Candida albicans in Faeces of Migratory Geese Can Persist in Agricultural Soils: One-Health Implications for Grazing Livestock

Abstract

The World Health Organization has classified five species of Candida as pathogens of critical concern on its recent 'Fungal Pathogen Priority List'. Candida albicans is the most common species aetiologically associated with human and animal mucosa; however, we know almost nothing about the environmental survival and the transfer pathways of C. albicans in natural environments. Here, we have isolated C. albicans from the faeces of newly arrived migratory geese in two agricultural fields in Scotland (the United Kingdom). All 14 confirmed isolates were characterised in terms of their pathogenicity (in a Galleria larval infection model) and resistance to four classes of antifungal drugs. Multilocus sequence typing (MLST) was used to assess the relatedness of these isolates with C. albicans isolated from the faeces of sheep grazing in the same field. Finally, mesocosms were used to test whether C. albicans in geese faeces could persist and remain viable when incorporated into agricultural soils. All C. albicans isolates were virulent, and exhibited resistance to at least one of the four classes of antifungal drugs against which they were screened. Maximum likelihood phylogenetic analysis of MLST sequences revealed that C. albicans isolated from goose and sheep faeces were relatively conserved, although they did cluster independently on separate clades. C. albicans remained viable in common agricultural soils, and after 60 days, the concentrations of all three representative C. albicans isolates had only declined by one log. The unrestricted movement of migratory birds provides a significant opportunity for the widespread dissemination of pathogens. Although C. albicans is not generally considered to be zoonotic, its introduction into new environments and subsequent persistence in agricultural systems has the potential to facilitate transmission between animal species or humans. Therefore , it is critical that more emphasis be put on monitoring animal migration and the potential for cross-boundary movement of pathogens, particularly with climate change widening the geographic range for pathogen persistence.