Environmental detection of Microsporum canis arthrospores in the households of infected cats and dogs

Microsporum canis is the dermatophyte most frequently recovered from canine and feline ringworm cases. The household environment can be contaminated both by symptomatic animals and through asymptomatic M canis carriage, resulting in a potential human health risk. The load of M canis arthrospores was determined in households harbouring infected pets, in order to evaluate the infectivity of the animals versus the environment. The environments inhabited by 30 symptomatic animals (21 cats and 9 dogs) infected by M canis were examined by sampling both surfaces and indoor air. The surfaces were examined by means of contact plates; the air sampling was performed with a Sas super-100 AIR SAMPLER (PBI, Italy). Environmental contamination was detected in all households with cats, while only four out of nine houses harbouring dogs were found positive. The frequence of isolation in each sampling, and the results in terms of colony forming units per plate in the different houses appeared to be quite homogeneous. Heavily infected environments harboured kittens only. Infected owners were observed in eight households, in all of which at least one infected cat was present. No history of human dermatophytosis in households harbouring dogs was found. On the basis of our results, infected cats appear to cause substantial environmental contamination, and provoke a substantial presence of viable airborne fungal elements. Dogs seem to be of lower importance in the spread of M CANIS: they contaminated surfaces, but they never contaminated the air. The results of this study confirm the potential leading role of the feline species in the environmental spread of M canis.     

Terbinafine hydrochloride treatment of Microsporum canis experimentally-induced ringworm in cats

Cats represent the most important source of Microsporum canis infection to people. Terbinafine hydrochloride is commonly used in the treatment of microsporosis. Its fungicidal action permits short period of treatment. It was our objective to evaluate the effectiveness of this drug in treatment of microsporosis in cats. We treated nine experimentally M. canis infected cats with terbinafine at a dose of 10-20mg/kg SID (low-dose group, LDG), nine cats with 30-40mg/kg SID (high-dose group, HDG), and nine cats were left untreated (control group, CG). The drug's levels in cats' plasma and hair were measured by a reversed-phase high performance liquid chromatographic method (RP-HPLC) and the cats' cure was followed by Wood's lamp illumination, microscopic exam and fungal culture. We showed no difference between the clinical course in CG and LDG, but HDG were significantly differentiated from both other groups. Terbinafine levels in plasma at 120 days of treatment were not statistically different among LDG (4.13 microg/l) and HDG (5.48 microg/l), but levels in hair of LDG (1.24 microg/l) and HDG (3.62 microg/l) were significantly different. Terbinafine can be used for the treatment of microsporosis in cats in the dose of 30-40mg/kg SID.     

Efficacy of pre-treatment with lufenuron for the prevention of Microsporum canis infection in a feline direct topical challenge model

Oral lufenuron is reportedly an effective treatment for some cats with dermatophytosis. The purpose of this study was to determine if lufenuron, when used as a pre-treatment prior to challenge exposure, would be protective against the development of infection after the direct topical application of fungal macrocondia (Microsporum canis spores). Three groups (n = 6/group) of juvenile cats were treated with either monthly oral lufenuron (30 or 133 mg/kg) or placebo. After 2 months of treatment, kittens were challenged using 10(5)Microsporum canis spores applied to the skin under occlusion. Cats were examined weekly and the following data collected: Wood's lamp examination; scoring for scale/crust, erythema and induration; lesion size; and the development of satellite lesions. Fungal cultures were performed bi-weekly. All cats became infected; the infections progressed, and then regressed, in a similar fashion in all groups. There were no consistent statistically significant differences in weekly infection scores between treated and untreated cats throughout the study. Treated cats did not recover faster than untreated cats. We conclude that oral lufenuron at the dosing schedule and conditions used in this study did not prevent dermatophytosis or alter the course of infection by direct topical challenge.     

Drug efficacy of terbinafine hydrochloride (Lamisil) during oral treatment of cats,experimentally infected with Microsporum canis

