Sporotrichosis spp
From Felipedia
Sporotrichosis is a sporadic chronic granulomatous skin disease of humans and various domestic and laboratory animals caused by a fungal infection with Sporothrix schenckii. The organism is dimorphic and forms mycelia on vegetation and in Sabouraud’s dextrose agar at 25-30°C but is yeast-like in tissue and media at 37°C. It is ubiquitous in soil, vegetation, and timber; is distributed worldwide; and in the USA is most commonly found in coastal regions and river valleys. Infection usually results from direct inoculation of the organism into skin wounds via contact with plants or soil or penetrating foreign bodies[1].
The mycotic agent of sporotrichosis has 2 important mechanisms through which its potential to infect the mammalian host is maximized. First, S schenckii has the ability to change phases to an ascomycete telemorph that survives on living or decaying plant material. This fungus has been isolated from decaying vegetation such as thorns, straw, hay, wood, moss, and soil. Second, after entering the skin via puncture, bite, or scratch, the fungus converts to a yeast phase, thereby causing lesions locally and possibly systemically in the mammalian host. Sporothrix schenckii survives in the environment and becomes pathogenic in animals as a result of the dimorphic abilities of the organism; this dimorphism is the conversion from a yeast-like form at temperatures between 35 and 37°C to a mycelial phase (with branching, septate hyphae) at environmental or laboratory temperatures of 25 to 30°C. Environmental isolates of S schenckii will form hyphal mycelia but readily convert to a yeast-like form following injection into mice or other susceptible mammalian hosts. On the other hand, the yeast-like form identified in the lesions of animals is easily adapted to growth in hyphal-conidial form on suitable media incubated at 25 to 30°C. Some strains of S schenckii grow best at temperatures no higher than 35°C; these strains are believed to be involved in development of localized (fixed) cutaneous lesions in humans and animals[2][3].
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Zoonosis
Disseminated disease caused by inhalation of spores is rare. Sporotrichosis has been reported in dogs, cats, horses, cows, camels, dolphins, goats, mules, birds, pigs, rats, armadillos, and humans. Zoonotic infections can occur. The cat may be the species with the greatest zoonotic potential, and transmission from cat to human has been reported without evidence of trauma. In contrast, transmission from other infected species appears to require inoculation of previously traumatized skin. The large number of organisms shed from the wound and in the faeces of infected cats is believed to be responsible for the increased zoonotic potential of feline sporotrichosis[4].
Increasing attention is being focused on the role of domestic cats in the transmission of S. schenckii to humans. Zoonotic transmission of sporotrichosis has been documented, and this mechanism of infection could become more prevalent in populations of immunosuppressed individuals as suggested by reports of sporotrichosis in AIDS patients. Sporothrix schenckii has been listed as an emerging zoonotic disease. Six important factors that influence the emergence of zoonotic diseases have been identified; these include the transportation of humans and animals between geographic locations, increased contact between animals and humans, changes in the environment and husbandry practices, a growing population of immunocompromised humans, increased awareness of the zoonotic origin of many diseases, and the identification of organisms that were not previously known[5][6].
Clinical signs
Sporotrichosis may be grouped into 3 forms—lymphocutaneous, cutaneous, and disseminated. The lymphocutaneous form is the most common. Small, firm dermal to subcutaneous nodules, 1-3 cm in diameter, develop at the site of inoculation. As infection ascends along the lymphatic vessels, cording and new nodules develop. Lesions ulcerate and discharge a serohemorrhagic exudate. Although systemic illness is not seen initially, chronic illness may result in fever, listlessness, and depression. The cutaneous form remains localized to the site of inoculation, although lesions may be multicentric. Disseminated sporotrichosis is rare but potentially fatal and may develop with neglect of cutaneous and lymphocutaneous forms. Infection develops via hematogenous or tissue spread from the initial site of inoculation to the bone, lungs, liver, spleen, testes, GI tract, or CNS. In humans, the incidence of systemic sporotrichosis appears to be rising, primarily due to infection of immunocompromised people.
Diagnosis
Diagnosis can be made by cultural (samples obtained from unopened lesions) or microscopic examination of the exudate or biopsy specimens. In tissues and exudate, the organism is present as few to numerous, cigar-shaped, single cells within macrophages. The fungal cells are pleomorphic and small (2-10 × 1-3 µm); buds may be present and give the appearance of a ping-pong paddle. A fluorescent antibody technique has been used to identify the yeast-like cells in tissues. In species other than cats, Sporothrix organisms are often sparse in exudate and infected tissue so that diagnosis usually requires culturing the organism. In cultures, a true mycelium is produced, with fine, branching, septate hyphae bearing pear-shaped conidia on slender conidiophores.
Sporotrichosis is a fungal infection caused by a fungus called Sporothrix schenckii. It usually infects the skin. The fungus can be found in sphagnum moss, in hay, in other plant materials, and in the soil. It enters the skin through small cuts or punctures from thorns, barbs, pine needles, or wires. It can also be inhaled and cause pulmonary infection or disseminated infection in cats. It is not spread from person to person[7].
Treatment
Itraconazole is the preferred treatment for cutaneous and lymphocutaneous sporotrichosis. It may also be used to treat bone and joint infections. Itraconazole is administered orally to cats at dosages of 5 to 10 mg/kg (2.3 to 4.5 mg/lb) every 12 hours, preferably with food that increases absorption. Compared with the capsule formulation (at an equivalent dose), the liquid form of itraconazole is often used to treat cats because it permits more accurate dose measurement, is best absorbed when food has been withheld, and attains higher peak plasma concentrations. Few adverse effects associated with the use of itraconazole in cats have been reported; in 1 study,26 no adverse effects were detected in cats treated orally with 10 mg/kg/d for 3 months, whereas cats treated with the same dosage of ketoconazole developed anorexia and weight loss. Administration of any imidazole (including itraconazole) is contraindicated during pregnancy. In cats treated with antifungal agents, drug toxicoses have been reported and necessitate that serum biochemical analyses are performed regularly during treatment of sporotrichosis. Treatment should be continued for 1 month after apparent clinical cure to prevent recurrence of clinical signs[8].
For patients with severe disease, and/or pulmonary, central nervous system or disseminated infection, a lipid formulation of amphotericin B should be used initially. Potassium iodide is another option for cutaneous or lymphocutaneous disease that does not respond to itraconazole.
References
- ↑ Dunstam, R.W.; Langham, R.F; Reimann, K.A.; Wakenel, P.S. Feline sporotrichosis: a report of five cases with transmission to humans Journal of American Academy of Dermatology, v. 15, p. 37-45, 1986.
- ↑ Nusbaum, B.P.; Gulbas, N.; Horwitz, S.N. Sporotricosis acquired from a cat. Journal of American Academy of Dermatology, v.8, p. 386-91, 1983
- ↑ [1]
- ↑ Read, S.I. & Sperling, L.C. Feline sporotrichosis acquired from a cat Journal of American Academy. of Dermatology,v. 8, p. 386-91, 1983
- ↑ Zamri-Saad, M.; Salmiyah, T.S.; Jasni, S.M.; Cheng, B.Y.; Basri, K. Feline sporotrichosis: an increasingly important zoonotic disease in Malaysia. Veterinary Record.,v. 127, p. 480, 1990
- ↑ AVMA.org
- ↑ CDC.gov
- ↑ [2]
