“MRSA” Can Affect People and Horses

But don't panic: healthy horse / healthy rider practices can protect you and your animals

Karen Helton Rhodes, DVM & Terri Bonenberger , DVM Board Certified Veterinary Dermatologists


Heading to Florida Soon?

The mass migration of the equine community to warmer climates during the winter season is a timely reason to raise the alarm about MRSA. Warm humid temperatures associated with dense populations of horses (and dogs) that have recently been “stressed” with extended travel and arrival at a new home create the perfect storm.

Horses and those people directly in contact with horses have a higher incidence of being colonized with Staph bacteria than the “non-horse” population. Focus on prevention so that you do not have to worry about treatment!

What is MRSA?

This is the nickname (pronounced “mersa”) given to the multi-drug resistant form of the bacteria Staphylococcus aureus. Staph. aureus commonly lives on human skin and inside people’s noses (called “colonization”). If the bacteria enter the body through a cut or scrape it can lead to skin or soft tissue infection. People staying in a hospital or living in crowded conditions are at particular risk for MRSA infection.

Horses are similar to people in that they also harbor the “aureus” strain of bacteria. Methicillin-resistant Staphylococcus (MRS) bacterial skin infections are an increasing problem in both human and veterinary medicine. Not ALL Staph infections are multi-drug resistant but staph infections are now the leading cause of community-associated infections in both people and horses.


Is my horse exposed to MRSA?

Once considered a “rare” diagnosis, resistant staph infections are now quite common and pose a serious therapeutic challenge. MRSA has now established itself as an endemic pathogen in many horse populations and typically manifests as sporadic skin infections.

This widespread problem is likely due, in part, to antibiotic over-usage. Repeated use of antibiotics, often unwarranted, has selectively allowed for strains of bacteria to emerge that have been able to reproduce in the presence of these antibiotics. These strains are now multi-drug resistant making them difficult to treat.

Buzz words that might indicate you and your horse are dealing with a resistant strain of bacteria include:

    • Scratches
    • Mud fever
    • Dew poisoning
    • Pastern dermatitis
    • Folliculitis
    • Rash
    • “Fungus” (typically misdiagnosed)


What does MRSA look like in a horse?

There can be a number of clinical presentations in the horse; making a visual diagnosis very difficult. The skin is often red, crusted, swollen, and may crack and bleed. Lesions are quite common on the legs and are often termed “pastern dermatitis,” “scratches,” or “mud fever.” There may also be small crusts with tufted hair generalized over the entire body or a more localized pattern concentrated along saddle pad contact regions.

These skin disorders are not uncommon or unusual but are very often persistent and frustrating. How many of you have battled any of the above issues with only partial improvement or recurrent flares?

Severe cases occur when the infection is localized in joints or deep tissue. Surgical sites are especially susceptible. MRSA infections have also been reported to cause sinus infections, pneumonia, mammary and uterine infections. The problem with MRSA in the horse is that it does not respond to traditional treatments.

To diagnose if your horse has MRSA, a skin swab or tissue sample must be cultured (incubated on special media). The resultant bacterial growth is then identified in the laboratory followed by an antibiotic sensitivity panel run on the organism. This diagnostic test (culture & sensitivity) will identify an appropriate antibiotic choice. That antibiotic will likely NOT fall within the routine choices used in equine medicine due to multi-drug resistance.


Why is MRSA difficult to treat?

Most staph infections are easily treated with a class of antibiotics called beta-lactams, but when these bacteria develop resistance to the antibiotic methicillin it means that beta-lactams will not work. In these cases, it may be necessary to prescribe antibiotics that may be less effective, more expensive and/or carry greater side effects. The antibiotic choices for treatment are often VERY limited. Topical therapy is often the best and safest option.

Treatment facts:

    1. Severe cases may require a systemic antibiotic selected by a culture & sensitivity panel (often with limited options).
    2. Topical therapy is vital & may be the only treatment necessary.
    3. Sodium hypochlorite topical products are highly effective since no known bacterial resistance has been documented with this ingredient. This ingredient kills bacteria but is not an antibiotic; because of that it does not contribute to antibiotic resistance.
    4. Treat any active infections until clear.


Can I be exposed to MRSA by my horse?

Yes. In a large pilot study conducted at a national veterinary meeting where participants submitted nasal swabs for culture, it was found that equine veterinarians and those individuals that owned or worked with horses had a higher incidence of colonization with MRSA than small animal veterinarians. A similar study was done among veterinary dermatologists. Once again, horse owners within the group had a higher rate of colonization.


What can I do to prevent my horse from contracting MRSA?

The equine athlete requires a sports hygiene program much like you would expect for the student engaging in community/school sports, i.e. wrestling, shared locker rooms, etc. Community-acquired staph infections for both horses and people are more common than the public is aware.

Prevention is better than treating an active infection of the skin. We must focus on antibiotic alternatives such as topical therapy (shampoos, rinses, sprays, lotions, etc). Topicals can be used as a sole treatment of milder infections and thus help decrease the frequency of antibiotic use. Repeated antibiotic usage is one of the major risk factors for resistant infections.

Prevention Tips:

Horse owners should take this information and implement preventative measures:

    1. Hand hygiene - routine hand washing is the single most important infection control practice for personnel in stables!
    2. Minimize grooming contact with new or transient horses.
    3. Minimize horse-to-horse contact with new or transient horses.
    4. Use individual brushes and grooming equipment for horses (especially for those with active skin disease!)
    5. Use individual equipment for horses (saddle pads, boots, blankets, etc.)
    6. Sodium hypochlorite topical products can prevent infection when used on a routine basis. Start using these products prior to shipping south this winter and continue upon arrival.
Since we suspect that it will be difficult or even impossible to follow all six prevention steps, focus on routine bathing with a medically active shampoo (i.e., sodium hypochlorite) to protect the skin.



Bottom Line: Be PROACTIVE in your treatment of equine skin infections.

Keep in mind the typical “skin rashes” our horses develop as we move to warmer climates for the winter season! The prevention tips outlined above will help create a “healthier horse / healthier rider” environment so that you can focus on enjoying your animals, not treating them–or yourself–for acute or chronic Staph (MRSA or non-MRSA) infections.

About the Authors

Drs. Karen Helton Rhodes and Terri Bonenberger are board certified veterinary dermatologists with over 35 years of combined clinical experience. Through their work and friendship, they realized that horse owners needed greater access to reliable information and effective products to resolve skin problems and promote healthy skin. Their company, Equine Skin Solutions, meets the emergent needs of the equine population with educational materials as well as problem-solving therapeutics to treat and prevent recurrence of equine dermatologic problems. More information and access to effective therapeutics (Equine Skin Solutions Recovery shampoo & spray) can be found on their website HealthySkin4Horses.com.

“The time for evidence- based medicine is here. It is no longer acceptable for equine veterinary dermatology to lapse behind other specialties. Our horses deserve “state of the art” skin care."

Dr. Karen Helton Rhodes, Veterinary Dermatologist