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4: Dermatophytosis

Ketoconazole is a fungicidal azole drug, used in the treatment of dermatophytosis in the dog. It is not licensed for use in the cat. However, it has been used successfully to treat feline dermatophytosis in many European countries, at a dose of 10 mg/kg SID PO. Its absorption is improved when given in an acid pH, e.g. with food. Side-effects have been reported in the cat: liver problems (e.g. jaundice and elevation of liver enzymes), vomiting, diarrhoea, anorexia and neurological disorders. It may also be teratogenic and should not be given to pregnant females.

Itraconazole is a very useful fungicidal drug. The recommended dose is 10 mg/kg SID PO ^IU2, although a lower dosage (3-5 mg/kg SID PO) also seems effective ¹⁴. Itraconazole appears to be better tolerated by cats than ketoconazole. However, it has been associated with hepatotoxicity in dogs, and liver enzymes should be monitored regularly during therapy. Few side-effects have been seen in the cat, although one report of death due to hepatic necrosis has been reported. Hepatic necrosis appears to be dose-related and can occur in cats receiving morę than 20 mg/kg SID over extended periods of time The use of itraconazole is also contraindicated in pregnant animals.

Vaccination should only be considered an adjuvant therapy or an altemative to topical therapy ". One vaccine is commercially available in the USA for treatment of dermatophytosis in cats and kittens (Fel-0-Vax MC-K, Fort Dodge Laboratories). Used alone, vaccination will not cure dermatophytosis, although experimental data suggest that it might reduce the spread of lesions. To datę, no controlled studies have demonstrated that vaccination will protect against natural or challenge exposure ^l6. Local reactions may occur at the site of vaccination.

Topical therapy is useful because it limits spread to other animals and reduces seeding of the environment with infective materiał. In addition to clipping, it is the most efficient way to loosen and remove infective hairs and crusts from the skin. However, it takes a long time to carry out, especially where large numbers of cats are involved, and some cats will not tolerate topical therapy. Furthermore, clipping combined with topical therapy can actually exacerbate lesions¹⁷. In vitro studies on cat hairs infected with Microsporum canis have shown that the efficacy of many commonly used, topical antifungal preparations is ąuestionable ^l7. The antifungal lotion or shampoo should be applied as gently as possible in order to prevent microtrauma to the skin and iatrogenic rupture of fragile hairs. The coat and skin should be dried as ąuickly as possible as moisture will cause maceration of the epidermis, compromising the natural protective barrier. Care should also be taken to keep young animals warm and prevent them from licking the antifungal solution. Solutions of limę sulphur (1 : 16 dilution) (available in the USA), 0.2% enilconazole and miconazole are very effective^l718. In a smali clinical trial designed to evaluate safety, a group of Persian cats with dermatophytosis were treated twice-weekly with a 0.2% enilconazole solution ^l9. The coat was not clipped. Although there were anecdotal reports of toxicity, all cats tolerated the treatment well. The only side-effects seen were mild reduction in appetite and slight depression. In this study, cats required 8 to 10 weeks of twice-weekly dips before mycological cure was achieved. The manufacturers suggest that 2-3 weeks treatment is enough. Enilconazole is not licensed for use in cats although it is widely used in Europę and Canada.

In rare situations, it may be necessary to treat only the kittens. These kittens should be removed from the queen, as soon as possible, and hand-reared. Altematively, they could be separated from the queen at 4 weeks of age. Fungal cultures can be carried out at this age. If positive, topical therapy alone can be used until the kittens are 8 weeks old. Itraconazole can then be prescribed. Kittens should not be sold until fungal cultures have been negative on at least 2 or 3 successive occasions.

Therapy must be monitored methodically. Dermatophytosis will usually resolve spontaneously within 60 to 100 days in a cat with a competent immune system. Treated cats often show clinical resolution within 4 to 8 weeks, but cats appear clinically normal long before they are cured mycologically. Cats should be treated until fungal culture, carried out weekly, is negative on two or three successive occasions. Fungal cultures should be started after 3 to 4 weeks of therapy. Wood's lamp examination can be used to screen for the presence or absence of infection. However, the limitations of this procedurę should be appreciated. Actively infected hairs tend to glow along the entire shaft or in the proximal region (towards the bulb). Hairs that are no longer infected may still fluoresce along the distal portion or just at the tips of the hairs. These hairs may or may not be positive on culture. False positive cultures can occur in cats that are clinically and mycologically cured, if they are living in a contaminated environment. This is most likely in a breeding colony or cattery. Establishing the true status of these cats, asymptomatically infected or asymptomatic carrier, is difficult. In our experience, these cats frequently have fluctuating culture results, i.e. positive then negative. Additionally, the number of fungal colonies isolated from fomite carrier cats is usually Iow (1 to 5 smali colonies). If there is any doubt, the suspect cat should be isolated in a mycologically sterile cage for 3-5 days before being recultured to determine its true status. In many

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