Currently, the most common method of preventing unplanned pregnancies in dogs and cats is removal of the ovaries and uterus in females, and the removal of testicles in males. These procedures can also protect against certain types of cancers and have positive effects on behavior. However, for those involved in animal shelters or rescue, it can be time consuming and costly to neuter a large number of animals in this way.
Is Surgical Neutering a thing of the past?
There are some non-surgical methods of rendering male dogs infertile:
- Zeuterin is an injectable liquid containing zinc gluconate. It is injected into the testes of dogs, where it causes tissue damage. The result is reduced sperm production and blockage of the movement of sperm along the reproductive tract. It has some disadvantages. Vets need to be trained in its use, and it can be uncomfortable for the dog. Some patients develop ulcers at the injection site. In addition, studies suggest that in most dogs, there is no effect on blood testosterone levels so although these dogs are infertile, there are none of the behavioral changes that you'd see with surgical neutering.
- Veterinarians in Italy are exploring ultrasound as a non-invasive way of sterilizing male dogs. It, too, causes damage to testicular tissue and has no effect on testosterone levels.
A new vaccine developed by scientists in Chile looks like it may change how we manage the reproductive ability of domestic pets on a larger scale. The Chilean veterinarians have taken technology that was already available for pig management and adapted it for use in pet dogs. They have developed a vaccine that neutralizes gonadotropin-releasing hormone, which is the key hormone involved in reproductive function. Without this hormone, male dogs and cats produce no testosterone and females no estrogen or progesterone. The result is that they don't come on heat, don't exhibit unwelcome mating behavior and don't produce sperm or eggs. They also aren't at risk of hormone-related health conditions such as mammary cancer or pyometron. Thus, it's a form of immunological neutering.
What about side effects? There are few if any, and would be not unlike what you'd expect to see after surgical neutering. In mature animals, there may be a change in their metabolism that requires an adjustment in food intake. Currently, studies are exploring the effects on orthopedic health of neutering dogs when young. It may be that using such a vaccine in pups could be expected to have the same effect as surgical removal of the source of hormones. The effect of the vaccine is reversible, so boosters will be needed to keep those reproductive hormones at bay.
This vaccine will be a great option for many pets, such as those who can't safely be anesthetized for routine surgery. However, its greatest benefit will be to the shelter population. If shelter veterinarians can effectively neuter cats and dogs quickly and easily, and without the expense of surgical procedures, they will be able to help a larger number of animals for the same cost.