Abstract
BackgroundThe largest outbreak of sporotrichosis occurred between 1938 and 1947 in the gold mines of Witwatersrand in South Africa. Here, we describe an outbreak of lymphocutaneous sporotrichosis that was investigated in a South African gold mine in 2011.MethodologyEmployees working at a reopened section of the mine were recruited for a descriptive cross-sectional study. Informed consent was sought for interview, clinical examination and medical record review. Specimens were collected from participants with active or partially-healed lymphocutaneous lesions. Environmental samples were collected from underground mine levels. Sporothrix isolates were identified by sequencing of the internal transcribed spacer region of the ribosomal gene and the nuclear calmodulin gene.Principal FindingsOf 87 male miners, 81 (93%) were interviewed and examined, of whom 29 (36%) had skin lesions; specimens were collected from 17 (59%). Sporotrichosis was laboratory-confirmed among 10 patients and seven had clinically-compatible lesions. Of 42 miners with known HIV status, 11 (26%) were HIV-infected. No cases of disseminated disease were detected. Participants with ≤3 years’ mining experience had a four times greater odds of developing sporotrichosis than those who had been employed for >3 years (adjusted OR 4.0, 95% CI 1.2–13.1). Isolates from 8 patients were identified as Sporothrix schenckii sensu stricto by calmodulin gene sequencing while environmental isolates were identified as Sporothrix mexicana.Conclusions/Significance S. schenckii sensu stricto was identified as the causative pathogen. Although genetically distinct species were isolated from clinical and environmental sources, it is likely that the source was contaminated soil and untreated wood underground. No cases occurred following recommendations to close sections of the mine, treat timber and encourage consistent use of personal protective equipment. Sporotrichosis is a potentially re-emerging disease where traditional, rather than heavily mechanised, mining techniques are used. Surveillance should be instituted at sentinel locations.
Highlights
Sporotrichosis is a subcutaneous mycosis that usually occurs following traumatic inoculation of organic matter contaminated with thermally-dimorphic fungi within the Sporothrix schenckii species complex [1]
Further work revealed three new closely-related cryptic species that were distinct from S. schenckii sensu stricto by phylogenetic analysis of the CAL gene: the hyper-virulent Sporothrix brasilensis, Sporothrix globosa and a third species that was initially only isolated from the environment and has more recently been isolated from human and animal cases, Sporothrix mexicana [8]
Identification of fungal isolates that resembled S. schenckii by phenotypic methods was confirmed by sequencing of the internal transcribed spacer (ITS) region of the ribosomal gene, which allowed identification to the species complex level, and sequencing of the nuclear CAL gene, which allowed the isolates to be identified to the cryptic species level [7,9]
Summary
Sporotrichosis is a subcutaneous mycosis that usually occurs following traumatic inoculation of organic matter contaminated with thermally-dimorphic fungi within the Sporothrix schenckii species complex [1]. In South Africa, approximately 3300 miners were clinically diagnosed with sporotrichosis between 1938 and 1947 on the Witwatersrand [2,3,4]. Contamination of timber by the fungus was thought to be associated with the outbreak and S. schenckii sensu lato was not cultured from environmental sources despite several attempts (4). Further work revealed three new closely-related cryptic species that were distinct from S. schenckii sensu stricto by phylogenetic analysis of the CAL gene: the hyper-virulent Sporothrix brasilensis, Sporothrix globosa and a third species that was initially only isolated from the environment and has more recently been isolated from human and animal cases, Sporothrix mexicana [8]. The largest outbreak of sporotrichosis occurred between 1938 and 1947 in the gold mines of Witwatersrand in South Africa. We describe an outbreak of lymphocutaneous sporotrichosis that was investigated in a South African gold mine in 2011
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