Effet du chlorure de sodium sur la germination de graines de Ricinus communis L.

Ricinus communis L (ricin) figure parmi les espèces du Programme biocarburant au  Sénégal. Sa culture sur des terrains incultes (terres salées) constitue une alternative pour éviter une concurrence sur les terres à vocation agricole. C’est pourquoi le taux de germination (TG) de sept accessions de graines de ricin a été étudié pendant 15 jours sous des concentrations croissantes de NaCl (0; 20; 50; 80; 100; 150 et 200 mM). Les résultats ont montré une large variabilité de tolérance au sel au stade de la germination. Les accessions 3 et 8 ont été très sensibles avec des TG réduits seulement à la concentration 20 mM NaCl. Les accessions 1, 6 et 7 n’ont pas toléré la concentration 50 mM. L’accession 5 n’a toléré que les teneurs < 80 mM. L’accession 4 a germé dans les milieux ≤ 100 mM NaCl. Elle n’a manifesté une perte significative de TG qu’en présence de 150 mM NaCl. Elle a été la moins affectée par l’effet ralentisseur du sel sur la vitesse de germination. Ces résultats permettent de dire que le mode d’action de NaCl sur la germination est de nature osmotique et/ou toxique.Mots clés : Ricin, espèce, biocarburant, tolérance au sel, teneur en sel, Sénégal

Spillover, hybridization, and persistence in schistosome transmission dynamics at the human-animal interface.

Zoonotic spillover and hybridization of parasites are major emerging public and veterinary health concerns at the interface of infectious disease biology, evolution, and control. Schistosomiasis is a neglected tropical disease of global importance caused by parasites of the Schistosoma genus, and the Schistosoma spp. system within Africa represents a key example of a system where spillover of animal parasites into human populations has enabled formation of hybrids. Combining model-based approaches and analyses of parasitological, molecular, and epidemiological data from northern Senegal, a region with a high prevalence of schistosome hybrids, we aimed to unravel the transmission dynamics of this complex multihost, multiparasite system. Using Bayesian methods and by estimating the basic reproduction number (R0 ), we evaluate the frequency of zoonotic spillover of Schistosoma bovis from livestock and the potential for onward transmission of hybrid S. bovis × S. haematobium offspring within human populations. We estimate R0 of hybrid schistosomes to be greater than the critical threshold of one (1.76; 95% CI 1.59 to 1.99), demonstrating the potential for hybridization to facilitate spread and establishment of schistosomiasis beyond its original geographical boundaries. We estimate R0 for S. bovis to be greater than one in cattle (1.43; 95% CI 1.24 to 1.85) but not in other ruminants, confirming cattle as the primary zoonotic reservoir. Through longitudinal simulations, we also show that where S. bovis and S. haematobium are coendemic (in livestock and humans respectively), the relative importance of zoonotic transmission is predicted to increase as the disease in humans nears elimination

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Chapter 9. The Fish Monitoring Programme of the Onchocerciasis Control Programme in West Africa: a Model for Fish and Fisheries Preservation in the Face of Development

9.1 Introduction Human onchocerciasis, or river blindness, is a filarial disease caused by Onchocerca volvulus which, in West Africa, is transmitted by the adult female of the blackfly, Simulium damnosum s.l. (Zimmerman et al, 1992). It was common mainly along the fertile valleys of the watercourses and was not only a major public health problem but also an obstacle to the socioeconomic development of the infested areas. In 1974, the concern of the governments of seven of the most affected co..