Zoonoses et urbanisation durable au Sud : comprendre les risques pour mieux les prévenir

Mise en contexte :L’empreinte anthropique croissante sur les habitats naturels est à l’origine de changements environnementaux significatifs qui impactent fortement la nature et l’évolution des relations entre hôtes et parasites (terme englobant ici les virus, bactéries, helminthes et protozoaires pouvant être pathogènes), avec notamment des contacts exacerbés entre humains et faune sauvage réservoir de ces parasites. Ces environnements perturbés sont propices à la circulation de zoonoses (maladies infectieuses se transmettant entre l’animal et l’humain), particulièrement dans les régions du Sud confrontées aux défis multisectoriels imposés par les mutations anthropiques actuelles. L’urbanisation intensive représente une situation emblématique de ce contexte où l’humain est à la fois acteur et victime de ces perturbations environnementales. Prévenir et gérer de manière efficace et durable les risques zoonotiques dans ces régions à forte croissance urbaine est donc une priorité majeure de développement durable.À retenir :Une des clés essentielles pour répondre aux enjeux des villes durables est de parvenir à endiguer les risques sanitaires zoonotiques liés à l’urbanisation intensive en cours dans les régions du Sud. Dans ce contexte, l’approche Eco Health apparaît fondamentale pour appréhender de manière holistique les mécanismes et processus multifactoriels à l’œuvre dans les relations zoonoses/urbanisation. Essentiellement basée sur une recherche partenariale avec les acteurs locaux, depuis la coconstruction des projets jusqu’à l’implémentation contextualisée des solutions, cette approche intégrée de la santé (entre science interdisciplinaire, décisions politiques et actions communautaires) permet l’identification des leviers d’actions les plus pertinents pour une surveillance intégrée des zoonoses

Rodents as Hosts of Pathogens and Related Zoonotic Disease Risk

International audienceRodents are known to be reservoir hosts for at least 60 zoonotic diseases and are known to play an important role in their transmission and spread in different ways. We sampled different rodent communities within and around human settlements in Northern Senegal, an area subjected to major environmental transformations associated with global changes. Herein, we conducted an epidemiological study on their bacterial communities. One hundred and seventy-one (171) invasive and native rodents were captured, 50 from outdoor trapping sites and 121 rodents from indoor habitats, consisting of five species. The DNA of thirteen pathogens was successfully screened on the rodents' spleens. We found: 2.3% of spleens positive to Piroplasmida and amplified one which gave a potentially new species Candidatus "Theileria senegalensis"; 9.35% of Bartonella spp. and amplified 10, giving three genotypes; 3.5% of filariasis species; 18.12% of Anaplasmataceae species and amplified only 5, giving a new potential species Candidatus "Ehrlichia senegalensis"; 2.33% of Hepatozoon spp.; 3.5% of Kinetoplastidae spp.; and 15.2% of Borrelia spp. and amplified 8 belonging all to Borrelia crocidurae. Some of the species of pathogens carried by the rodents of our studied area may be unknown because most of those we have identified are new species. In one bacterial taxon, Anaplasma, a positive correlation between host body mass and infection was found. Overall, male and invasive rodents appeared less infected than female and native ones, respectively

Pterygodermatites (Mesopectines) niameyensis n. sp. (Nematoda: Rictulariidae), a parasite of Mastomys natalensis (Smith, 1834) (Rodentia: Muridae) from Niger.

International audiencePterygodermatites (Mesopectines) niameyensis n. sp. is described from Mastomys natalensis in Niamey/Niger (West Africa). It differs from other species of same subgenus by the morphology of the head, which presents 4 simple cephalic papillae and nearly axial oral opening, a number of caudal papillae, precloacal cuticular formations, and the spicule length/body length ratio. Scanning electron microscopy shows the presence of 2 pairs of lateral sensory structures for male worms

Whipworm diversity in West African rodents: a molecular approach and the description of Trichuris duplantieri n. sp (Nematoda: Trichuridae)

Whipworms were collected from rodents (Muridae) from six West African countries: Burkina-Faso, the Islamic Republic of Mauritania, and the Republics of Benin, Guinea, Mali and Senegal. Molecular sequences (ITS-1, 5.8S and ITS-2 of the ribosomal DNA gene) and morphometric characters were analysed in Trichuris (Nematoda: Trichuridae) specimens found in seven host species: Arvicanthis niloticus, Gerbilliscus gambianus, Gerbillus gerbillus, G. tarabuli, Mastomys erythroleucus, M. huberti and M. natalensis. Phylogenetic analyses revealed three clades, one recognised as Trichuris mastomysi, previously recorded in M. natalensis from Tanzania, and the other two previously undescribed. A new species named Trichuris duplantieri n. sp., found in Gerbillus spp. from Mauritania, was characterised using molecular and morphometric methods

Rodents and bacterial communities: from host-parasite interactions to sanitary concerns

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Association between temporal patterns in helminth assemblages and successful range expansion of exotic Mus musculus domesticus in Senegal

International audienceRelationships between parasitism and invasion success are increasingly evidenced in the literature. However, the dynamic nature of the major parasite-related processes has been rarely taken into account until now, while the residence time of invaders in colonized regions was shown to be associated to crucial changes in parasite communities. Here, we strive to bridge this gap using a temporal survey of rodent populations along one invasion route of the exotic house mouseMus musculus domesticusthat currently invades North Senegal. In this study, we investigated whether gastrointestinal helminth (GIH) assemblages changed over time in native (Mastomys erythroleucus) and/or invasive (M. m. domesticus) rodent populations sampled at an invasion front, and whether these potential changes may be associated to the invasion success of the exotic mouse. Four years separated two rodent sampling campaigns (2013 and 2016/17) in six localities. Despite being relatively short, the timeframe considered here allowed to evidence significant patterns in rodent communities and their GIH assemblages. At the host community level, we showed that the exotic mouse was now established at all sites, becoming the dominant species in sites where it was not recorded before. At the GIH community level, increased infection of the single shared cestode (Mathevotaenia symmetrica) in both rodent species brought support to the "spill-back" hypothesis. Infection levels of GIH that remained low at the invasion front in invading mice over time also supported the "enemy release" hypothesis. Both hypotheses should deserve further experimental work to demonstrate their role in the invasion success of the house mouse in Senegal

Differential immune gene expression associated with contemporary range expansion of two invasive rodents in Senegal

International audienceBiological invasions are major anthropogenic changes associated with threats to biodiversity and health. However, what determines the successful establishment and spread of introduced populations remains unclear. Here, we explore several hypotheses linking invasion success and immune phenotype traits, including those based on the evolution of increased competitive ability concept. We compared gene expression profiles between anciently and recently established populations of two major invading species, the house mouse Mus musculus domesticus and the black rat Rattus rattus, in Senegal (West Africa). Transcriptome analyses identified differential expression between anciently and recently established populations for 364 mouse genes and 83 rat genes. All immune-related genes displaying differential expression along the mouse invasion route were overexpressed at three of the four recently invaded sites studied. Complement activation pathway genes were overrepresented among these genes. By contrast, no particular immunological process was found to be overrepresented among the differentially expressed genes of black rat. Changes in transcriptome profiles were thus observed along invasion routes, but with different specific patterns between the two invasive species. These changes may be driven by increases in infection risks at sites recently invaded by the house mouse, and by stochastic events associated with colonization history for the black rat. These results constitute a first step toward the identification of immune eco-evolutionary processes potentially involved in the invasion success of these two rodent species