Candida Infections in Marine Mammals: Epidemiology, Antifungal Resistance, and One Health Implications

Candida albicans is currently considered one of the most significant fungal pathogens in cetaceans and pinnipeds and the spread of antifungal-resistant strains pose significant threats to animal health and One Health concerns. Although C. albicans is the most commonly detected species, non-albicans Candida (NAC) species, including C. tropicalis, C. parapsilosis and Nakaseomyces glabratus and the multidrug-resistant C. auris, have been recognized in captive dolphins. This review examines the clinical patterns observed in marine mammal taxa: cetaceans are most commonly vulnerable to respiratory and disseminated mycoses owing to their distinct anatomical characteristics, whereas mucocutaneous infections are the common manifestation in pinnipeds. Localized mucocutaneous infections may progress to fatal systemic disease, with mortality rates approaching 100% in severe cases, despite therapeutic treatment. The most important predisposing factors are immunosuppression, long-term antibiotic treatment, environmental stress factors, and the deterioration of water quality. Diagnostic methods are based on cytology, histopathology, culture, and molecular methods, and treatment is mostly composed of systemic azole antifungals although with high levels of therapeutic failure. Recent results showed that there are high levels of azole resistance in the isolates of marine mammals that had no history of exposure to antifungal agents, which points to the role of aquatic environments as sources of resistance genes. The lack of knowledge remains particularly evident in species-specific pharmacokinetics and the development of evidence-based treatment guidelines. These infections also have broader implications for ecosystem health surveillance and the protection of endangered marine mammal populations. The current review highlights the One Health approach with marine mammals being at the core of ocean health surveillance and identifies the potential for zoonotic transmission.