An Outbreak of Lymphocutaneous Sporotrichosis among Mine-Workers in South Africa

Background The 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. Methodology Employees 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 Findings Of 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.
Author Summary Sporotrichosis is a neglected tropical fungal disease. The subcutaneous form occurs following traumatic inoculation of organic matter contaminated with the fungus through the skin. Between 1938 and 1947, the Witwatersrand gold mines in South Africa were the site of the largest outbreak of sporotrichosis worldwide. Contamination of untreated timber by the fungus was thought to be associated with the outbreak though this epidemiologic link was never made definitively. For the first time in this setting, we conducted a detailed outbreak investigation to identify factors associated with sporotrichosis. The investigation identified 17 cases of sporotrichosis at a reopened South African gold mine. Approximately one in five miners had probable or confirmed sporotrichosis. Although genetically distinct species were isolated from clinical and environmental sources, it is highly 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. The investigation uncovered a re-emerging disease in mines where traditional, rather than heavily mechanized, ore extraction techniques are used. Surveillance should be instituted at sentinel mining locations.