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Molecular detection of Histoplasma capsulatum in environmental samples collected from South African caves

Summary

Researchers tested soil and guano samples from seven South African caves and found evidence of Histoplasma capsulatum fungus in five of them using molecular detection methods. This fungus causes a respiratory disease called histoplasmosis and is released into the air when cave soil is disturbed. The findings confirm that cave explorers, speleologists, and guano miners visiting these caves should wear protective masks or respirators to avoid infection.

Background

Histoplasma capsulatum naturally occurs in cave soil enriched by bat guano and is a known source of exposure for cave explorers. South African caves have been documented as probable sources of infection with several outbreaks of acute pulmonary histoplasmosis reported since 1977, though environmental detection has not been confirmed.

Objective

To use molecular assays to detect and confirm the presence of H. capsulatum in environmental samples collected from regularly-explored South African caves.

Results

H. capsulatum was detected in 18 of 56 samples (32%) from five of seven caves using RT-qPCR or Hc100 PCR assays. Both assays were positive in 21% of samples, while 7% were only RT-qPCR positive and 4% only Hc100 PCR positive. No samples tested positive with the ITS PCR assay. Phylogenetic analysis identified four distinct groups clustering with South African clinical isolates.

Conclusion

H. capsulatum is present in several regularly-explored South African caves with bat populations. The RT-qPCR and Hc100 PCR assays are useful tools for environmental surveillance. Protective measures such as wearing masks or respirators should be implemented when entering contaminated caves, especially during activities disturbing guano.
  • Published in:PLoS Neglected Tropical Diseases,
  • Study Type:Environmental surveillance study,
  • Source: 10.1371/journal.pntd.0013778, PMID: 41428709
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