Dermatology Online Journal

Cat-transmitted cutaneous lymphatic sporothricosis
Marcus Henrique de S B Xavier MD, Amanda de Lima Teixeira MD, Jane Marcy N Pinto PhD, Karla Strong Rodrigues MD, Enoi Guedes Vilar PhD, Ângela Cristina L Souza MD, Gabriela Blatt Pereira MD
Dermatology Online Journal 14 (7): 4

Universidade Federal Fluminense, Hospital Universitário Antônio Pedro - Serviço de Dermatologia. Niterói, Rio de Janeiro, Brazil. marcus_hx@hotmail.com

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Abstract

Sporotrichosis is the most common of the deep mycoses. In most cases the transmission occurs secondary to recent penetrating trauma with plant thorns, wood splinters or contaminated organic material. We report a case of a 68-year-old Brazilian female with a small ulcer on her right forefinger and palpable erythematous nodules on her right forearm. These occurred after the bite of a domestic cat that had a lesion on its hind-foot. Since the 1980s, the role of felines in the transmission of this mycosis to humans has gained attention among animal owners, veterinarians, and caretakers. Humans can be contaminated by a cat scratch or bite and even by contact with contaminated solutions.

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Clinical Synopsis

A 68-year-old Brazilian housewife from the Rio de Janeiro metropolitan area presented with a 2-week history of the development of a small ulcer on her right forefinger and palpable erythematous nodules on her right forearm. Her illness had begun as a forefinger pustule about 4 weeks prior to presentation. This began after a bite from a domestic cat that had a lesion on its hind-foot. The patient had taken an antibiotic (cephalexin) without any improvement. Her medical history was unremarkable.

Figure 1	Figure 2

On physical examination, the patient presented with an ulcer that measured 1cm in diameter with erythematous borders on her right forefinger. Subcutaneous erythematous nodules extended in a linear and ascending distribution on her right hand (Fig. 1) and forearm (Fig. 2). The results of chest x-ray, blood chemistry, blood count and urinalysis were within normal limits.

Figure 3a	Figure 3b

Biopsy specimens from the patient were obtained for histological examination (Figs. 3a & 3b) and culture (bacterial and mycology). The biopsy showed an inflammatory infiltrate with a characteristic arrangement of a central neutrophilic suppuration, surrounded by a tuberculoid granuloma. The epidermis had pseudoepitheliomatous hyperplasia.

The bacterial culture was negative. The fungal culture, performed at 25°C using Sabouraud dextrose agar for 5 days, showed a creamy white colored colony. Microscopy demonstrated conidia displaying a bouquet configuration, which was compatible with Sporothrix schenckii (Fig. 4).

The diagnosis of lymphocutaneous sporotrichosis was made. The patient was treated with potassium iodide 4.5g/daily divided in 3 doses and after 5 months of treatment her lesions were completely cleared and there was no recurrence upon examination 13 months later.

Discussion

Sporotrichosis is the most common of the deep mycoses and is characterized by the subacute and chronic evolution of cutaneous or subcutaneous nodular lesions [1]. The etiological agent Sporothrix schenckii is a dimorphic fungus, existing in a mycelial phase and a yeast phase. Yeast is the infective form and this phase is pleomorphic, showing spindle-shaped and oval cells [2]. In most cases the transmission occurs after recent penetrating trauma with plant thorns, wood splinters or contaminated organic material [1].

Since the 1980s, the role of felines in the transmission of this mycosis to humans has gained attention among animal owners, veterinarians and caretakers [3]. Humans can be contaminated by cat's scratch or bite and even by contact with contaminated materials and liquids [4].

Acquired human sporotricosis from a sick cat exhibits no differences from ordinary human sporotrichosis. Patients have been observed with the usual lymphangitic or fixed cutaneous form. In contrast, feline sporotrichosis tends to disseminate, leading to the death of the animal. The most common presentation is an ulcerative skin lesion on the head and limbs [4].

Schubach et al. (2005) evaluated 148 cats with sporotrichosis for the presence of the S. schenckii [4]. The fungus was isolated from 100 percent of the cutaneous lesions, 47 percent of nasal cavity swabs, 33 percent of oral cavity swabs and 15 percent of nail fragment pools. S. schenckii was isolated from the oral and nasal cavities of 10 out of 101 apparently healthy cats that lived with others cats exhibiting clinical sporotrichosis.

Souza et al. (2006) evaluated the frequency of Sporothrix schenckii in the nails of 24 healthy cats living together with cats showing clinical sporotrichosis [5]. The fungus was isolated from 7 cats. This result demonstrates the importance of asymptomatic carriage in cats in the transmission of the sporotrichosis. Possibly due to the large number of fungal elements typical in felines tissues, the transmission to man can occur even in the absence of a history of trauma [6].

Although sporotrichosis may be suggested by the presence of fungal structures in tissues or exudates by direct examination, the definitive diagnosis of Sporothrix schenckii infection requires isolation of the organism in culture at 25°C and its conversion to yeast-like form at 37°C [6].

There has been an epidemic of cat-transmitted sporotrichosis in Rio de Janeiro, Brazil since 1998. In vitro studies have shown the MIC values for amphotericin B, itraconazole, and terbinafine to be lower for isolates of sporotrichosis associated with the epidemic than other strains [7]. The treatment of choice for lymphcutaneous sporotrichosis is itraconazole. Typically, 100mg BID is given PO in adults; the dose may be increased if there is no satisfactory response. The effective length of treatment has been documented at 3-6 months [8]. Although pediatric use has not been fully approved with established dosing, this drug has also been used as the drug of choice in pediatric patients in the Brazilian outbreak [9]. Pulse itraconazole has been successful in a small trial in adults in Mexico [10]. Itraconazole was given PO at 400mg per day for one week followed by a 3-week break. Repeated similar pulses were given until clinical and mycological cure was shown. The mean number of pulses required was 3.5. Fluconazole may be used at 400mg PO every day in adults. The pediatric dose is 3-6 mg per kg per day (6-12 mg/kg for severe infections) [11]. Terbinafine has been used with success in adults at 250mg BID to 500mg BID. The comparative efficacy of the 2 different doses has been evaluated head to head [12]. The cure rate was higher in the treatment group that received 1000 mg per day. In this group, 87 percent of patients achieved cure by 24 weeks of treatment and there were no relapses after 24 weeks of follow up. SSKI treatment is also effective. Typically, 300-500mg (6-10gtt) PO TID is the adult dose. Our patient was unable to afford treatment with itraconazole due to cost, but responded well to SSKI. The treatment of the illness transmitted by felines appears to be no different than other cases of sporotrichosis. On the other hand, the treatment of the cat is more complex because they are more susceptible to potassium iodine toxicity and there are no reliable results on the use of cetoconazole, itraconazole or fluconazole [4].

References

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