Is it Ringworm?

By Colleen Mendelsohn, DVM
Diplomate American College of Veterinary Dermatology

Three species of ringworm cause the majority of infections: Microsporum canis, Microsporum gypseum, and Trichophyton mentagrophytes; with Microsporum canis being the most commonly seen and it is more common in cats than dogs. It is often forgotten as a potential problem in adult pets. However, at the same time, lesions of other, more common conditions are frequently mistaken for ringworm, by owners, groomers and animal health care professionals.

Depending on the organism involved, the most common source of infection are other infected pets or contaminated environments (M. canis), rodents (T. mentagrophytes), and occasionally the soil (M. gypseum). In addition to the condition being present in the environment, some animals may act as carriers of the disease with no visible lesions, which then can be passed on to more susceptible animals in the facility. M. canis can survive in the environment for at least 13 months, making reinfection a common problem as well. Therefore, pets that have been treated and resolved could potentially become re–infected and again become a source of the contamination to your facility.

People who come into contact with infected animals are also at risk of developing ringworm. The highest risk are those that have suppressed immune responses including children, the elderly or those with weakened immune responses through disease or medications. As with animals, most individuals who are exposed will not develop an infection.

The symptoms of ringworm are NOT specific. The most common clinical signs of infection are hair loss, broken hairs, and darkening of the skin. The owners will often report that the problem is not itchy. Other signs may include red bumps, itching, crusting, scaling, and occasionally a discharge is noted as well. When the claws are affected, they can become brittle and even break, eventually leading to the claws becoming deformed.

However, a “ring” of scale and hairloss with darkening of the skin is NOT usually a symptom of ringworm, it is more often an indication of a bacterial skin infection (this lesion is referred to as an epidermal collarette), and most often associated with the organism Staphylococcus pseudintermedius. Unlike ringworm, this condition is not contagious and does not pose a risk to the other pets in your care, although, without knowing what is causing the lesion, it is important to properly disinfect any area where a pet with lesions has been.

If any abnormal lesion is noted, let the pet owner know and make sure they seek advice from their veterinarian. When an owner makes an appointment and lets you know in advance that their pet has a skin condition, getting a letter from their veterinarian indicating that it is safe to groom them is also recommended.

Treating ringworm can be a long process. The problem should be treated both topically and systemically (oral medications) in some cases. Even among veterinary dermatologists there is disagreement whether an animal should be shaved for treatment. On the one hand, clipping the coat allows better access for topical medications and shortens the hairs, upon which the organisms thrive. However, shaving a pet that has ringworm contaminates the person doing the shaving, the facility, as well as the grooming equipment. Unless the coat is long and extremely unkempt or an animal is not responding to therapy, shaving the coat is generally avoided.

If your facility is associated with a veterinary hospital and the veterinarian has prescribed topical therapy for a ringworm positive pet, the “dip” or shampoo should be done away from the general grooming area. The bather should wear protective gear and the room should have its own ventilation system. After the bath, the entire area and the vents should be decontaminated. Veterinary dermatologists will recommend that the animal have at least 2 negative cultures about a month apart from each other before they can be declared “disease free”. Additionally, any “in contact” animal should be cultured as well. Ringworm cultures can take up to 3-4 weeks to get a final negative result.

Ringworm is difficult to remove from the environment. Some basic steps include:

• Destroy all fabric bedding, rugs and towels that cannot be washed in a 1:10 bleach solution (0.5%). All surfaces and grooming supplies should be soaked for 5 minutes in a 1:10 bleach solution.

• Clippers, dryers and other items that cannot be soaked should be wiped down as best as possible and “retired” for a few months if possible.

• All heating and cooling ducts and vents should be vacuumed and disinfected.

These procedures should ideally be done before closing to prevent human exposure to the fumes from the concentrated bleach solution.

If a pet has skin lesions, and has been diagnosed with ringworm, then other pets in the house are also sources of infection, as are any articles of clothing, towels or toys that a pet owner might bring with them. Pet owner education is key to making sure that the pets are well taken care of, and that the facility as well as the employees are adequately protected.

Dr. Mendelsohn is a 1997 graduate of UC Davis School of Veterinary Medicine and received Diplomate status with the American College of Veterinary Dermatology in 2004. After graduation from UC Davis, Dr. Mendelsohn completed an internship with the Animal Emergency Clinic and Animal Specialty Group in San Diego. She later practiced general medicine before starting her residency with the Animal Dermatology Clinic in 2000. Her love and appreciation of the human-animal bond is what drew Dr. Mendelsohn to this specialty. Another opportunity that Dr. Mendelsohn enjoys is the training of veterinary students, helping these students appreciate the hidden complexities of dermatologic disease.For more information please visit www.animaldermatology.com.