Sporotrichosis

Sporotrichosis is caused by members of the fungal genus Sporothrix, which normally grow as saprophytes in the environment, and may be present on vegetation and in organic debris and soil. When fungal spores are accidentally inoculated into the skin (most often via sharp pieces of vegetation), some species of Sporothrix transform from filamentous molds into yeasts, and proliferate. In most cases, these organisms remain confined to the skin and lymphatics, causing relatively superficial lesions such as erythematous nodules, ulcers and plaques. Without treatment, these lesions may persist for months or years, or even indefinitely. Uncommonly, the organisms invade deeper tissues, including bone, joints and various internal organs, or disseminate widely in the skin. Disseminated infections, including rare instances of pulmonary sporotrichosis from inhaled organisms, can be life-threatening. While sporotrichosis can affect a wide variety of mammals, including humans, this disease is a particular concern in cats. Most mammals have only small numbers of organisms in sporotrichosis lesions, and transmission to other animals or people is unusual. However, these yeasts are often abundant in the lesions of cats. In 20022003, an epidemic of sporotrichosis emerged among free-roaming cats in impoverished urban areas of Rio de Janeiro, Brazil. The organism continues to spread between cats in this area, with several thousand cases reported as of 2017. Infected cats have also transmitted sporotrichosis to more than 4000 people and over a hundred dogs. Recently, feline epidemics have emerged in other resource-poor urban centers in southern Brazil.