Revisiting Sapronoses Through Aspergillosis

Zoonoses are generally defined as infections that are naturally transmitted between humans and other vertebrate animals. Among fungi, dermatophytes are well-established zoonotic pathogens. In contrast, many pathogenic molds are environmental saprophytes, with infections typically resulting from the direct uptake of fungal propagules-such as airborne spores-from soil, decaying organic matter, or other non-living reservoirs. Rather than being transmitted between animals and humans, these infections originate from environmental sources. In 1958, Terskikh introduced the term "sapronosis" (or "saprozoonosis") to describe such infections acquired from the environment rather than from other living hosts. In 2003, Hubálek expanded on this concept, providing a comprehensive list of major sapronoses and their causative agents, including Aspergillus fumigatus, the primary cause of aspergillosis. Aspergillosis is a fungal disease caused by species of the genus Aspergillus, typically acquired through inhalation of airborne spores from soil and other external environments. Although the environmental transmission of Aspergillus spp. has long been recognized, recent changes in human living environments, evolving animal husbandry practices, and global ecological shifts-including climate change and the human-mediated dispersal of pathogenic organisms-highlight the need to re-evaluate these fungi as sapronotic agents. In this review, we revisit the concept of sapronosis using aspergillosis as a representative example, drawing on investigations conducted in collaboration with colleagues involving penguins housed in zoos and aquariums and the characteristics of their captive environments. Through these studies, we aim to explore the implications of environmental fungal exposure for both human and animal health.