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First isolation of Prototheca bovis from a bottlenose dolphin (Tursiops truncatus)

Summary

A 13-year-old bottlenose dolphin at a Japanese aquarium developed a stomach infection caused by Prototheca bovis, a type of alga rarely found in marine animals. The dolphin initially received treatment with itraconazole for a suspected fungal infection, but this was ineffective. When doctors identified the actual culprit as P. bovis through genetic testing, they switched to fos-ravuconazole, which successfully resolved the infection and returned the dolphin to good health.

Background

Prototheca species are achlorophyllic algae found in the environment and animal intestines that can cause protothecosis in humans and animals. P. wickerhamii and P. bovis are most commonly associated with disease, but little is known about their pathogenicity in marine animals. This is the first reported case of Prototheca isolated from a dolphin’s digestive tract.

Objective

To report and characterize the first isolation of Prototheca bovis from the digestive tract of a bottlenose dolphin presenting with clinical symptoms of infection.

Results

P. bovis was isolated and identified with 100% sequence identity to the type strain. The isolate showed MIC values of 1 μg/ml for itraconazole and 0.06 μg/ml for ravuconazole. Treatment with fos-ravuconazole resulted in resolution of symptoms and cessation of P. bovis isolation, while itraconazole alone was ineffective. The dolphin recovered normal body temperature and improved condition after 26 days of fos-ravuconazole treatment.

Conclusion

This case represents the first documented isolation of P. bovis from a dolphin and suggests opportunistic protothecosis may occur in marine mammals. Ravuconazole demonstrated superior efficacy compared to itraconazole for treating this infection. Further investigation into the ecology of Prototheca in marine environments and epidemiology in marine mammals is warranted under a One Health approach.
  • Published in:Medical Mycology Case Reports,
  • Study Type:Case Report,
  • Source: PMID: 41257268, DOI: 10.1016/j.mmcr.2025.100746
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