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Despite the clinical relevance of major tuberculous pathogens to domestic animals and humans, the understanding of mycobacterial transmission modes, pathways, and interactions in their natural habitats remains very limited. The reason for this is primarily because ecological and evolutionary concepts have not yet been widely applied to the understanding of these bacteria. Most existing research on mycobacterial transmission is not founded on hypothesis testing but rather tends to accept the most recent explanation and turn it into a canonical fact. In this comparative review, we discuss plausible alternative hypotheses against a null hypothesis of environmental origin to intensify research on mycobacterial pathogens and their capacity to spread in the context of global change. We highlight a major bias in perceptions of mycobacterial infection transmission, with most work concentrating only on the contagious stage of tuberculous clones. We suggest broadening the field to include research on environmental non-tuberculous mycobacteria and their life histories. A deeper understanding of mycobacterial ecology and evolution is more important now than ever, considering the vast diversity of known and unknown mycobacterial species in natural ecosystems. Infectious disease medicine, veterinary science, and public health surveillance should take a more integrative disease ecology approach to enhance the development of new approaches for control of these animal and human pathogens. 

Pathogens such as bacteria, fungi and viruses are important components of soil and aquatic communities, where they can benefit from decaying and living organic matter, and may opportunistically infect human and animal hosts. One-third of human infectious diseases is constituted by sapronotic disease agents that are natural inhabitants of soil or aquatic ecosystems. They are capable of existing and reproducing in the environment outside of the host for extended periods of time. However, as ecological research on sapronosis is infrequent and epidemiological models are even rarer, very little information is currently available. Their importance is overlooked in medical and veterinary research, as well as the relationships between free environmental forms and those that are pathogenic. Here, using dynamical models in realistic aquatic metacommunity systems, we analyze sapronosis transmission, using the human pathogenMycobacterium ulceransthat is responsible for Buruli ulcer. We show that the persistence of bacilli in aquatic ecosystems is driven by a seasonal upstream supply, and that the attachment and development of cells to aquatic living forms is essential for such pathogen persistence and population dynamics. Our work constitutes the first set of metacommunity models of sapronotic disease transmission, and is highly flexible for adaptation to other types of sapronosis. The importance of sapronotic agents on animal and human disease burden needs better understanding and new models of sapronosis disease ecology to guide the management and prevention of this important group of pathogens. 

ABSTRACT Mycobacterium ulceranspseudoshottsiiis a mycolactone‐producing bacterium previously isolated from Striped Bass (Morone saxatilis(Walbaum)) from Chesapeake Bay and adjacent waters of the Atlantic Coast of North America. We report the first molecular detection of this pathogen in the native Gulf strain ofMorone saxatiliscollected from the Pearl River, Mississippi (USA). Molecular identification was conducted using a novel PCR assay targeting the parA‐625 intergenic spacer of the virulence‐associated pMUM plasmid. The isolate was unambiguously assigned toM. u. pseudoshottsiibased on diagnostic single nucleotide polymorphisms (SNPs) and phylogenetic analysis. This report expands the known range ofM. u. pseudoshottsiito include Gulf Coast watersheds and highlights the need for enhanced surveillance in wild and aquacultured fish populations of the southern United States. 

ABSTRACT Understanding the interactions of ecosystems, humans and pathogens is important for disease risk estimation. This is particularly true for neglected and newly emerging diseases where modes and efficiencies of transmission leading to epidemics are not well understood. Using a model for other emerging diseases, the neglected tropical skin disease Buruli ulcer (BU), we systematically review the literature on transmission of the etiologic agent, Mycobacterium ulcerans (MU), within a One Health/EcoHealth framework and against Hill's nine criteria and Koch's postulates for making strong inference in disease systems. Using this strong inference approach, we advocate a null hypothesis for MU transmission and other understudied disease systems. The null should be tested against alternative vector or host roles in pathogen transmission to better inform disease management. We propose a re-evaluation of what is necessary to identify and confirm hosts, reservoirs and vectors associated with environmental pathogen replication, dispersal and transmission; critically review alternative environmental sources of MU that may be important for transmission, including invertebrate and vertebrate species, plants and biofilms on aquatic substrates; and conclude with placing BU within the context of other neglected and emerging infectious diseases with intricate ecological relationships that lead to disease in humans, wildlife and domestic animals.