Once dermatophytosis is diagnosed the treatment goals will be to eliminate the fungi from the dog’s skin, restore hair and skin to a normal condition and prevent the spread of infection to other family members. Therefore, treatment for dermatophytosis will involve the combination of topical, systemic therapy and sanitizing environmental contamination. Show Topical Treatments Topical treatments are best if applied to the dog’s whole body, in the form of shampoos, rinses or dips. Your veterinarian may suggest clipping or shaving your pet’s hair to help aid with the treatment. Topical treatments usually must be continued for at least 4 to 6 weeks. Some topical solutions that have been found effective against dermatophytosis include sulfur sulfide, enilconazole, chlorhexidine + miconazole and chlorhexidine + ketoconazole. Isolated lesions may be spot treated with a prescribed anti-fungal ointment. After bathing or applying ointment to your pet make sure to wash your hands and sanitize any surfaces the dog had contacted with. Systemic Treatments Oral antifungal drugs that your veterinarian may prescribe include griseofulvin, terbinafine, lufenuron and itraconazole. Each of these medications may have side effects, so must have close direct veterinary supervision. Antifungals never should be given to pregnant pets because they may cause defects in the litter. Oral treatment usually must be continued for at least six weeks. Your veterinarian team will take dermatophytosis cultures one to two weeks after the start of treatment to help determine if your pet is still infected. Commonly, two consecutive negative cultures will indicate that your pet is no longer infected. Environmental Sanitizing Fungal spores can be shed into the environment and infect other animals or humans in the household. Your pet’s living environment must be frequently disinfected, vacuumed and mopped. Your pet’s bed and toys must be washed. A bleach diluted solution is recommended in areas that can be disinfected. Air filters should be changed frequently. Your veterinarian may recommend restricting your pet to an area that is easy to maintain as sanitary. Top
Animals can be treated to shorten the course of the disease and minimize contagion to other susceptible animals or people. Infected small animals should be kept isolated from other pets until there is clear evidence of clinical cure. Young animals should not be overly confined or undersocialized, or lifelong behavioral problems may occur.
Cats can be treated with itraconazole (5 mg/kg, PO, once daily on a week on/week off schedule). Most infections are resolved after 3 or 4 cycles. An evidence-based review found that itraconazole is well tolerated in cats and was not associated with liver toxicity or vasculitis. Compounded itraconazole should not be used however. Poor bioavailability has been documented for such formulations, so a commercial veterinary liquid formulation should be used.
Small dogs can be treated with oral itraconazole (5 mg/kg, once daily); pulse therapy is likely to be effective, but this has not been documented. Other dogs can be treated with ketoconazole (5 mg/kg, once daily) or terbinafine (30–40 mg/kg, once daily).
Other points to keep in mind regarding drug therapy for dermatophytosis include:
In addition to systemic treatment, topical therapy is required because it disinfects the hair coat. This is important because infective spores are the source of contagion and transmission, and disinfection minimizes environmental contamination. A whole body rinse (lime sulfur 1:16 or enilconazole 1:100) should be used twice a week; these products have residual activity. Shampoo containing 2% chlorhexidine and 2% miconazole is effective and may be the only option in countries where lime sulfur or enilconazole is not available; shampoo therapy has no residual activity. Even if systemic therapy is stopped, topical therapy should be continued until a mycologic cure is demonstrated.
Adjunct focal topical therapy can be used for lesions in hard-to-treat locations such as the ears and face. A 1%–2% vaginal miconazole cream can safely be used on the face. For the ears, otic products that contain clotrimazole or miconazole/chlorhexidine or ketoconazole/chlorhexidine combinations are available.
Environmental cleaning removes infective material from the environment. Spores do not multiply in the environment and do not invade the environment like mildew. Spores are a normal dormant life stage of dermatophytes and other microorganisms and are easily removed from the environment. Mechanical removal of organic material and hair followed by washing of the surface with a detergent until visibly clear is the most important step for environmental cleaning/disinfection. After cleaning, a disinfectant should be used. Any bathroom disinfectant labelled as effective against Trichophyton will kill any spores not removed by mechanical cleaning. Disinfectant use alone will not remove environmental contamination. Thorough cleaning once or twice a week is adequate. Between cleanings, remove organic material with wipes or other means. Soft surfaces such as bedding or towels can be disinfected via washing; bleach is not needed. Carpets can be disinfected via carpet shampooing or steam cleaning.
