones. But what if someone is afraid of having surgery done on their pets? What about the costs and time involved in "fixing" stray dogs and cats?
Believe it or not, there are other options.
Researchers have been investigating non-surgical options for sterilization, and some are on or close to being on the market. Some are injections and others are implants (similar to certain kinds of human birth-control). Here's a look at a few.
Neutersol--This came on the US market in 2003, but left the market two years later because of a split between the patent holder and the marketing company. It involved a single injection in each testicle that would leave the dog sterile without the need for surgical castration.
EsteriSol (Mexico), Infertile (Brazil)--Like Neutersol, these are intratesticular injections that result in sterility. Right now they are only available in the listed countries.
Gonazon--This product received approval in the European Union in 2006. It is an implant for female dogs and cats, providing long-term birth control by hormonally preventing the estrus (heat) cycle. There is a possibility of the same product being used to control fertility in males.
Suprelorin--Similar to Gonazon, this is a sustained-release implant that suppresses testosterone in male dogs. It was released in Australia and New Zealand in 2004-2005, and is available in some European countries. Though not approved for use in females, some studies have shown the potential for its effectiveness.
Currently these are the only approved products on the market (that I am aware of). And there are several pros and cons. The biggest benefits would be a lower cost than surgery and lower risks. For stray dogs and cats where we only want to try and control reproduction this would be a very helpful option. Many shelters and rescue groups could to more cost-effective "trap and release" programs. However, the implant products only work for a year or so at the most, so repeated dosing would be needed.
The cons revolve around the fact that we spay and neuter for reasons other than reproductive control. Removing the reproductive organs does lower the risks of several kinds of disease and cancer in both genders. Chemical sterilization would not really help with these risks, as the organs are left intact. Depending on the product used, there would also be some hormonal production which could lead to undesired behaviors (such as aggression or marking territory).
Other products are currently in development that would include vaccines against certain reproductive cells and receptors. These have not been approved and have certainly not been perfected.
Personally, I think that the tried-and-true method of surgical sterilization is still the best one for pet owners, as the health risks is low and the benefits are high. You only have to go through the surgery a single time, as opposed to potential recurrent implants and injections with most of the other methods. Still, the idea of a good non-surgical option holds promise, and I agree that it's an area that deserves more research.