Cats represent a primary source of Microsporum canis infections in humans. Terbinafine hydrochloride (Lamisil) is commonly used in the treatment of microsporosis in humans as its fungicidal action permits short periods of treatment. The aim of the present study was to estimate the efficacy of the drug in cats. Nine cats were experimentally infected with M. canis and treated with terbinafine hydrochloride at a dose of 10-20 mg/kg (once daily, SID; low-dose group, LDG). Another nine cats were similarly infected and treated with 30-40 mg/kg SID (high-dose group, HDG) and a further nine cats were also infected and left untreated (control group, CG). The general condition of the cats was observed daily and their clinical symptoms evaluated weekly. The cats recovery was monitored using the Wood's lamp illumination test and microscopic and fungal culture examinations. The general condition of the cats during the study was good. The cure rates of the LDG were not significantly different from the CG at any period during the treatment. However, the HDG cure rates differed significantly from the other two groups. After 109 days of treatment, when all nine cats of the HDG were healed, seven cats of the LDG and all the cats in the CG were still M. canis-positive. This study shows that dosages of 10-20 mg/kg SID of terbinafine hydrochloride are not sufficient to terminate an experimental M. canis infection in cats within an acceptable period of time. Terbinafine hydrochloride can be used to treat dermatophytosis in cats, but a higher dosage, 30-40 mg/kg SID, should be used to achieve a cure.     

In vitro susceptibility to antimycotics of Microsporum canis isolates from cats.

One hundred thirty-four isolates of Microsporum canis, obtained from cats, were tested for in vitro susceptibility to various antifungal agents. The fungi were classified as susceptible, resistant, and intermediate by measuring the size of the zone of inhibited growth on yeast nitrogen base agar medium. Clotrimazole had the highest activity (99.2%), followed by tioconazole (89.6%), griseofulvin (88.8%), econazole (73.1%), ketoconazole (50.7%), miconazole (15.7%), and isoconazole (12.7%). We found 14.9% of the isolates to be susceptible to all the assayed drugs, whereas the highest resistance frequency (41.8%) was against 2 antimycotics. A simultaneous resistance to all the tested antimycotics was not found. The differences among the antifungal drugs activity were examined, and administration of drugs for which a simultaneous resistance was minimal is suggested.     

Attempted treatment of tigers (Panthera tigris) infected with Microsporum canis.

An outbreak of dermatophytosis caused by Microsporum canis occurred in tigers (Panthera tigris) at an exotic felid sanctuary in 2003. In an attempt to find an effective, practical, safe, and affordable method for controlling this epizootic, a clinical treatment trial was conducted. Nonalopecic tigers were studied to address the inapparent carrier state observed at the facility. The efficacy of three topical and environmental treatment combinations of a 2% lime sulfur solution and a peroxide-based cleaner were evaluated in nonalopecic, culture-positive tigers (n = 18) housed in four separate enclosures. Lime sulfur solution was applied topically to all of these animals. As a control, nonalopecic but culture-positive tigers (n = 6) housed in two other enclosures were not treated. Environmental treatments included lime sulfur solution (n = 1), a peroxide-based cleaner (n = 1), and no treatment (n = 2). All solutions were applied at 2-wk intervals for seven treatments. The 2% lime sulfur solution treatments were unsuccessful in resolving infections in most tigers. Lime sulfur was effective in suppressing environmental fungal growth immediately posttreatment, whereas the peroxide-based cleaner was not effective. A follow-up survey of all study tigers and their enclosures was conducted 2 yr later, at which time 22 of 24 tigers (92%) had attained resolution, defined as two sequential negative hair cultures. Review of the culture results during the clinical trial and follow-up study suggests that nonalopecic dermatophytosis in tigers that are housed outdoors may not warrant aggressive individual or environmental treatment, as the infection may clear with time.     

Microsporum canis: Inapparent carriage by cats and the viability of arthrospores

A total of 181 dermatologically healthy pet cats from 177 different households, attending a veterinary clinic, were sampled for the presence of dermatophytes by a modified MacKenzie hair brush technique. Microsporum canis was the only dermatophyte recovered and was isolated from four cats (2.2 per cent) from four different households. In addition to clinical details, owners were questioned about the environment and management of all the cats sampled. The data regarding the cats from which M canis was recovered showed little variation from that of the culture-negative cats except that all four cats were from multi-cat (more than two cats) households, whereas only 35 per cent of the culture-negative cats were from a similar environment. The viability of M canis in infected feline hairs stored at room temperature was maintained for between 13 and 18 months.     

The prevalence of immediate and delayed type hypersensitivity reactions to Microsporum canis antigens in cats

Spontaneous recovery from Microsporum canis infections in cats is thought to be dependent on the development of a competent immune response. The purpose of this study was to determine the prevalence of positive delayed type hypersensitivity reactions in cats with and without dermatophytosis. Four groups of cats were intradermally skin tested with M canis extract and test sites were evaluated both subjectively and objectively at 0, 24 and 48 h after injection. Delayed intradermal testing (IDT) reactions were absent in cats not exposed to dermatophytosis (n=20); infected-recovered cats (n=38 culture negative lesion negative and n=43 lesion negative but culture positive) had significantly larger IDT reactions than unexposed cats and cats that were still actively infected (n=18). Based on the results of this study, IDT with M canis extract can be used to assess the cellular immune response of cats with dermatophytosis.     

