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International audience; Bartonellae are bacteria associated with mammals and their ectoparasites. Rodents often host different species of Bartonella. The aim of this study was to investigate the presence of Bartonella spp. in African giant pouched rats (Cricetomys gambianus) and their ectoparasites in Dakar, Senegal. In 2012, 20 rats were caught, and their fleas were identified. DNA was extracted from 170 selected fleas and qPCR was carried out to detect Bartonella spp. Subsequently, a Bartonella culture was performed from the rat blood samples and the isolated strains (16S rRNA, rpoB, ftsZ and ITS3) were genotyped. A total of 1117 fleas were collected from 19 rats and identified as Xenopsylla cheopis, the tropical rat flea. Bartonella DNA was detected in 148 of 170 selected fleas (87.1%). In addition, Bartonella strains were isolated from the blood of 17 rats (85%). According to Bartonella gene-sequence-based criteria for species definition, the isolated strains were identified as B. massiliensis (four strains) and two potential new species related to the zoonotic B. elizabethae. In this paper, these potentially new species are provisionally called Candidatus Bartonella militaris (11 strains) and Candidatus Bartonella affinis (two strains) until their description has been completed. Cricetomys gambianus and its fleas could constitute a public health risk in Dakar due to the high prevalence of Bartonella infection reported.

Mosquito transmission of dengue viruses to humans starts with infection of skin resident cells at the biting site. There is great interest in identifying transmission-enhancing factors in mosquito saliva in order to counteract them. Here we report the discovery of high levels of the anti-immune subgenomic flaviviral RNA (sfRNA) in dengue virus 2-infected mosquito saliva. We established that sfRNA is present in saliva using three different methods: northern blot, RT-qPCR and RNA sequencing. We next show that salivary sfRNA is protected in detergent-sensitive compartments, likely extracellular vesicles. In support of this hypothesis, we visualized viral RNAs in vesicles in mosquito saliva and noted a marked enrichment of signal from 3'UTR sequences, which is consistent with the presence of sfRNA. Furthermore, we show that incubation with mosquito saliva containing higher sfRNA levels results in higher virus infectivity in a human hepatoma cell line and human primary dermal fibroblasts. Transfection of 3'UTR RNA prior to DENV2 infection inhibited type I and III interferon induction and signaling, and enhanced viral replication. Therefore, we posit that sfRNA present in salivary extracellular vesicles is delivered to cells at the biting site to inhibit innate immunity and enhance dengue virus transmission. Support for this research came from a fellowship from the McLauglin Family Foundation to TS, scholarships from the Fondation pour la Recherche Médicale (FRM project SPF202110013925) to HM, from the Institut Méditerranéen Hospitalier (IHU, Marseille) to IMSP and from the graduate school French Ministry of Higher Education and Research to FRC and FR, UTMB start-up funds and Cancer Prevention & Research Institute of Texas grant RP200650 to LJK and MKS, the Ministerio de Ciencia e Innovación (PID2020-115696RB-I00) to MAM-R, Cancer Prevention & Research Institute of Texas grant ID RR210018 to GN, Ministry of Education (Singapore) Tier3 grant (MOE2015-T3-1-003) to RMK and JP, a National Medical Research Council (Singapore) ZRRF grant (ZRRF/007/2017) to JP, a French Agence Nationale de la Recherche grant (ANR-20-CE15-0006) to JP, and the Duke-NUS Signature Research Programme funded by the Agency for Science Technology and Research (A*Star Singapore) and NIH/NIAID P01 AI150585 to MAGB. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

International audience; The close phylogenetic relationship between humans and other primates creates exceptionally high potential for pathogen exchange. The surveillance of pathogens in primates plays an important role in anticipating possible outbreaks. In this study, we conducted a molecular investigation of pathogenic bacteria in feces from African nonhuman primates (NHPs). We also investigated the pathogens shared by the human population and gorillas living in the same territory in the Republic of Congo. In total, 93% of NHPs (n=176) and 95% (n=38) of humans were found to carry at least one bacterium. Non-pallidum Treponema spp. (including T. succinifaciens, T. berlinense, and several potential new species) were recovered from stools of 70% of great apes, 88% of monkeys, and 79% of humans. Non-tuberculosis Mycobacterium spp. were also common in almost all NHP species as well as in humans. In addition, Acinetobacter spp., members of the primate gut microbiota, were mainly prevalent in human and gorilla. Pathogenic Leptospira spp. were highly present in humans (82%) and gorillas (66%) stool samples in Congo, but were absent in the other NHPs, therefore suggesting a possible gorillas-humans exchange. Particular attention will be necessary for enteropathogenic bacteria detected in humans such as Helicobacter pylori, Salmonella spp. (including S. typhi/paratyphi), Staphyloccocus aureus, and Tropheryma whipplei, some of which were also present in gorillas in the same territory (S. aureus and T. whipplei). This study enhances our knowledge of pathogenic bacteria that threaten African NHPs and humans by using a non-invasive sampling technique. Contact between humans and NHPs results in an exchange of pathogens. Ongoing surveillance, prevention, and treatment strategies alone will limit the spread of these infectious agents.

Background Species of the Tabanidae are potent vectors of human and animal diseases, but they have not been thoroughly investigated to date. In Senegal (West Africa), little information is available on these dipterans. Our objective in this study was to investigate Senegalese tabanids and their diversity by using molecular and proteomics approaches, as well as their associated pathogens. Methods A total of 171 female tabanids were collected, including 143 from Casamance and 28 from Niokolo-Koba. The samples were identified morphologically by PCR sequencing and by MALDI-TOF MS, and PCR analysis was employed for pathogen detection and blood-meal characterization. Results The morphological identification revealed four species concordantly with the molecular identification: Atylotus fuscipes (79.5%), Tabanus guineensis (16.4%), Chrysops distinctipennis (3.5%) and Tabanus taeniola (0.6%) (not identified by PCR). The molecular investigation of pathogens revealed the presence of Trypanosoma theileri (6.6%), Leishmania donovani (6.6%), Setaria digitata (1.5%), Rickettsia spp. (5.1%) and Anaplasmataceae bacteria (0.7%) in A. fuscipes. Tabanus guineensis was positive for L. donovani (35.7%), S. digitata (3.6%) and Anaplasmataceae (17.8%). Leishmania donovani has been detected in 50% of C. distinctipennis specimens and the only T. taeniola specimen. No Piroplasmida, Mansonella spp. or Coxeilla burnetii DNA was detected. In addition to humans (96.43%), Chlorocebus sabeus, a non-human primate, has been identified as a host of (3.57%) analysed tabanids. MALDI-TOF MS enabled us to correctly identify all tabanid species that had good quality spectra and to create a database for future identification. Conclusions Tabanids in Senegal could be vectors of several pathogens threatening animal and public health. To fully characterize these dipterans, it is therefore necessary that researchers in entomology and infectiology employ molecular characterization and mass spectrometric techniques such as MALDI-TOF MS to analyse these dipterans in Senegal and West Africa.