Those of us familiar with daytime game shows on television will fondly recall Bob Barker ending each episode of The Price Is Right by telling the audience to have their house pets spayed or neutered. He typically prefaced this admonition with the rationale that doing so helps control the pet population. Millions of pets are euthanized every year, so population management is a good reason, of course, to have your female dog spayed. However, it is far from the only one of consequence.
There is a popular truism that still gets trotted out on occasion. It’s the one in which a single unspayed female dog and her similarly unfixed progeny, left to their own devices, can produce 67,000 new dogs within six years’ time. This is a problem with broad generalizations based in geometric progressions: They’re fun and startling thought experiments, but surely if it were true, dogs would have occupied every habitable space on the planet by now.
Why should you get your female dog spayed? Here are three horrifying actual conditions that can happen to female dogs as they age when they are allowed to remain intact:
What is known in humans as breast cancer disproportionately affects intact female dogs; the numbers are alarming, and easier to wrap one’s head around than the thought of a world overrun by unchecked breeding habits. According to the Veterinary Society of Surgical Oncology, between 23 and 34 percent of intact female dogs will develop a mammary tumor. There are a couple of major kinds of growths, also known as neoplasms — classified as malignant and benign — that afflict the mammary glands of female dogs as they reach seniority.
While the specific and actual causes of benign mammary gland tumors and malignant cancers remain unknown, there is clear evidence of a link between the growth of mammary gland tumors and hormones produced during a female dog’s estrous cycle. Mammary tumors in female dogs seem to require the presence of sex hormones to begin growing, though they are no longer necessary once the tumor is there. These tumors can affect any major part of the mammary gland, from connective tissues that link the glands to the milk ducts to the areas around each gland.
Malignant tumors can easily spread. Female dogs have between eight and 10 mammary glands, so an aggressive breast cancer in an unspayed female dog can be a death sentence anytime, particularly between 5 and 10 years of age. The standard spaying procedure — the ovariohysterectomy — before a dog’s first estrous cycle or heat practically eliminates the risk of mammary tumors.
Far less common than mammary tumors but more common than tumors in any of a female dog’s other reproductive organs — the uterus and ovaries especially — perianal fistulas are another health issue that early spaying can help to avoid. Like mammary tumors, perianal fistulae tend to affect female dogs as they age and are seen most frequently in dogs over 7 years of age.
What is a perianal fistula? Also known as a perianal furunculosis, it is a condition in which an abnormal linkage or tunnel is formed between two sets of tissues in the area around the anus. A female dog with perianal furunculosis can have difficulty defecating, but that is only the tip of the iceberg. The unnaturally connected tissues form small holes around the anus which easily grow, expand, leak, and become infected.
Essentially, these fistulae are perpetually oozing, bleeding, and horrid-smelling. They require medical treatment to resolve, from antibiotics and antiseptics to radical dietary changes and surgery, including tail removal in some cases. For those who do not spay their female dogs because of the cost of the procedure, it is a pittance compared to the cost of treating a perianal fistula. Dogs who are spayed have a reduced risk of developing this condition in late life.
Pyometra is by far the most common outcome, exceeding both mammary tumors and perianal fistulae, of leaving a female dog intact. It is also the easiest to prevent by having your dog spayed. What is pyometra? Put simply, it is a condition in which pus accumulates within the uterus. Secondary infections that arise when a female dog develops pyometra are even more dangerous to her health and requires immediate care to prevent death.
How does all this get started? In the standard estrous cycle, white blood cells do not enter the uterus while the organ’s lining thickens to prepare for pregnancy. If there is no pregnancy, that lining is not sloughed off and excreted, as in the human menstrual cycle, but absorbed over time back into the body. After several consecutive estrous cycles without a pregnancy, cysts can begin to form in what remains of the uterine lining. If the cervix closes and bacteria are present in the uterus, the infection can take hold.
Most cases of pyometra begin within eight weeks of the end of an estrus cycle, and the severity of the condition depends on whether her cervix is open or closed. Closed pyometra has been likened to appendicitis in humans, and can become life-threatening with little warning. Open pyometra, when the cervix remains open, is easier to detect; like perianal fistula, it is accompanied by noticeable leakages. Pus will become more visible, draining from the afflicted dog’s uterus and out through her vagina, as the infection progresses.
There are alternatives to total reproductive sterilization, including partial spay, or simple hysterectomy. This procedure all but eliminates the risk of canine pyometra, but it leaves the ovaries to produce sex hormones, which are the very ones that encourage mammary tumor growth. For the vast majority of normal, healthy puppies, it is perfectly safe to subject them to a standard ovariohysterectomy as early as eight weeks after birth. “Early” can mean different things, depending on the size and breed of dog.
Size and breed factors mean that a dog can have her first estrous cycle as early as 6 months of age and as late as 24 months. There’s no rule that says that spaying must be done at 8 weeks. The health benefits are greatest if she is spayed prior to her first heat. Regardless of where you stand on the issue of early spaying, you should at least consult with your dog’s veterinarian about having the procedure done by the time your female dog is 2.5 years old. That is the point at which studies show that ovariohysterectomy no longer has an impact on preventing mammary tumors.
About the author: Melvin Peña trained as a scholar and teacher of 18th-century British literature before turning his research and writing skills to puppies and kittens. He enjoys making art, hiking, and concert-going, as well as dazzling crowds with operatic karaoke performances. He has a two-year-old female Bluetick Coonhound mix named Baby, and his online life is conveniently encapsulated here.