Persistent Uterine Infections

T he question that begs an answer concerning uterine infections, in the mind of Jim Briddle, DVM, Riverton, Wyo., isn't so much why they occur, but, rather, why they don't occur more frequently.

"It has always been amazing to me," says the Kansas State University graduate and operator of Fremont County Veterinary Hospital, "that we don't get more uterine infections post coitus. After all, the mare's cervix relaxes completely, and when the stallion breeds her, his penis goes through the cervix and all the way into the uterus. Thus, there is great potential for bacteria to be deposited in the uterus."

When uterine infection, or endometritis, does occur, it can spell reproductive problems that range from those that are relatively easily controlled to stubborn bacterial attacks that can prevent pregnancy and even after pregnancy occurs, can bring about embryonic death. (Endometritis refers to inflammation of the tissue lining the lumen of the uterus and is often secondary to a bacterial infection.)

Clinical signs of a mare with endometritis include vaginal and/or cervix discharge, short cycling, and failure to become pregnant.

Treating both short-term and recurring infections includes the use of antibiotics and flushing unwanted debris from the uterus via lavage, along with surgical procedures, such as Caslicks operation. Prevention of the problem in the first place includes improved hygiene at breeding time, making certain the mare's entire system has all of the support it needs in the way of vitamins and proper nutrition, and making use of one of the newer "kids on the block," immunostimulants.

Listed by many veterinarians and researchers as the most common bacteria causing uterine infection is Streptococcus zooepidemicus. Two other prime culprits are Pseudomonas aeruginosa and Klebsiella pneumoniae. Both of these bacterial strains, says Briddle, are tough opponents to conquer.

While a great deal of bacteria can be carried into the uterus during mating, a majority of young mares rapidly eliminate bacterial contamination of the uterus following mating and foaling and are referred to as being resistant to infection, says Patrick McCue, DVM, PhD, Diplomate ACT, of the Department of Clinical Sciences, Colorado State University. (McCue presented a seminar at the Wyoming Veterinary Medical Association Conference in December on this topic.)

There are other mares which might have a failure of the normal uterine defense mechanisms, such as the physical clearance of uterine contents, and are considered to be susceptible to infection.

Once infection or endometritis is diagnosed, the veterinarian must take a course of action aimed at eliminating the source of the infection and wiping out the damaging organisms that are present in the uterus. In order for the practitioner to know what he or she is dealing with specifically, a culture is a necessity, says Briddle. Only when the veterinarian knows exactly what bacterial organism is involved, can the correct decision be made as to which antibiotic is appropriate.

"A practitioner can do a lot with a microscope right there at the clinic," he says. "If there is bacteria present, you are going to be able to see it, and you may be able to determine what general type is involved."

By studying a uterine culture in the clinic, Briddle feels, the practitioner can get a head start on treatment while awaiting official results from a laboratory.

One of the most beneficial services the laboratory provides, he says, is to isolate the bacteria and recommend an antibiotic that sensitivity tests have demonstrated has the capability of destroying it.

One of the procedures the practitioner can perform while awaiting official laboratory results is to cleanse the uterus via uterine lavage. McCue recommends one to two liters of sterile saline, using a balloon-tipped catheter for "mechanical evacuation of uterine contents, repeated until the fluid recovered is relatively clear."

Oxytocin, with 20 IU administered either intravenously or intramuscularly, might promote uterine contractions for evacuation of uterine fluid.

While the practitioner might be able to correctly guess which antibiotic is best suited to combat the infection, the laboratory culture and sensitivity tests can provide a more certain indicator.

"When we treat without a culture or without knowing the complete results of a culture," says Briddle, "we call it shotgun therapy. If we hit with the right antibiotic, we consider ourselves lucky."

Listed by McCue as antibiotics that have been effective in combating uterine infections are Amikacin, Ampicillin, Gentocin, K Penicillin, and Ticarcillin.

Getting the infection completely cleared up is of utmost importance, because if it flares up again during pregnancy, it can cause embryonic death and additional uterine damage.

Pseudomonas is one of the bacterial infections that is chronic in nature, says Briddle. "We can clear it up, but it seems to keep coming back."

The answer to defeating stubborn bacteria?

"Palpate, palpate, palpate, and culture, culture, culture," says Briddle.

Palpation lets the practitioner determine the tone of the uterus and cervix, size and consistency of ovarian follicles, presence of a recent ovulation, or a corpus luteum. Cultures taken at the same time let the veterinarian and owner know whether infectious agents are present in the uterus.

With a mare which is susceptible to uterine infection, one of the important weapons that can help ward off the infection is artificial insemination. By using a pipette that is free of contamination instead of the stallion's penis to deposit sperm, contaminants presented during natural cover are avoided.

However, that is not the answer for Thoroughbreds, for which artificial insemination is not approved by the breed registry.

When natural cover is the only option, says Briddle, one must take every step possible to free the stallion's penis of contamination. A thorough cleansing of the penis with warm water (and sometimes mild soap) can remove most of the normal contaminants. The area around the mare's vagina should also be thoroughly cleansed.

Conformation and Infection

The perineal conformation of the mare--the manner in which the anus and vagina are structured--can be a significant factor in recurring uterine infection.

One of the common problems in older mares results when the supporting structures of the perineal area relax, allowing the vulva to tilt forward. When the mare defecates, the manure rolls across the vulva and bacteria frequently makes its entrance through the vagina, travels to the cervix, passes through it, and sets up shop in the uterus.

