Ringworm in Cats

Ringworm, while not a disease, is a very difficult condition to work with, and is extremely hard to get rid of. It's also difficult to "contain" because it is so contagious. This explains why facilities that house animals take such drastic measures if they see any evidence of ringworm on any animal, or on any person who could have contact with others.

Ringworm is not fatal, yet it causes skin problems and is hard to eradicate. It is easily spread between all species, meaning that all the animals in one's care, as well as any humans who might touch them, can get it.

Technically known as dermatophytosis, ringworm is caused by a fungus, called a dermatophyte. There are more than 40 kinds of dermatophytes, which tend to be specific for the animal infected, although the one that usually infects cats is the one found on dogs... Microsporum Canis.

Besides acquiring it from an infected victim, ringworm also can be spread by contact with the fungus in soil, particularly if an area has been contaminated by other animals that have rolled in the dirt. Cats also may pick it up from infected rodents, or from each other. Humans most often become infected through contact with a pet that has it.

The spores (the infectious stage of the dermatophyte) are very robust and can live in an environment for about 2 years.

As with many conditions and diseases, the healthier the animal, the less susceptible they are to infection. Ringworm infestation is much more common and more easily contracted if the animal has a weakness, such as being very young (immune systems may not be fully developed yet), previous or existing problems with fleas or mites (which bite and cause breaks in the skin), cats with long hair (protects the spores from sunlight, which may repel them from attaching), and decreased grooming (such as older cats, obese cats that can't reach some spots), or contact with infected grooming tools used on other animals.

How can ringworm be diagnosed? There are 3 main methods in use today:

  • Wood's Lamp. This is an ultraviolet light that can cause the spores to fluoresce in a darkened room, giving off a characteristic apple-green color.
  • Microscopic examination. Simply, this means looking at some hairs plucked from the affected area to see if they are fungal spores.
  • Fungal Culture. This is the only reliable method, as the first two are subjective and inconsistent. Not all spores will light up under the Wood's lamp, and not every sample is conclusive under the microscope. A culture, however, will be sent to a laboratory that has reliable methods and results.

Now, the most important aspect... how is this treated? Ringworm is not fatal and usually not even debilitating. However, it is very uncomfortable due to itching, which causes a lot of scratching activity, which can injure the skin. That alone makes it difficult to eliminate the spores, as that just gives them a warmer and more hospitable spot to renew themselves.

Left alone, ringworm will clear itself, but it takes many weeks. Due to the discomfort, the clearing time takes longer because of self-reinfection. Because of the risk of spreading it during this time, it's extremely important to treat it, then.

Treatment involves several levels of care:

  • Previous or existing skin problems. If lice, ticks, fleas or mites are or have been present, that needs to be handled immediately, as that leaves the skin vulnerable to further infection.
  • Medication specific to the fungal infection. The standard for use in cats for years has been Griseofulvin, though other drugs are available now. They can be obtained from a veterinarian for use in pets, but human infection must be treated by a physician. Griseofulvin must be used with caution, as some cats can have side effects. Pregnant cats probably should not be on it, as it can cause deformities in the young. Cats with other diseases are more susceptible to side effects as well, especially if they have FIV (Feline Immunodeficiency Virus). If the cat is not tolerant to Griseofulvin or is not responding, ask your vet to consider itraconazole or terbinafine.
  • Topical treatment. Avoid using human ointments. These are just not adequate to treat the areas affected. The best approach is to clip the hair away from all lesions, at least 2-3 inches around the area. If there are several, it may be best to shave the cat, being very careful not to injure the skin or the lesion, or you could promote further infection. If necessary, the cat may need to be sedated to do this safely.

    Use a shampoo or a dip to treat the entire cat. Such preparations should be left on for 10 minutes before rinsing. This must be done twice a week. Be careful around the eyes, and use an Elizabethan collar until dry, to prevent the cat from licking. Ask your vet to recommend the correct product. Be aware that most preparations available today are for dogs and cattle and can kill a cat.

  • Treat the environment. Any hairs shaved or clipped off the cat should be burned, not just discarded. Keep the cat in one room or area to avoid continued contamination of the whole environment. Dispose of all bedding used by the cat, preferably by burning also. You can use cardboard boxes for temporary bedding until the problem is gone. Replace them once a week. Frequent vacuuming helps, but does not kill anything. Chemicals that work may not be desirable for use in your home, such as bleach on the carpet. Use it on hard surfaces, however, for effective decontamination.

    Use of any treatments on youngsters should be monitored and carefully dispensed. This includes human children, as well as any kittens that may be affected. As mentioned, youngsters are the most at risk for infection.

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    Copyright 2007 - Dr. RJ Peters 
    The Problem Cat