Pigeon-Guano-Contaminated Environments in Blantyre, Southern Malawi, are Reservoirs of Medically Important Fungi

Close to 50% of all bird species are reservoirs of potentially pathogenic fungi, including species listed as priorities by the World Health Organization. In Malawi, data on the diversity, pathogenic potential, and avian ecological sources of medically important yeasts are scarce. A descriptive cross-sectional study was conducted to characterise medically important yeast recovered from environments contaminated with pigeon guano in Blantyre, Southern Malawi. A total of 20 pigeon guano samples were collected from 4 peri-urban areas, which yielded 71 yeast isolates. Only 54 isolates were successfully identified after VITEK MS analysis. More than 80% of the identified environmental isolates belong to fungal species listed as priority, with Pichia kudriavzevii (39%) and Candida orthopsilosis (30%) the most common species. Phenotypic comparisons of virulence traits: phospholipase activity, haemolysin activity, catalase, urease, biofilm formation, thermotolerance, and adhesion properties were made with 21 clinical yeast isolates from referral laboratories. Candida parapsilosis sensu stricto (29%) and Candida albicans (24%) constituted a majority of the clinical yeast isolates. Most of the environmental isolates exhibited virulence traits comparable to or stronger than those of clinical isolates, indicating an infection risk to humans and the urgent need for integrated, One Health-focused surveillance at bird-human interfaces.