RESUMEN
Dengue fever is the most prevalent arboviral disease worldwide. Dengue virus (DENV), the etiological agent, is known to have been circulating in Senegal since 1970, though for a long time, virus epidemiology was restricted to the circulation of sylvatic DENV-2 in south-eastern Senegal (the Kedougou region). In 2009 a major shift was noticed with the first urban epidemic, which occurred in the Dakar region and was caused by DENV-3. Following the notification by Senegal, many other West African countries reported DENV-3 epidemics. Despite these notifications, there are scarce studies and data about the genetic diversity and molecular evolution of DENV-3 in West Africa. Using nanopore sequencing, phylogenetic, and phylogeographic approaches on historic strains and 36 newly sequenced strains, we studied the molecular evolution of DENV-3 in Senegal between 2009 and 2022. We then assessed the impact of the observed genetic diversity on the efficacy of preventive countermeasures and vaccination by mapping amino acid changes against vaccine strains. The results showed that the DENV-3 strains circulating in Senegal belong to genotype III, similarly to strains from other West African countries, while belonging to different clades. Phylogeographic analysis based on nearly complete genomes revealed three independent introduction events from Asia and Burkina Faso. Comparison of the amino acids in the CprM-E regions of genomes from the Senegalese strains against the vaccine strains revealed the presence of 22 substitutions (7 within the PrM and 15 within the E gene) when compared to CYD-3, while 23 changes were observed when compared to TV003 (6 within the PrM and 17 within the E gene). Within the E gene, most of the changes compared to the vaccine strains were located in the ED-III domain, which is known to be crucial in neutralizing antibody production. Altogether, these data give up-to-date insight into DENV-3 genomic evolution in Senegal which needs to be taken into account in future vaccination strategies. Additionally, they highlight the importance of the genomic epidemiology of emerging pathogens in Africa and call for the implementation of a pan-African network for genomic surveillance of dengue virus.
RESUMEN
Maize (Zea mays L) is one of main nutrients sources for humans and animals worldwide. In Africa, storage of maize ensures food resources availability throughout the year. However, it often suffers losses exceeding 20% due to insects such as the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera; Bostrichidae), major pest of stored maize in the tropical countries. This study aims to select resistant varieties to reduce maize storage losses and explain the physicochemical parameters role in grains susceptibility. In the first study, maize grains were artificially infested under no-choice method with insects. Susceptibility parameters such as weight loss, grain damage, number of emerged insects, median development time and susceptibility index varied significantly through maize varieties. Dobie susceptibility index (SI) was assessed as a major indicator of resistance. The most resistant varieties were Early-Thaï, DMR-ES and Tzee-Yellow. Conversely, Synth-9243, Obatampa and Synth-C varieties were susceptible. SWAN, Across-Pool and Tzee-White were classified as moderately resistant varieties. The insect reproductive potential was significantly different in the nine maize varieties and Early-Thaï, DMR-ES and Tzee-Yellow varieties were the least favourable host. To assess the relationship between grains physicochemical characteristics and varietal susceptibility, moisture, total phenolics, palmitic acid, proteins, amylose, density and grain hardness were evaluated according to standardized methods. Palmitic acid, SI, insects emerged and grain damage were significantly and positively correlated with each other, and negatively correlated with grains hardness, phenolics and amylose contents. Maize susceptibility index was significantly and negatively correlated to amylose, and phenolics contents and positively correlated to palmitic acid content. This study identified three resistant maize varieties to P. tuncatus and revealed that the major factors involved in this resistance were hardness, phenolic and amylose contents of grains.
