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Horse Owners Can Help Rein in Antibiotic Resistance

Pet Column for the week of February 19, 2001

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
By Carrie Gustavson
Information Specialist

Although the thought of supergerms floating around your barn or home may seem like something from a science-fiction movie, it's not. Bacteria multiply exponentially in practically no time. That and their ability to adapt to a changing environment make battling an infection more complex than just popping a few pills.

"Because of the risk of antibiotic-associated problems, antibiotics should be used only under the direction of a veterinarian fully familiar with the horse and its problem," says Dr. David Freeman, equine surgeon at the University of Illinois Veterinary Teaching Hospital in Urbana. "To treat an infection with antibiotics, you really have to base your choice on the organism involved, which is identified by culturing an aspirate from the infected tissue."

Overuse and misuse of antibiotics have led to the spread of resistant bacteria. Antibiotic-resistant bacteria may arise from many sources; agricultural use of antibiotics, medical misuse, and antibacterial cleaners are suspected sources. But any time antibiotics are used when they are not truly necessary makes the problem worse.

Horse owners can play a role to help curb antibiotic resistance. "People have to be responsible about how they use antibiotics," says Dr. Freeman. "Frivolous use leads to the development of more and more strains of resistant bacteria."

When bacteria develop ways to outfox a certain antibiotic, they are said to be resistant. Resistant bacteria have "learned" how to alter their structure or change their metabolism so that an antibiotic can't do its job -- kill or weaken the bacteria so that the immune system can take over and destroy them. A resistant strain of bacteria can spread the ability to outsmart a certain antibiotic to other types of bacteria that infect animals or people. Resistant bacteria are hard to treat and can cause serious problems and even death.

So the bottom line is, treating your horse -- or any animal -- with antibiotics unnecessarily or in the wrong dose can cause real antibiotic resistance problems for other animals -- and for people. One of the deadliest and most resistant bacteria of all has been established in human and equine infections. That's why horse owners who try to medicate their animals are many times doing more harm than good. "Always consult a veterinarian before you give your horse any medication," says Dr. Freeman.

Dr. Freeman thinks that antibiotic misuse may have already produced so many resistant strains of bacteria that the antibiotics available to veterinarians are not working as well as they once did. Now, both human physicians and veterinarians have just a few antibiotics to rely on when nothing else works.

All horse owners want the best possible treatment for their animal. But, sometimes the best treatment does not include use of antibiotics. Some instances where owners may incorrectly perceive the need for antibiotics are:

  • When the horse has a viral infection. Though it's hard to see your animal feeling down and out, antibiotics will not cure viral infections like equine influenza. Only rest will do the trick.

  • To prevent infection after an operation. "With proper aseptic surgical technique, the risk of infection is extremely low," says Dr. Freeman. Certain surgeries, such as arthroscopy, removal of retained testicles (cryptorchidectomy), and removal of ovaries (ovarioectomy), have been proven to have almost no risk of infection. Even after colic surgery the risk of life-threatening infection is very low. In procedures where a steel plate is inserted to repair a limb fracture, or when an implant is inserted, the risk of infection increases. In those cases, antibiotics may be indicated.

Of course, if a horse is not recovering well from a viral infection or after surgery, a veterinarian can determine if there is a secondary infection, and treat it accordingly.

In addition to promoting resistant strains of bacteria, antibiotic use has several other more immediate disadvantages. One is to your pocketbook -- antibiotics are expensive, especially when you consider treating a 1,000-pound horse.

"If antibiotics do not offer a real advantage in the prevention of infection, the disadvantages are very real," says Dr. Freeman. "Besides the expense, antibiotics can cause swelling, pain, and even an abscess at the injection site. Some horses may have allergic reactions to the antibiotics with widespread effects."

Most importantly, antibiotics can cause colitis and diarrhea, especially in young horses and in horses undergoing the stress of hospitalization, anesthesia, and surgery. "The risk of diarrhea caused by Salmonella species is about six times greater in horses given almost any antibiotic than in horses given no antibiotic. If a horse develops antibiotic-associated diarrhea, its risk of dying is about four times greater than that of a horse that did not receive antibiotics," says Dr. Freeman.

So think of antibiotics as a tool that, when used properly, can be essential to the successful treatment of many bacterial infections. However, it is important to understand the potential side effects, and that misuse can create supergerms able to withstand even the toughest antibiotics. To prevent that from happening, use antibiotics wisely -- and only when a veterinarian has determined that the benefit will far outweigh the risk.