Dermatophytosis is a skin infection with any one or more of a number of fungi, including Microsporum canis, M. gypseum, and Trichophyton mentagrophytes. The common name for this problem is ringworm.
TRANSMISSION is by direct contact with the fungus or with infected skin scale or hair in the enviroment. Infected hairs in the environment can remain contagious for months to years. Zoonosis (contagion to people) is frequent and very often associated with Persian and other long-haired cats. Some pets are asymptomatic carriers; that is, the carry and shed the fungus into the environment but have no signs themselves.
DIAGNOSIS requires fungal culture, a simple test that we run in our hospital. We may be very suspicious of a ringworm infection based on the pet's signs, but culture is necessary.
TREATMENT Both the affected pet(s) and the enviroment should be treated.
TREATMENT: THE PET It is ideal to separate affected pets from other pets in the household until their treatment is completed.Total body clipping can help by decreasing shedding of infected hairs into the environment and allowing easier application of topical treatments. Topical treatment with baths and rinses are effective at removing loose hair and scale from the skin; baths, rinses and lotions have varying effectiveness, but we use them as part of the treatment for most of our patients. Oral medication is the only way to potentially speed up recovery. Fungal vaccines are available, but have shown little effectiveness.
TREATMENT: THE ENVIRONMENT This is the massive, very difficult but very important part. Re-exposure and re-contamination are constant problems. All contaminated pet supplies, including food bowls, toys, bedding, carriers, scratching posts, grooming supplies, etc must be removed from the environment. Any of these items that cannot be washed in a tub or washing machine should be destroyed. Items to be washed should be washed in hot water using an antifungal soap (chlorhexidine), rinsed, and then soaked in a 1:30 dilution of 0.5% bleach for 10 minutes. This should be repeated a minimum of 3 times. All surfaces in the pet's enviroment should be vacuumed, scrubbed, rinsed and wiped down with a 1:30 dilution of bleach. Vacuum bags should be burned or saturated with bleach. Furnace and air conditioner filters need to be changed and discarded once a week. Daily spraying of these filters with a 1:4 chlorhexidine solution will decrease recirculation of fungal spores. Furniture, bed linens, books, lamps, and other surfaces should should be vacuumed and wiped once weekly with the bleach or chlorhexidine solution. Rugs that cannot be destroyed need to be washed with a chlorhexidine solution. (Steam cleaning is not a reliable method of killing fungal spores unless an antifungal disinfectant is added to the cleaning solution.
TREATMENT: DURATION Many pets will appear to heal, but will still culture positive. If they culture positive, then they are continuing to shed the fungus into their environment. The only way to avoid this scenario is to re-culture the patient until one or more cultures is negative.
The shortest possible course of medication is 4 weeks, and the shortest possible culture is two weeks, so the minimum treatment time is 6 weeks. Often, perhaps usually, it is longer.
'I CAN'T BELIEVE ALL THIS IS NECESSARY! WHAT IF I DON'T DO EVERYTHING? WHAT IF I DO NOTHING?" We recommend the treatment outlined above for all affected pets. That said, many of our clients have had success with lesser treatment strategies. Some pets, especially short-haired pets and one-pet-in-the-household pets will respond to minimal medication, and some undergo remission with no treatment at all.