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Zoonotic emergence requires spillover from animals to humans, hence animal-human interactions. A lot has been emphasized on human intrusion into wild habitats (e.g., deforestation, hunting) and the development of agricultural and farming activities. However, the highly human-modified urban and peri-urban socio-ecosystems are also of great concern due to huge amounts of pet, domesticated and wild animals (e.g., birds, rodents and bats) that live in very close contact to very dense human populations. This adds to the existence of wet wildlife markets, urban parks and wastelands, zoos and even labs, where spillover from wildlife to humans may also occur. Furthermore, cities are transport hubs that form hotspots of import/export of living resources including animals, thus potentially promoting rapid and wide-scale spread of reservoir and vectors, hence pathogens, as well as pathogen admixture through viral recombination or bacterial plasmid exchanges. Finally, cities are deeply modified environments where living organisms, including reservoirs, vectors and pathogens, undergo strong selective pressures, thus opening the gate to evolutionary novelties, hence potential new infectious threats. As such, we believe urban socio-ecosystems should be paid more attention in terms of drivers of zoonotic emergence in humans needing adapted surveillance and mitigation. Accordingly, we propose and discuss several avenues of research and examples of actions that could be tested or generalized (e.g., focus on hotspots of emergence risks like informal settlements, wet markets or transport hubs; development of participative surveillance programs; shift towards inter-sectoral academic courses; massive investment into education and community information) in order to operationalize effective zoonotic surveillance. We advocate that this would allow ones to add emergence-preventive and early warning to usual outbreaks response strategies, thus significantly improving our collective ability to prevent zoonotic emergence and subsequent pandemics.

Trypanosoma lewisi belongs to the so-called atypical trypanosomes that occasionally affect humans. It shares the same hosts and flea vector of other medically relevant pathogenic agents as Yersinia pestis, the agent of plague. Increasing knowledge on the population structure (reproductive mode, population size, dispersal) of this parasite thus represents a challenging but important issue. The use of polymorphic genetic markers, together with suitable population genetics tools, is a convenient way to achieve such objectives. To date, the population biology of T. lewisi is poorly known and, to our knowledge, no population genetics studies have ever been conducted. Here, we present the development of nine microsatellite markers of this species. We investigated their polymorphism in different countries from Africa and South-East Asia from DNAs extracted from the spleen of their rodent reservoirs (essentially rat species). Several amplification problems arose, especially with South-East Asian individuals. This led to retain only those individuals with complete genotypes (most of them originating from West Africa, notably Cotonou, Benin) to ensure an optimal estimate of heterozygosity. Our results pointed towards a mainly (at least 95-99%) clonal mode of propagation, a strong subdivision at the smallest scale available (i.e., urban neighborhoods, i.e. 0.250 km²), and a generation time most probably shorter than 4 months. In future studies, more extensive sampling at smaller geographic scales (i.e., households), within a one- or two-months window and with improved amplification conditions, should lead to a more precise picture of the fine population structure of this parasite.

Simple Summary: The ultrastructural study of spermatozoa in parasites such as the Digenea provides data that, like classical morphological features, biological data, and genetic characterization, can help achieve a better understanding of phylogenetic relationships at different taxonomic levels. In this context, the present study provides the first ultrastructural data of spermatozoa in a digenean species of the genus Artyfechinostomum. These results increase the database of ultrastructural spermatological characteristics within the group of Echinostomatoidea. The comparison of these features with the existing data allows us to establish a coherent model of the sperm cell for species belonging to this superfamily. The study of sperm characteristics has proven useful for elucidating interrelationships in several groups of Platyhelminthes, such as digeneans. Thus, in the present work, the ultrastructural organization of the mature spermatozoon of the digenean Artyfechinostomum malayanum (Echinostomatidae), a parasite of Rattus norvegicus (Rodentia: Muridae) from Dong Thap Province, Vietnam, was investigated for the first time using transmission electron microscopy. The male gamete of A. malayanum exhibits two axonemes of different lengths, showing the 9 + '1' pattern of the Trepaxonemata, a nucleus, two mitochondria, two lateral expansions, two bundles of parallel cortical microtubules, external ornamentation, spine-like bodies, and granules of glycogen. Thus, the mature spermatozoon follows a Type V sperm model proposed for digeneans. We also highlight some noteworthy characteristics in Echinostomatidae with possible phylogenetic implications, such as two lateral expansions in the anterior region of the spermatozoon and two mitochondria. [ABSTRACT FROM AUTHOR]

Simple Summary: Heterakis spumosa Schneider, 1886 is a parasite commonly found in rodents, primarily associated with the black rat Rattus rattus and the brown rat R. norvegicus, two global invasive rodent species, and the house mouse Mus musculus. This parasite originated probably from Asia, and has been reported in various rodent species, but molecular information from its putative native region is still lacking. Our sampling efforts across Southeast Asia allowed us to collect and analyze this species from two localities in Lao PDR and five localities in Thailand. Additionally, specimens from Europe were included in the analysis. All specimens were analyzed using mtCOI gene and nuclear ribosomal ITS1. Our findings revealed the presence of two distinct clades of H. spumosa, with no discernible association with hosts and geographical localities. Heterakis spumosa, a parasitic worm infecting rodents, is globally prevalent in black rats, brown rats, and house mice. It is hypothesized to originate from Asia due to its widespread presence in Southeast Asia in various Murinae. Previous molecular studies focused on European, African, and Japanese specimens, but none included samples from the putative native range. Rodents were collected between 2008 and 2015 across various localities in Southeast Asia and Europe, identified by morphology or genetic barcoding. Viscera were examined or preserved for later inspection. DNA was extracted from H. spumosa. PCR amplification targeting the mtCOI gene and ITS1 region was conducted in this study using newly designed primers (based on Heterakis reference sequences). PCR amplicons were subsequently sequenced and analyzed. In this study, the phylogenetic analysis using ITS1 sequences revealed that Heterakis samples from Thai and Laotian rodents belong to the species H. spumosa, exhibiting low genetic variation compared to samples from other regions. Genetic distance calculations using mtCOI sequences confirmed the marked distinction of H. spumosa from other Heterakis species. Our phylogenetic analyses using partial mtCOI and ITS1 sequences have significantly enhanced our comprehension of the genetic diversity and evolutionary history of the nematode H. spumosa. [ABSTRACT FROM AUTHOR]