Ten Steps out of Chaos:
What to do When you Suspect an Outbreak of Dermatophytosis (Ringworm)
June 27, 2013 (published)
Karen Moriello, DVM, DACVD; Sandra Newbury, DVM
University of Wisconsin-Madison
Madison, WI
University of California, Davis
Davis, CA

***Acknowledgements: The author would like to acknowledge the “Steps” concept was first described by Dr. Sandra Newbury of the UC Davis Koret Shelter Medicine Program of UC Davis. This discussion is a modification of the program she described. She is also my friend, colleague and research collaborator.

Step 1: Initial Evaluation-Is there Really an Outbreak?

The first and most important step when an outbreak is suspected is to collect information and document that this is truly the problem. Although it has been said that “it is ringworm until proven otherwise” we now know so much more about feline skin diseases this sweeping statement is not accurate. If skin lesions are found on a cat or cats in a multiple cat facility, the situation is no different than investigating any other disease. A complete history and review of all of the facts are needed.

  • Action item #1: Get the facts. Prior to having a veterinarian visit the cattery, take the cats to a clinic or have shelter site visit done get information that answers the following questions. Often this can be collected in a telephone call. Key questions to ask include, but are not limited to: What has occurred that raises suspicion that there is an outbreak? What do the skin lesions look like? Where are they located? What population s affected? How many cats are known to have skin lesions? How many are suspected of being exposed? What evaluations have been done-did a veterinarian examine the cats, direct examinations…Wood’s examinations.
  • Action item #2: Pending confirmation that there is an outbreak, keep the cats confined where they are and start “ringworm cleaning”. This is the Triple Cleaning Technique. This is VERY important because no matter what disease is present, cleaning is always beneficial. Isolate suspect cats.

Step 2: Assuming an Outbreak is Confirmed or There is Strong Evidence to Assume the Population is at Risk, the Next Step is to Create a Specific “PLAN” for the Family, Cattery or Shelter.

  • What is important to determine is what can be done? What is the capacity of the organization/family and what impact will it have. It is not helpful to outline a treatment plan that is not affordable or do-able.

Step 3: Establish a “Clean Break Area”

During this step, aggressive cleaning is continues be it in a home, cattery, or shelter. A “clean break” is a way for existing animals (pets) or new unexposed animals to enter the home or facility and not be exposed to the cats with disease. Regardless of the size of the problem, this requires identification of an area that is easy to empty of clutter, clean, and sanitize. It is the area where the cat/cats will be treated until cured. In addition, it involves the identification of a path into the home, cattery, or shelter where new unexposed animals can enter without being exposed to the infected cats.

Step 4: Screening Cats and Exposed Animals

Screening the cats and exposed pets involves: an examination in room light/white light, a Wood’s lamp examination, direct examination of fluorescing hairs, and a fungal culture. During Step 4 of the outbreak response, the exposed population of cats is screened for dermatophytosis. Until the screening process is complete, cats should remain in their current location. Many dermatology texts and this author has previously commented on the lack of value of Wood’s lamp examinations. During outbreak investigations, Wood’s lamp examinations are invaluable often identifying cats with very early limited lesions that could easily be overlooked under a white light examination. If possible, examine cats from least to most likely infected, however depending upon how the facility is organized this may not be possible. What is most important is to be aware of fomite transfer of spores from gloves, towels, and clothing and adhere to appropriate isolation rules to minimize cross contamination.

Step 5 Initial Risk Assessment

Although culture results will not be available for 7 to 14 days, a great deal of information available with which to make treatment decisions. The key here is to determine high versus low risk based upon the initial results from Step 4.

Based upon this information, three groups of cats are identified

  • Lesional, Wood’s lamp positive, direct examination positive (Truly infected cat)
  • Lesional, Wood’s lamp negative. (If the Wood’s lamp examination is negative and the cat has lesions, wait for the culture results)
  • Non-lesional and Wood’s lamp negative

Step Six: Initial Cat Shuffle

This is the first of two “cat shuffles”. It is necessary to perform an initial shuffle to contain the outbreak.

  • Remove known infected cats from the general population and house them in the designated treatment area.
  • Isolate and separate suspect cats pending fungal culture. These would include lesional cats or any non-lesional cat co-mingled with a known infected cat.
  • Treat non-lesional Wood’s lamp negative cats with a topical antifungal rinse (lime sulfur or enilconazole) and follow up based upon culture results.

Using this system, four separate housing areas are needed: the three above and the “clean break”.

Step Seven: Assessing Efficacy of Environmental Cleaning

In Step 1, the first action plan was to institute a “Ringworm Cleaning Protocol”. After the first week of an outbreak response, assess the efficacy of environmental cleaning. It is more important to know that an area is culture negative after cleaning than to have documented contamination at Day 1, particularly when working with limited financial resources. In addition, aggressive cleaning on Day 1 will decrease problems with fomite contamination when cats are screened on Day 2-4. Contaminated environments result in with false positive culture results due to fomite contamination of the hair coat and confound monitoring of treatment.

Step Eight Working with Culture Results

In house fungal culture results should be available between day 7 and day 14. Important reasons for performing in house cultures include the ability to observe the cultures daily, more rapid availability of culture results and the ability to count colony forming units (CFU). Use the number of CFU/plate combined with the presence or absence of lesions is for the final determination of risk assessment and treatment decisions .

Step Nine/Somewhere between Days 7 and 14 after Culture: Shuffle #2

Using fungal culture results, again shuffle cats. Cats that need to be treated are lesional fungal culture positive cats and cats with >10 cfu/plate. Cats that are non-lesional and again Wood’s lamp negative, but have less than 10 cfu/plate present are treated as fomite carriers.

Step Ten: Long Term Response Plan

Without a plan, this is going to happen again!

Notes: Depending upon the number of cat involved many steps can be condensed into one or two days or if the outbreak involves a large number of cats it can take several weeks. What is most important to remember is that this is a curable and treatable disease and the most effective way to prevent spread is through limiting cat movement and good hygiene.