Dermatophytosis is a superficial fungal infection of the keratinized tissues, caused mainly by Microsporum canis that occurs more commonly in young cats, less than 1 year old.¹

This dermatological disease is an important zoonosis.

Persian cats are predisposed to developing dermatophytosis and the elimination of the infection in this breed seems to be more difficult, requiring longer treatment courses of systemic therapy. Recurrence of the infection (chronic dermatophytosis) is a very common problem in catteries. Currently, topical treatments are always recommended as adjuvant to systemic therapy and environmental decontamination.¹

There are several treatments and protocols to treat dermatophytosis. In case of great number of animals, as in catteries or in the presence of generalized infection we always indicate systemic therapy, but sometimes there are problems with collateral effects or cost.

Antifungal therapies using griseofulvin, itraconazol, terbinafine are effective and safe. There are also ketoconazole and lufenuron, but the first one can cause collateral effects and the second is not as effective as other treatments.

Pulse therapy consists in administration of an antifungal drug that have the property of accumulation in keratinized tissues, in periods of one week, followed by a period of suspension of the drug for three weeks. These periods of administration are called pulses and we can use cycles of two or three and sometimes more cycles.²

The numbers of cycles needed are based on the negative fungal culture. The endpoints of treatment, independent of the drug choice for therapy, are two or three negative consecutive fungal cultures obtained at bi-weekly intervals.²

Comparing pulse and continuous therapy with terbinafine in a Group of Persian cats with naturally occurring dermatophytosis and asymptomatic carriers we concluded measuring cats´ hair concentrations of terbinafine by high performance liquid chromatography (HPLC) that the therapeutic concentrations were maintained above in pulse therapy in both doses daily oral administration, but there was a higher accumulation of the drug when it was used in the higher dosis and continuous therapy. However emesis was observed in the first week of therapy, and also higher hepatic enzymes serum activities. There were no alterations in the values of ALT and FA in the pulse therapy group. Terbinafine had good efficacy and was safe for the treatment of healthy carriers of M. canis and also for animals with dermatophytosis. So, in our experience, terbinafine in the dose of 20 mg/kg/day is the best choice when using pulse therapy.²

A study in ten healthy cats clinically normal that were administered terbinafine orally at a daily dose of 34-45.7 mg/kg for a total of 14 days and after that was done a determination of the concentrations of terbinafine in cats' hair also by HPLC concluded that terbinafine persists in hair at concentrations above the therapeutic concentrations for several weeks after stopping medication. Even after short-term therapy (14 days). These results suggest that pulse therapy may be very effective for feline dermatophytosis.³

Another option is itraconazole, which was used in nine cats at 10 mg/kg/day orally for 28 days and then alternate week regimen (one week off, one week on) at the same dose. Negative fungal cultures were obtained between 42 and 56 days.⁴

There is also a recent study showing one case of dermatophyte mycetoma in which recurrent generalized dermatophytosis in the Persian cat, after surgically excision, has been managed with pulse therapy using 26 mg/ kg/day terbinafine orally for 1 week in every month.⁵

The owner must observe signs like vomiting, anorexia or jaundice that could indicate liver toxicity and ideally, laboratory monitoring during the antifungal therapy should include at least every month, ALT and FA, mainly in cats that receive prolonged therapies.

Clipping of the hair coat is recommended, but sometimes the owners do not agree with this measure

Chlorhexidine 2%, miconazole 2%, association of these two principals and also ketoconazole 2% shampoos are effective as topical antifungal therapy.⁶

Environmental decontamination has an important role in eradication of dermatophytosis in catteries so it is recommended to use sodium hypochlorite 0.5%, steam cleaning of carpets (at least twice a week) and the cattery should be vacuumed daily.

It is very important that fungal cultures are made before the introduction of new animals in the cattery.

If the topical and systemic therapy (including asymptomatic carriers cats) is correct done and also the environmental decontamination, we should look for the existence of underlying diseases, mainly feline leukemia or immunodeficiency virus (FeLV and FIV).

The vaccination is not recommended for prophylaxis because the humoral immunity is not important in dermatophytic infections, but it can be considered as an adjuvant to conventional therapy.⁶

References

1.  Balda AC, Larsson CE, Otsuka M, et al. Estudo retrospectivo de casuistica das dermatofitoses em caes e gatos atendidos no Serviço de Dermatologia da Faculdade de Medicina Veterinaria e Zootecnia da Universidade de Sao Paulo. Acta Scientiae. 2004; 32(2):133-140.

2.  Balda AC Avaliação das concentrações de terbinafine no pelame de gatos da raça Persa com dermatofitose e daqueles portadores de Microsporum canis tratados em esquema de pulsoterapia ou terapia contínua. 2008. 72 f. Tese (Doutorado em Medicina Veterinária)--Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo.

3.  Colombo S, Cornegliani L, Vercelli A. Efficacy of itraconazole as a combined continuous/pulse therapy in feline dermatophytosis: preliminary results in nine cases. Vet Dermatol. 2001; 12(6):347-50.

4.  Foust AL, Marsella R, Akucewich LH, Kunkle G, et al. Evaluation of persistence of terbinafine in the hair of normal cats after 14 days of daily therapy. Vet Dermatol. 2007;18(4):246-51.

5.  Nuttall TJ, German AJ, Holden SL, et al. Successful resolution of dermatophyte mycetoma following terbinafine treatment in two cats. Vet Dermatol. 2008;19(6):405-10.

6.  Moriello KA. Treatment of dermatophytosis in dogs and cats: review of published studies. Vet Dermatol. 2004; 15(2):99-107.