Use of lime sulphur and itraconazole to treat shelter cats naturally infected with Microsporum canis in an annex facility: an open field trial

Dermatophytosis is the most common contagious and infectious skin disease of cats. It is of particular importance in animal shelters because it is a known zoonosis, highly contagious, and easily transmitted. In this open clinical trial, 58 cats with confirmed Microsporum canis dermatophytosis and 32 uninfected bonded pairs or littermates were treated with a combination of 21 days of oral itraconazole (10 mg kg(-1)) and twice weekly lime sulphur rinses until cured. Cats were not clipped in this treatment programme. Fungal cultures were obtained once weekly on all cats, and cats were considered cured when they had two consecutive negative weekly fungal cultures. Cats were held in the facility and received continued topical treatment until the fungal cultures were finalized. None of the cats developed oral ulcerations as a result of grooming the lime sulphur rinses. Oral ulcerations only developed in cats with clinical signs associated with upper respiratory disease. None of the uninfected cats living in contact with infected cats became culture positive or developed skin lesions. When data were examined retrospectively and the number of days to finalize the cultures was subtracted (21 days) from the total number of days the cats were housed in the annex, the mean number of days of treatment required for cure was 18.4 +/- 9.5 SEM (range 10-49 days). Cats with more severe infections required longer therapy. In this shelter, the combination of oral itraconazole and topical lime sulphur rinses for the treatment of dermatophytosis was effective and safe.     

Isolation of Microsporum canis from the hair coat of pet dogs and cats belonging to owners diagnosed with M. canis tinea corporis

Microsporum canis has been frequently isolated from human cases of tinea capitis and tinea corporis. The infection may be acquired from infected animals with cutaneous lesions but also from asymptomatic carriers or from the environment. As asymptomatic M. canis carriers are considered to be a critical factor in the epidemiology of dermatophytosis in humans, this study investigated the relationship between the presence of dermatophytes on the hair coats of dogs and cats without cutaneous lesions and the occurrence of the disease in their respective owners. A total of 136 dogs and 248 cats were sampled from January 1999 to January 2005. Seventy-eight animals (22 dogs and 56 cats) belonged to individuals affected by tinea corporis caused by M. canis and 306 (114 dogs and 192 cats) to individuals without dermatophytosis. Age, sex, breed, habitat and season were recorded for each animal and examined as potential risk factors. Dermatophytes were isolated from 20.5% of the dogs and 28.2% of the cats. Microsporum canis was isolated from 36.4% of dogs cohabiting with owners diagnosed with tinea corporis but it was never isolated from dogs whose owners had no lesions. By contrast, M. canis was isolated from 53.6% of cats cohabiting with owners diagnosed with tinea corporis and from 14.6% of cats whose owners had no signs of the disease. These results clearly indicate that both cats and dogs should be considered as a major source of pathogenic dermatophytes for humans even when they do not present clinical signs of dermatophytosis.     

FC‐1 Comparative efficacy of lufenuron and itraconazole in a guinea pig model of cutaneous Microsporum canis

During the last few years, reports have appeared claiming that lufenuron diminished or even cured dermatophyte infections in cats and dogs. As these observations have a rather anecdotal character leading to some ambiguity in the literature, it was decided to test lufenuron in a generally accepted animal model for dermatomycotic infection. The test was carried out in guinea pigs artificially infected with Microsporum canis on scarified dorsal skin and orally treated with lufenuron (Program?). The efficacy of up to five doses of 80 mg/kg was assessed 7 and 14 days after the start of treatment. All animals failed to show any improvement in skin lesions as compared to the vehicle‐only treated animals. Clinical symptoms taken into account were scaling, crust formation, erythema, and exudation. Neither the number of treatments (one or five) nor the dose range (40 or 80 mg/kg) made any difference. Itraconazole, tested earlier under identical circumstances, resulted in a clear and consistent improvement at day 7 of the infection at a dose of 15 mg/kg, given either in one dose or spread over several days. The absence of antimycotic activity of lufenuron in this established animal model constitutes a significant element in the discussion on the antifungal potency of lufenuron and supports the fact that there is, as yet, no evidence that benzoylphenyl urea derivative compounds have an effect on chitin synthesis in fungi. Funding: J&J Pharmaceutical Research and Development, Janssen Animal Health.     

