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Infection caused by a cryptic fungal species, Blastomyces gilchristii, in a tiger

Summary

A tiger at a veterinary hospital developed a serious fungal infection that affected its brain and lungs. Using advanced DNA sequencing technology, researchers identified the infection was caused by a previously unrecognized fungal species called Blastomyces gilchristii. This discovery was important because it showed that this dangerous fungus exists in areas where scientists previously thought it wasn’t found, and it highlights the importance of using modern genetic testing to identify unusual infections.

Background

Blastomycosis is typically caused by Blastomyces dermatitidis, a thermally dimorphic fungus. Recent advances in sequencing have identified additional cryptic Blastomyces species capable of causing infections. This report describes the first documented case of B. gilchristii infection in a tiger in the southeastern USA.

Objective

To describe and characterize an infection caused by the cryptic fungal species Blastomyces gilchristii in an adult female tiger presenting with acute neurological signs.

Results

Histopathology revealed disseminated mycosis with encephalitis and pneumonia characterized by 15-25 µm yeasts with thick double-contoured walls and broad-based budding. Fungal isolate displayed atypical characteristics with inconclusive conventional PCR. Whole-genome sequencing identified the isolate as B. gilchristii with over 98% read mapping to the reference genome. Antifungal susceptibility testing showed MICs for fluconazole (2.0), itraconazole (≤0.03), posaconazole (0.06), and voriconazole (0.06).

Conclusion

This case represents the first documented B. gilchristii infection in a tiger and the first in the southeastern USA, suggesting a wider geographic distribution than previously reported. Whole-genome sequencing was essential for identifying this cryptic pathogen. The findings highlight the importance of molecular diagnostics in characterizing emerging fungal infections and understanding disease epidemiology.
  • Published in:Access Microbiology,
  • Study Type:Case Report,
  • Source: PMID: 40843027, DOI: 10.1099/acmi.0.001011.v3
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