Once a mare with this type of problem is cleared of infection and impregnated, the management technique of choice often is episioplasty or Caslicks operation, in which the vulva is sutured, leaving only an opening for urination.

Another condition that is often implicated in uterine infections is pneumovaginal, also known as wind sucking. In these instances, poor perineal conformation and reduced muscular tone to the vulva allow the vulva to open inappropriately, which, in turn, allows airborne bacteria to enter the vagina and make its way into the uterus.

Still another culprit is urine pooling. This happens most often in older mares where the vaginal vault slopes forward and toward the abdomen of the mare. During urination, some of the urine refluxes forward into the vagina instead of being voided outside.

In these cases, urine often covers the cervix and might even enter the uterus when the cervix is in a relaxed state during estrus. Urine, says McCue, causes moderate to severe inflammation of the cervix and endometrium and might consequently be a cause of infertility.

The problem can be solved through surgery that involves a urethral extension.

While the most immediate product of uterine infection includes prevention of pregnancy and embryonic death after pregnancy, there are other, long-lasting effects that remain after the bacterial infection itself is cleared up. One of the most common long-lasting effects is the formation of scar tissue in the uterus. When scar tissue reaches an advanced state, it renders the uterus uninhabitable for a fetus.

Sometimes there is a formation of scar tissue that can partially or completely close the cervix, resulting in an inability of the mare to clear fluid from the uterus or an inability of sperm to gain access to the upper portions of the reproductive tract for fertilization.

Problems also can result from cervical lacerations during either breeding or foaling. This type of injury might result in a cervix that does not seal properly, allowing bacteria to gain entrance into the uterus during diestrus.

Interestingly, though Briddle's practice involves a good deal of work with mares during the breeding season, he has faced few problems with recurring uterine infections.

"I think one of our strong points," he says, "is the fact that our winters are cold enough that the bacterial flora perhaps doesn't have a chance to over-winter or build up a reservoir as it might in a warmer, more moist climate. In addition, we in the inter-mountain states have a lack of humidity. Bacteria loves a warm, moist setting, and we don't have it."


While palpations and frequent cultures are the keys to detecting uterine infections in their early stages, Briddle is of the opinion that the horse owner can be a significant role player in the prevention phase.

"It involves the theory of treating the whole horse instead of simply targeting a specific area, such as the uterus," he says. "I'm not a truly holistic practitioner as some of my colleagues are, but I do believe in supportive medicine. If we have a problem, we should be thinking of all the ways we can to support that animal's system. We are talking about a whole animal here, not just a metritis of the uterus."

Dealing with the whole animal, in his opinion, involves making certain it has access to high levels of Vitamin A, Vitamin E, and Vitamin C.

"I know Vitamin C may be controversial," he says, "but I consider it to be an immune enhancer."

Briddle also is a believer in immunostimulants as part of the protocol in both the prevention and treatment of bacterial infection of the uterus. Immunostimulants, produced from naturally occurring bacteria, are designed to stimulate an animal's immune system so that it is better able to manufacture its own disease-fighting components.

A study by Alex C. Zingher, DVM, of Charleston, Ill., bears out Briddle's assertions concerning the use of immunostimulants.

In his study, Zingher used an immunostimulant made from the naturally occurring bacteria Propionibacterium acnes on 37 barren mares, primarily Standardbreds, diagnosed with active bacterial endometritis. Their average age was 13 years and the average number of foals produced was four. Many of the mares had histories of extensive intrauterine antibiotic therapy.

As the mares were diagnosed with endometritis by using uterine cultures, they were randomly assigned to either a treatment group or a control group.

The treatment group, which ultimately totaled 21 in number, was treated with the immunostimulant by injecting one milliliter per 250 pounds of body weight intravenously on Days 1, 2, and 7 following the diagnosis of endometritis. The control group, which totaled 16 in number, received no treatment.

Following treatment, diestrus was shortened in both groups of mares by prostaglandin injections given seven days after the end of behavioral estrus.

Eleven of the 21 mares in the original treatment group became pregnant to 60 days or more following breeding on the first estrus in the wake of treatment. Of the 10 mares remaining in the treatment group, eight were confirmed as free from inflammation by cytology.

In the control group, 14 of the 16 mares were found to be positive for inflammation on the first estrus subsequent to non-treatment and prostaglandin injection. These mares then were treated with the immuno-
stimulant, and it resulted in six of them becoming pregnant to 60 days.

In summary, Zingher reported: "Nineteen of 21 mares in the treatment group either became pregnant to 60 days or had negative post-treatment endometrial cytology. Fourteen of 16 control mares remained positive for inflammation. Subsequently, six of the positive control mares responded to treatment with the immunostimulant."

The best way to avoid the problems of recurring uterine infections, says Briddle, is to use every possible means to prevent it in the first place. If and when those steps fail, it is time to step in with the correct antibiotic, lavage, and appropriate surgical procedures.

About the Author

Les Sellnow

Les Sellnow is a free-lance writer based near Riverton, Wyo. He specializes in articles on equine research, and operates a ranch where he raises horses and livestock. He has authored several fiction and non-fiction books, including Understanding Equine Lameness and Understanding The Young Horse, published by Eclipse Press and available at or by calling 800/582-5604.

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