Cat-Transmitted Sporotrichosis: Epidemic in Brazil

Abstract & Commentary

Synopsis: Zoonotic transmission resulting from exposure to infected cats was responsible for an epidemic of 178 human cases of sporotrichosis in Rio de Janeiro, Brazil, from 1998 to 2001. Cats infected with sporotrichosis pose a significant risk of disease transmission to humans because of their extensive skin lesions and high burden of organisms. Patients seen during this epidemic received itraconazole as first-line treatment with more than a 90% cure rate.

Source: Barros MD, et al. Cat-transmitted sporotrichosis epidemic in Rio de Janeiro, Brazil: Description of a series of cases. Clin Infect Dis.2004; 38:529-535.

From 1998 to 2001, 178 cases of culture-proven sporotrichosis were diagnosed in the city of Rio de Janeiro and the surrounding municipalities. Most patients were female (68%), adults (70.8%), and involved in a domestic occupation. The majority of patients had either the fixed cutaneous or a lymphocutaneous form of the disease. None of the patients in the outbreak had pulmonary, osteoarticular, or disseminated sporotrichosis.

The diagnosis was made by culturing the fungus from secretions, biopsies, or aspirates of these lesions. As is often the case, the results of direct microscopic wet mount preparations were negative for almost all of the samples. However, fungal elements were detectable in 28.8% of the histopathological samples. The yeast forms are usually 4-6 mm in diameter and often described as oval to cigar-shaped.

A feline sporotrichosis epidemic coincided with the human epidemic. More than 90% of the patients reported either domestic or professional contact (ie, veterinarians) with infected cats. Many patients recalled a traumatic injury, such as a bite or scratch from a cat with sporotrichosis. Those patients who could not recall a traumatic injury often reported close contact with infected cats.

The majority of infected patients were treated with itraconazole 100 mg/d, with 8 patients requiring a dosage increase to 400 mg/d. Seven patients received other agents, such as potassium iodide and/or amphotericin B, in addition to itraconazole. One pregnant patient was treated only with heat therapy. In this epidemic, spontaneous remission, which is unusual, was noted in 13 patients.

Comment by Mary-Louise Scully, MD

Sporotrichosis is caused by Sporothrix schenckii, a dimorphic fungus that has a worldwide distribution. The organism grows well in the environment, particularly in sphagnum moss, decaying vegetation, soil, and hay. Persons exposed to these environmental foci are at risk for acquiring infection. Activities frequently associated with acquisition of sporotrichosis are rose gardening, topiary work (ornamental tree or shrub trimming), Christmas tree farming, hay baling, and masonry work.1

One of the largest human outbreaks of sporotrichosis occurred in Witwaterstrand, South Africa, from 1941-1944, when almost 3000 gold miners developed sporotrichosis after inoculation from splinters of contaminated timbers in the mines.2 The largest outbreak in the United States affected 84 patients in over 15 states, when conifer seedlings were packed in S schenckii infected sphagnum moss that originated in Wisconsin.3

However, an alternative mode of transmission for S schenckii is from the bites or scratches of animals. Animals most often associated with zoonotic transmission of sporotrichosis have been armadillos and cats. Armadillos do not seem to be infected with the organism but transmit infection to humans through nail scratches, especially while attempting to evade capture. Cats, however, can develop serious and sometimes fatal sporotrichosis. Infected cats are thought to pose a considerable risk of transmission to humans because the cats often have extensive, ulcerative skin lesions with a heavy burden of organisms. In one study, S schenckii was isolated from 100% of skin lesions, 66% of nasal cavities, and 39% of the nails of infected cats.4 Normal cat behavior often involves rubbing against their owners and handlers, with unintentional scratching and biting. In 15 of these Brazilian cases, molecular typing confirmed the relationship between the patient strains of S schenckii and that of their cat.

The most common manifestation of infection with S schenckii is a primary cutaneous lesion that usually begins as a papule, enlarges to become nodular, and often ulcerates. This initial lesion can persist alone (fixed or localized cutaneous), or progress further to nodular lesions appearing along the proximal lymphatics (lymphocutaneous form). Disseminated visceral, osteoarticular, meningeal, or pulmonary sporotrichosis can occur, but typically are associated with host risk factors such as alcoholism, diabetes mellitus, chronic obstructive pulmonary disease, and HIV infection.

Most would agree that all forms of sporotrichosis warrant treatment, most often with antifungals. The spontaneous remission of infection noted in 13 patients in this study is unusual and very rarely reported in the literature. Saturated solution of potassium iodide (SSKI), which does not kill this organism, was the traditional therapy for cutaneous sporotrichosis since the beginning of the 20th century. However, side effects such as nausea, metallic taste, fever, rash, and salivary swelling have led to the use of itraconazole as the drug of choice for cutaneous and lymphocutaneous sporotrichosis. The success rate is 90-100% when itraconazole is used at 100-200 mg daily for 3 to 6 months. Fluconazole is not as effective as itraconazole, and if used at all, the dose should be at least 400 mg/d.5

Local measures, such as heat, for treatment of cutaneous sporotrichosis have been used. The basis for this treatment regimen originates from the observation that some strains of S schenckii exhibit growth inhibition at temperatures greater than 35°C. Local heat therapy, as used by the pregnant patient in this study, may be an option for patients with a single cutaneous lesion, but it requires faithful application of heat for at least an hour daily for several months. Azoles and SSKI are both contraindicated in pregnancy. It is quite acceptable to delay treatment of cutaneous sporotrichosis until after the pregnancy, since there is no risk of the infection disseminating to the fetus, and no evidence that the disease is worsened by pregnancy.

References

1. Kaufman CA. Sporotrichosis. Clin Infect Dis. 1999;29:231-237.

2. Lurie HI. Five unusual cases of sporotrichosis from South Africa showing lesions in muscles, bones, and viscera. Br J Surg.1963;50:585-591.

3. Dixon DM, et al. Isolation and characterization of Sporothrix schenckii from clinical and environmental sources associated with the largest U.S. epidemic of sporotrichosis. J Clin Microbiol.1991;29:1106-1113.

4. Schubach TM, et al. Sporothrix schenckii isolated from domestic cats with and without sporotrichosis in Rio de Janeiro, Brazil. Mycopathologia.2002;153:83-86.

5. Kaufman CA, et al. Practice guidelines for the management of patients with sporotrichosis. Clin Infect Dis. 2000;30:684-687.

Mary-Louise Scully, MD, Sansum-Santa Barbara Medical Foundation Clinic, Santa Barbara, California, is Associate Editor of Travel Medicine Advisor.