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Physical and Medical Effects

Intact bitches are susceptible to several diseases of the reproductive tract and mammary glands. Removing the ovaries and uterus greatly decreases or eliminates the risk of a bitch developing the following disorders:

1) Mammary cancer. Mammary gland cancer is the most common tumor of the sexually intact bitch. The beneficial effects of bilateral ovariohysterectomy in preventing the development of mammary cancer have been well documented4.

Sexually intact bitches have three to seven times the risk of developing mammary gland cancer compared to neutered bitches. The timing of neutering is critical if mammary cancer is to be avoided. Bitches spayed prior to their first estrus have been reported to have 0.5 percent risk of developing mammary cancer. If spaying is delayed for one to two heat periods, however, the chance of a female developing a tumor jumps to 8 and 26 percent, respectively. Little sparing effect is seen in bitches neutered later in life.

Regardless of age, ovariohysterectomy is often performed concurrently with mammary tumor removal. The reason for this is that a number of these tumors have the potential to metastasize to other areas of the body. The cells which have metastasized, like the parent mammary cancer cells, are often stimulated by female sex hormones. Ovariohyslereclomy removes the source of female hormones and thereby decreases progression of the disease.

2) Pyometra. Meaning "pus in the uterus," pyometra is a common disease of intact bitches, usually affecting individuals over six years of age. This condition develops as a result of the influence of progesterone on the uterus during diestrus. Progesterone promotes growth of the endometrium (the lining of the uterus), and secretion of uterine glands. These secretions provide a me-dium for bacterial growth. In addition, progesterone inhibits the infection-fighting activities of uterine white blood cells.

Signs of pyometra include varying degrees of illness along with an increase in drinking and urination in an older intact bitch. Blood analysis and abdominal radiographs are used to confirm clinical suspicion. Ovariohysterectomy is the only acceptable treatment for pyometra. Medical treatment using antibiotics, prostaglandins, hormones and supportive therapy is generally unsuccessful. Removal of the uterus and ovaries at any age will prevent development of pyometra.

3) Vaginal prolapse. This condition occurs in response to the effects of estrogen on the lining of the vagina. Estrogen causes this tissue to become edematous (swollen) and protrude from the vulva, becoming subject to trauma or self-mutilation by the bitch. Ovariohysterectomy prevents this condition from developing.

Potential adverse effects of ovariohysterectomy are uncommon and of less significance than the beneficial effects. A condition of estrogen-responsive urinary incontinence develops in a small proportion of spayed bitches (one researcher found a 4 percent incidence10). The incontinence condition generally responds to treatment with oral medication.

Many individuals feel that their bitch should go through one estrous cycle prior to being spayed. There is one situation in which this should be considered—the case of puppy vaginitis. Some puppy bitches develop a vaginitis because the lining of their vagina is thin. This is often alleviated after one estrous cycle. The effect of the estrogen produced during the estrous cycle is to thicken the vaginal lining, making it less susceptible to infection. If a bitch who has been spayed before her first estrous cycle continues to exhibit signs of vaginitis, antibiotic and hormone therapy may be initiated to treat the problem.

The Early Sterilization Program

Dr. Michael Aronsohn, director of the Early Sterilization Program (ESP) at the Massachusetts SPCA's Angell Memorial Animal Hospital, sees .the. ESP as a boon to pure-bred dog breeders.

"The program is useful to breeders because they can get pet quality puppies neutered as early as six weeks of age,.prior to placing them in homes," says Dr. Aronsohn, a Diplomate of the American College of Veterinary Surgeons and head of the Department of Surgery at Angell Memorial's affiliated Boston shelter. "Breeders can bring in litters to be neutered and the puppies will be ready to go to their new homes•a few days after surgery.

Dr. Aronsohn and anesthesiologist Dr. Alicia Faggella have ! neutered several hundred puppies and kittens with no apparent ill effects. At another animal shelter, in Medford, Oregon, a study of 8,000 puppies and kittens neutered at eight to 12 weeks of age also reported no undesirable effects.1

When asked about the safety of early neutering, which has been in existence for nearly 20 years, Dr. Aronsohn replied, "Anesthetic protocols have been worked out, and are as safe in the younger puppies as they are in the ones five to eight months old. We previously thought that, hypoglycemia was going to be a problem, but it has turned out not to be."

The Angell Memorial team has neutered litters of puppies "and kittens as young as six to eight weeks old for several area breeders. Dr. Aronsohn recommends that interested breeders contact their local humane association for information on shelters and hospitals in their area that perform early neutering.—RM

l. Kellington E, Hannawalt EH. Study of the effects of early spaying and neutering. Medford, Oregon SPCA Rep. May 1985.

In the absence of puppy vaginitis, there is no reason that a bitch should not be spayed prior to her first estrus. The sparing effect on mammary cancer development alone is reason enough not to delay ovariohysterectomy.



Beneficial Effects of Castration

Neutered dogs are at less risk of developing some diseases than their sexually intact counterparts. The most important of these are prostatic disease and testicular cancer.

Benign prostatic hypertrophy is an androgen (male sex hormone) related disorder of the prostate gland in which the gland enlarges and becomes more susceptible to infection. Prostatic infection may spread to involve the bloodstream (sepsis) or abdominal cavity, and may result in death. Benign prostatic hypertrophy is both prevented and treated by castration.

Testicular cancer is a potential danger to intact male dogs. Cryptorchid dogs are actually at greater risk of developing testicular cancer than normal intact dogs. In one study of 410

dogs cryptorchids were found to have 13.6 times the risk of normal dogs for developing testicular cancer11. Sertoli cell tumors are a type of cancer more often seen in cryptorchids than in intact males. This condition can cause a life-threatening bone marrow suppression.