Yellow Fever Virus Maintained by Sabethes Mosquitoes during the Dry Season in Cerrado, a Semiarid Region of Brazil, in 2021

Abstract

In recent decades, waves of yellow fever virus (YFV) from the Amazon Rainforest have spread and caused outbreaks in other regions of Brazil, including the Cerrado, a savannah-like biome through which YFV usually moves before arriving at the Atlantic Forest. To identify the vectors involved in the maintenance of the virus in semiarid environments, an entomological survey was conducted after confirmation of yellow fever (YF) epizootics at the peak of the dry season in the Cerrado areas of the state of Minas Gerais. In total, 917 mosquitoes from 13 taxa were collected and tested for the presence of YFV. Interestingly, mosquitoes of the Sabethes genus represented 95% of the diurnal captured specimens, displaying a peak of biting activity never previously recorded, between 4:30 and 5:30 pm. Molecular analysis identified three YFV-positive pools, two from Sabethes chloropterus—from which near-complete genomes were generated—and one from Sa. albiprivus, whose low viral load prevented sequencing. Sa. chloropterus was considered the primary vector due to the high number of copies of YFV RNA and the high relative abundance detected. Its bionomic characteristics allow its survival in dry places and dry time periods. For the first time in Brazil, Sa. albiprivus was found to be naturally infected with YFV and may have played a role as a secondary vector. Despite its high relative abundance, fewer copies of viral RNA were found, as well as a lower Minimum Infection Rate (MIR). Genomic and phylogeographic analysis showed that the virus clustered in the sub-lineage YFVPA-MG, which circulated in Pará in 2017 and then spread into other regions of the country. The results reported here contribute to the understanding of the epidemiology and mechanisms of YFV dispersion and maintenance, especially in adverse weather conditions. The intense viral circulation, even outside the seasonal period, increases the importance of surveillance and YFV vaccination to protect human populations in affected areas.

Arbovirus surveillance in mosquitoes: Historical methods, emerging technologies, and challenges ahead

“…Identifying these species and understanding their behavior can significantly improve the entomological surveillance of arboviruses. 77 One of the main challenges in entomological surveillance is the proper conditioning, storage, and transport of mosquitoes after capture in the field. Collected samples must reach the laboratory under optimal conditions to facilitate taxonomic identification and reliable diagnoses.…”

Beyond Borders: Investigating the Mysteries of Cacipacoré, a Lesser-Studied Arbovirus in Brazil

“…Brazil is a hotspot for arboviral diseases, mainly due to its constellation of biodiverse ecotypes, which include: (a) the Amazon basin, encompassing the largest rainforest in the world [18][19][20][21][22], (b) the Atlantic forest, with the largest biodiversity and extending as far south and inland as Argentina and Paraguay [23][24][25][26][27], (c) the Pantanal, considered to be the largest wetland globally [6,[28][29][30][31][32][33][34], and (d) the Cerrado, a vast region of tropical savanna in eastern Brazil [35][36][37][38].…”