Topical treatment of the hair coat is not considered an optional part of therapy. Topical therapy decreases shedding of infective material, kills ectothrix spores (not affected by systemic therapy1) on the hair coat, helps prevent development of new lesions, and decreases contagion and environmental contamination. Clipping of the hair coat is not routinely needed, but infected hair may be clipped with metal blunt-tip scissors (ie, to avoid microtrauma to skin from electric clippers). The coat should be combed before application to remove loose hairs. Whole-body hair coat disinfection twice weekly is recommended. Patients should be kept warm (eg, with warm blankets) following whole-body treatment to prevent hypothermia.
In vitro and in vivo studies have shown lime sulfur, miconazole/chlorhexidine gluconate, and enilconazole to be consistently effective.1 Leave-on rinses are preferred because of their residual activity and should be applied to the face with a sponge.
Leave-on lime sulfur rinse should be applied twice weekly at a 1:16 dilution. This product, which is not available in all countries, may discolor the hair coat and is somewhat odorous. It will also stain fabric and discolor items in contact with it; owners must wear gloves when applying the product and should not let it come into contact with watches or jewelry. Owners should be educated about proper dilution, as concentrated application can be irritating to the skin. Lime sulfur is efficacious, is immediately sporicidal, and has residual activity. Lime sulfur can be drying to the hair coat or footpads when used for prolonged periods. In the author’s experience in shelters, oral ulcers were never observed as a result of use of lime sulfur; cats with oral ulcers had concurrent respiratory infections.
Miconazole (2%)/chlorhexidine gluconate (2%) shampoo is widely available and is sporicidal but does not have residual activity. Although no in vivo studies have determined the optimal contact time, an in vitro study found that 3 minutes of contact was sporicidal10; therefore, 3 to 10 minutes of contact is recommended. This shampoo can also be used for treatment of exposed but uninfected animals in the home.
Enilconazole leave-on emulsion (1:50 or 1:100) is only labeled for use in cats in France and is not available in all countries. The emulsion is slightly odorous and may be greasy.
Adjuvant focal topical therapy applied once daily is recommended for focal lesions and/or lesions in areas that are difficult to treat (eg, face, ears). This is in contrast to recommendations in most veterinary dermatology textbooks that recommend application twice daily. A recent in vitro study demonstrated good residual activity of clotrimazole (1%), terbinafine (1%), miconazole (0.2%, 1%, or 2%), and 3 leave-on mousse products containing chlorhexidine and climbazole, miconazole, or ketoconazole.10 Mousse products may be suitable for animals that cannot be wetted or are difficult to treat. Care must be taken to use the product as directed by the manufacturer. For periocular lesions, 2% miconazole nitrate vaginal cream is recommended11,12; this product is widely used with proven safety by ophthalmologists to treat fungal keratitis. Lesions on or in the ears are best treated with otic preparations with antifungal efficacy.
Owners should always wear gloves when applying topical therapy.