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Rift Valley fever (RVF) is one of the major viral arthropod-borne diseases in Africa. In recent decades, RVF virus (RVFV), the causative agent of RVF, has been responsible for multiple outbreaks in West Africa with important consequences on human and animal health. In particular, an outbreak occurred in 2010 after heavy rains in the desertic region of Adrar, Mauritania. It was characterized by the appearance of severe clinical signs among dromedary camels. Another one occurred in 2013-2014 across Senegal and the southern part of Mauritania. In this study, we characterized two RVFV field strains isolated during these two outbreaks. The first strain, MRU25010-30, was isolated from a camel (2010) while the second, MRU2687-3, was isolated from a goat (2013). By deep-sequencing and rapid amplification of cDNA-ends by polymerase chain reaction, we successfully sequenced the complete genome of these two RVFV strains as well as the reference laboratory strain ZH548. Phylogenetic analysis showed that the two field viruses belong to two different RVFV genetic lineages. Moreover, we showed that MRU25010-30 replicates more efficiently in various in vitro cell culture models than MRU2687-3 and ZH548. In vivo, MRU25010-30 caused rapid death of BALB/c mice and proved to be more virulent than MRU2687-3, regardless of the route of inoculation (subcutaneous or intranasal). The virulence of MRU25010-30 is associated with a high viral load in the liver and serum of infected mice, while the death of mice infected with MRU2687-3 and ZH548 correlated with a high viral load in the brain. Altogether, the data presented in this study provide new avenues to unveil the molecular viral determinants that modulate RVFV virulence and replication capacity., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Chabert et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Global eradication of peste des petits ruminants (PPR) is planned for 2030 by international animal health organizations in collaboration with national partners. As the deadline approaches, it is fundamental that the PPR status in each country is determined. In addition, the identification of other pathogens of small ruminants that share common geographical locations and can produce similar clinical signs is also important for differential diagnosis. With this in mind, 37 samples collected from goats and sheep presenting respiratory symptoms in Mauritania in 2023 were screened for the presence of PPR virus, Capripoxvirus, Pasteurella multocida and Mycoplasma capricolum subspecies capripneumoniae (Mccp) using a one-step multiplex RT-qPCR assay. None of the samples were positive for Capripoxvirus or P. multocida. Nine of them were positive for PPRV and sequence analysis of a segment of the PPRV nucleoprotein revealed that they belonged to lineage IV and were similar to viruses recently identified in Côte D'Ivoire, Guinea, and Niger indicating transboundary movement. The full genome of one representative virus was also generated. Mccp was identified in eight samples and multi-locus sequence analysis (MLSA) identified them as belonging to MLSA Group 3 together with Mccps identified in China, Tajikistan, Turkey and the United Arab Emirates. This is the first time that such a study has been undertaken in Mauritania and the data generated should be of interest to those involved in the management of goat diseases in Mauritania and neighbouring countries., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)