Reproduction Index Glossary

Nonsurgical Sterilization of Dogs and Cats

The high cost of surgical sterilization will probably always limit its role as a method of pet population control, particularly in non-affluent parts of the world. Additionally, some people view such surgeries as unaccepable infringements on animal rights.

It is clear that an inexpensive and non-surgical method for permanent contraception would be of enormous benefit. A variety of approaches to this goal have been explored, but to date, none have shown sufficient efficacy to be widely deployed.

Injectable Chemical Sterilization

Several investigators have explored injection of irritating chemicals into the testes or epididymides to sterilize dogs and cats. Epididymal injection of such compounds as chlorhexidine gluconate, dilute formaldehyde or zinc tannate have, at times, appeared a promising approach to sterilization. However, when larger scale trials were performed, sterility was not consistently achieved and a significant number of animals developed unsatisfactory inflammatory reactions at the site of injection. This technique is rarely used.

Intratesticular and intraepididymal injection of zinc gluconate neutralized with arginine has shown greater promise than other chemical sterilants, and has been marketed for chemical castration of young dogs (Neutersol). This technique has been shown to be highly effective in eliminating fertility in dogs. However, it does not dramatically reduce secretion of testosterone from the testes, and therefore does not afford the beneficial effects seen with castration. Additionally, sterilizing young male dogs using this technique has not provided substantial cost savings over surgical castration.

Antifertility Vaccines

Several studies have been conducted to evaluate immunization against LH (luteinizing hormone) as a method for contraception or sterilization. By using potent adjuvants, such vaccines were effective in some dogs. In general, however, the level and duration of immunity obtained was so variable that LH vaccines have not been pursued. Similar approaches to immunize against gonadotropin-releasing hormone have also failed to achieve effective contraception.

A large amount of research has been expended to develop vaccines against zona pellucida proteins, and some of this work has focused on dogs and cats. The idea is that antibodies to the zona pellucida may inpair oocyte development, impair ovulation or block binding of sperm to the zona pellucida; any of these effects could reduce or abolish fertility. The image to the right shows pig oocytes that have been stained with a fluorescently-tagged control versus anti-zona pellucida antibodies - the bright fluorescence of the two oocytes on the right is due to binding of anti-zona pellucida antibodies.

To date, an effective zona pellucida vaccine for pets has not been announced, and some studies have demonstrated significant side effects (e.g. development of cystic ovaries) after such treatment of dogs.

Index of: Animal Population Control
Surgical Sterilization of Dogs and Cats Contraceptives for Dogs and Cats

Last updated on April 25, 2006
Author: R. Bowen
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