The end point of treatment includes both clinical and mycologic cure. Clinical cure is the resolution of all lesions and the lack of any new lesions. A Wood's lamp examination can be used to look for areas of residually infected hairs in animals with M canis infections. Once lesions have resolved and there is a clear clinical cure, a fungal culture or PCR can test for mycologic cure. One negative PCR test supports a mycologic cure. Unless the animal has systemic illness, one negative fungal culture also supports mycologic cure.
Red, circular skin lesions: this tell-tale sign of ringworm is unmistakable, whether it appears on you or your dog. But despite its name, ringworm in dogs isn't always a round lesion or a worm— it's a common skin infection that's highly contagious. In cases of dog ringworm, these lesions typically appear on the face, ears, tail or feet. While these infected areas are pretty easy to spot, ringworm can also spread to other, more hidden, areas of your pet's body, which can make its transmission all too easy. The good news is that while dog ringworm is pesky, it's also highly preventable and fairly easy to treat. How Is Ringworm in Dogs Spread?Dogs often acquire ringworm — or dermatophytosis, as your veterinarian might refer to it — from digging. It's relatively easy to treat and doesn't cause severe disease. However, ringworm in dogs can be difficult to manage, due to the fact that it's highly contagious and can be transmitted via fomites. A fomite is any object or material that can carry an infection. In short, anything your pet touches can harbor and transmit ringworm to other dogs, cats or people. Any brushes, bedding, food, water bowls or toys — anything your dog comes in contact with — should be disinfected if ringworm enters the picture. Additionally, any infected dog is considered highly contagious to other animals and humans. Wear gloves or wash your hands and clothes after handling your pet, and keep them quarantined until your vet declares that they're free of infection. Does Ringworm in Dogs Affect All Breeds?Not all dogs that come in contact with ringworm will show signs of an infection. Ringworm infections depend on the type of fungus, as well as the dog's age, relative health, nutrition and grooming. Any dog can develop a ringworm infection, however, certain age ranges and breeds are more at risk. In an article for DVM360, veterinary dermatologist Anthea Schick says Boston terriers, Yorkies and Jack Russell terriers are all prone to contracting ringworm. Very old dogs, puppies and dogs who have a suppressed immune system, she continues, are at an increased risk for developing ringworm. Dogs with ringworm are contagious to humans. If your dog has been diagnosed, or if you suspect they may have ringworm, do not handle them and then directly touch your skin. Wash your hands after every touch, and if you notice any red, circular itchy spots on your own skin, call your doctor. How Is Dog Ringworm Diagnosed and Treated?Your vet will usually diagnose ringworm via physical examination and one or more simple lab tests. The Wood's Lamp, fungal culture and direct examination of hairs under a microscope are the most common ways of diagnosing ringworm. Occasionally, ringworm in dogs is diagnosed via skin biopsy or polymerase chain reaction (PCR) from samples sent to a reference lab. Ringworm is treated with antifungal medication, either topical, oral or a combination of both. There are several lotions, creams and shampoos available by prescription from your vet as well. Ringworm can also be treated with prescription-only oral antifungal medication. Dogs are often shaved in the area of infection to help prevent the spread of disease through contaminated hair. In some cases, ringworm infections can return; however, treatment in these dogs can still speed healing and reduce the likelihood of the disease being transmitted to other animals or humans. How to Decontaminate Your Home After a Ringworm DiagnosisRemember, ringworm loves to travel and infect new hosts via fomites, which is why a key part of treating it is to disinfect your home. If your dog has ringworm, vets recommend:
In severe cases in which you have children at home or more than one pup, you may also want to clean your home's air ducts and replace any air filters. Is Ringworm in Dogs Preventable?One way to prevent ringworm is to not let your dog dig in rodent holes, as this is how infection often occurs. The likelihood of a ringworm infection can also be reduced by making sure your dog is in otherwise good health. If you take your dog in once or twice a year for vet wellness visits, follow all their recommendations and practice preventative nutrition by feeding them a complete and balanced diet, you'll be well on your way to keeping ringworm away.
Dr. Sarah Wooten Dr. Sarah Wooten graduated from UC Davis School of Veterinary Medicine in 2002. A member of the American Society of Veterinary Journalists, Dr. Wooten divides her professional time between small animal practice in Greeley, Colorado, public speaking on associate issues, leadership, and client communication, and writing. She enjoys camping with her family, skiing, SCUBA, and participating in triathlons. |
