Ringworm or Dermatophytosis

Ringworm…………now there’s a word that can strike fear and trepidation into the hearts of dedicated cat owners everywhere. Ever wonder why?? Well, let’s take a look at this pesky skin infection.

To start with, despite the common name, ringworm is not a worm or wormlike parasite. That common name refers to the "bullseye" raised lesions often seen on the affected animal’s skin. The microscopic organisms responsible for this infection are scientifically known as dermatophytes (fungi) and the infection itself is known as dermatophytosis. The two most common fungi belong to the genus Microsporum and the genus Trichophyton. So, ringworm is a fungal infection of the skin, hair and nails of mammals, including humans (yikes!).

How does my cat get infected?

Ringworm is very contagious and is able to spread from pet to pet, pet to human or human to pet. So how does it do this? Dermatophytes, during their infectious stage, produce spores and these spores are dispersed into the environment. The spores can be anywhere—the soil, pet bedding, tools, your pet’s comb or brush, or in carpets and in your air ducts. These spores can exist in the environment for very long periods of time. The spores attach to the pet’s skin or haircoat and germinate. This produces hyphae, small strands which invade the skin and hair. Skin that is broken or damaged is much more susceptible to infection by the organism. Ringworm seems to be more common in kittens or young cats, and cats that are immunosuppressed. An immature or weakened immune system is less effective at resisting infection.

What are the clinical symptoms of a cat with ringworm?

In the cat the clinical appearance of ringworm is variable. Typical lesions are circular hair loss and scaling or crusting. But not all appear in this form. There can be dry, flaky, reddened skin, broken hairs or hair that comes out easily as well. Pruritis (or itching) may be present. The most common areas of hair loss are on the edges of the ears, around the eyes and on the legs. Some lesions are limited to only the feet causing inflammation of the nail beds and toes.

Lastly, some cats do not exhibit clinical symptoms but can be normal appearing carriers of the fungal organism.

How is my cat diagnosed?

If you suspect your cat may have ringworm it is best to see your family veterinarian. There are many tests which can be performed to help confirm a diagnosis. The Wood’s lamp exam is a start. In a dark room, your veterinarian will shine a Wood’s lamp over your cat’s haircoat. Typically infected hair and skin will be fluorescent yellow green in the dark. However, a negative Wood’s lamp test does not rule out ringworm because not all dermatophytes will fluoresce. Therefore, other testing is warranted for a diagnosis. Suspect hairs can be examined under the microscope to look for spores or hyphae. A far more reliable diagnostic tool is the fungal culture test. Suspect hairs from the cat are placed in a special culture medium tube and incubated for a time period. If the medium changes color this is a positive result. This means that the cat in question is indeed infected with ringworm. Your veterinarian may also want to perform additional diagnostic tests such as a CBC (complete blood count), blood chemistry profile, viral screen, and urinalysis .

How will my cat be treated?

The veterinarian will most likely recommend oral antifungal medication along with an antifungal shampoo. The oral antifungal medication will probably need to be given with food or after a meal. This helps the drug to be absorbed better by the cat’s body. Usually these medications are given once daily for 3 to 6 weeks. This may seem like a long time but it is necessary to completely eliminate the infection. Your veterinarian may wish to perform periodic blood work during treatment to ensure that your pet is not having any problems with the medication.

Some veterinarians may also use a commercially available ringworm vaccine to aid in treatment of your cat. This vaccine does not prevent ringworm but does appear to cause a decrease in clinical symptoms.

Shampooing is necessary to help control environmental contamination. Longhaired cats may be clipped so that shampooing is more effective. Clipped hair should be disposed of in sealed bags. Generally your pet will need to be shampooed once or twice weekly for 3 to 6 weeks with an antifungal and antibacterial shampoo recommended by your veterinarian. This product should be placed on the animal’s dampened coat, lathered and massaged into the skin and allowed to sit for several minutes to be effective. It is then rinsed off completely. If a caregiver is bathing the cat they should take proper precautions to protect themselves from getting infected. This would involve wearing rubber gloves, a face mask, and eye cover while bathing the cat and making sure to disinfect clippers or scissors if they are used. Other considerations for the owner include quarantining infected animals especially if there are other pets in the household, disinfecting contaminated pet bedding by washing with dilute bleach, and destroying toys and other contaminated items that cannot be easily disinfected. Follow-up visits with your veterinarian are also carried out to make sure the infection is eliminated.

Tell me more about the risks to people…..

As previously stated, ringworm is highly contagious between pets and people. Children and people who have a weakened immune system are especially vulnerable so it is important to minimize their exposure to infected animals. Whenever you handle the infected cat, either wear gloves or make sure you wash your exposed skin with warm water and soap. Do not break the skin. Keeping the infected cat isolated will help prevent unnecessary exposure of other pets and family members to the fungus. If any skin lesions and itching are noted on you or your children consult your physician immediately. Make sure you tell the human health care professional that there has been exposure to ringworm.