A study of the efficacy of topical and systemic therapy for the treatment of feline Microsporum canis infection.

Microsporum canis infection was induced in 21 healthy SPF-derived cats. Once infection was established (4 weeks after inoculation) the cats were divided into three equal groups housed in separate rooms and monitored for 16 weeks. During this time, group A cats received oral griseofulvin at approximately 50 mg/kg daily and were shampooed twice weekly with a product containing chlorhexidine and miconazole. Group B cats were treated with griseofulvin alone, and group C cats served as untreated controls. The cats were examined on a weekly basis and the severity of lesions was scored semi-quantitatively. In addition, hair samples were collected from each cat on a weekly basis by the MacKenzie brush technique and by the sticky-tape method. A semi-quantitative scoring system was also used for the assessment of fungal (M canis) growth. Generally, significant differences in clinical scores were not seen between the groups although at weeks 3, 4 and 11 there was a significant difference (P< or =0.015) with cats in group A having significantly lower median scores than those in group C. Median times to clinical resolution (return of clinical scores to zero) in groups A, B and C were at treatment weeks 2, 9 and 12, respectively (P>0.05). Median times for mycological resolution (persistently negative culture results) for groups A, B and C were at treatment weeks 2, 9 and 12, respectively, for the MacKenzie brush technique and at weeks 4, 8 and 12 for the sticky-tape technique. For both these results, the groups differed significantly (P< or =0.001) and in both instances group A had significantly more rapid resolution than groups B or C. Median culture scores were significantly different between the three groups using one or both of the sampling techniques at week 2 through to week 12 of treatment with median scores for either group A alone, or groups A and B being significantly lower than group C (P< or =0.026). These results showed a benefit from the addition of twice-weekly chlorhexidine-miconazole shampooing to systemic griseofulvin therapy alone in the treatment of M canis infected cats.     

Use of itraconazole and either lime sulphur or Malaseb Concentrate Rinse® to treat shelter cats naturally infected with Microsporum canis: an open field trial

In an open non‐randomized study, 90 cats with severe dermatophytosis were treated with 21 days of oral itraconazole at 10 mg/kg and one of three topical antifungal rinses applied twice weekly: lime sulphur (LSO); reformulated lime sulphur with an odour‐masking agent (LSR); or a 0.2% miconazole nitrate and 0.2% chlorhexidine gluconate rinse (MC). Weekly examinations and fungal cultures were used to monitor the cats’ response to therapy. If at day 42 of treatment cats were still strongly fungal culture positive and/or developing new lesions, they were retreated with oral itraconazole and LSO. Cats were not prevented from licking the solutions and none developed oral ulcerations. Thirty‐one cats were treated with LSO, 27 with LSR and 32 with MC. The median number of days to cure was 30 (range 10–69 days) and 34 (range 23–80 days) for LSO and LSR, respectively. Thirty‐two cats were treated with MC, and 13 of 32 cats required repeat treatment because of persistent culture‐positive status and development of new lesions. Median number of days of treatment for the 19 cats that cured with MC was 48 (range 14–93 days). When the number of days to cure was compared between the groups, there was a significant difference between cats treated with LSO and LSR (P = 0.029) and cats treated with LSO and MC (P = 0.031), but no significant difference between the number of days to cure for cats treated with LSR and MC (P = 0.91).     

Use of isolated infected spores to determine the sporocidal efficacy of two commercial antifungal rinses against Microsporum canis

In this study, isolated infective Microsporum canis spores were used in an in vitro test model to compare the sporocidal activity of two commercial topical antifungal rinses. The two commercial test solutions used in the study were a lime sulphur solution 97.8% (LymDyp) and miconazole base 5.2%/chlorhexidine gluconate 5.9% mixture (Malaseb Concentrate Rinse). Water and household bleach were used as controls. Isolated infective spores were harvested from infected hairs and 500 microL of the spore suspension was incubated with an equal volume of dilutions of lime sulphur or the miconazole/chlorhexidine gluconate combination for 5 min and 4 h followed by fungal culture. There were too many to count colonies on the water control plates. Lime sulphur was 100% sporocidal at all test dilutions at both times. Miconazole/chlorhexidine gluconate was 100% sporocidal at all but the 1 : 128 dilution after 5 min of incubation and 100% sporocidal when incubated with spores for 4 h. It is not known if the two products have similar antifungal activity against infective spores on or within hairs; however, based on the findings of this study there is good evidence to recommend either rinse as an adjuvant topical therapy in a dermatophyte treatment and control program.