Potential Role of Sylvatic and Domestic African Mosquito Species in Dengue Emergence

Abstract

Dengue virus 2 (DENV-2) strains that circulate in sylvatic habitats of Senegal and other parts of west Africa are believed to represent ancestral forms that evolved into endemic/epidemic strains that now circulate widely in urban areas of the tropics. Previous studies suggested that the evolution of the endemic/epidemic strains was mediated by adaptation to the peridomestic mosquito vectors Aedes aegypti and Ae. albopictus. We conducted experimental infections using sylvatic and peridomestic Senegalese mosquitoes, and both sylvatic and urban DENV-2 strains to determine if endemic DENV-2 adaptation was vector species specific, and to assess ancestral vector susceptibility. Aedes furcifer and Ae. luteocephalus, probable sylvatic vectors, were highly susceptible to both sylvatic and urban DENV-2 strains. In contrast, sylvatic Ae. vittatus and both sylvatic and peridomestic populations of Ae. aegypti were relative refractory to all DENV-2 strains tested. These results indicate that adaptation of DENV-2 to urban vectors did not result in a loss of infectivity for some African sylvatic vectors. Implications for dengue emergence in west Africa are discussed.

Impact of Climate and Mosquito Vector Abundance on Sylvatic Arbovirus Circulation Dynamics in Senegal

“…22 The DENV dissemination rates for Ae. furcifer captured in Senegal can be as high as 75%, 13 whereas those for YFV are estimated at 20%. 23 These estimates, based on experimental infections, were highly variable and depended on specific virus strain and mosquito genetics.…”

“…Collection methods have been described previously. 2,3,13 Briefly, mosquitoes were collected at savanna and gallery forest sites surrounding Kedougou (12 11 W, 12 33 N) (Figure 2). The majority of mosquitoes were collected by human landing collection during the rainy season (generally June through October), with individuals collecting mosquitoes for 2 hours around dusk.…”

Abbreviations and acronyms

“…In studies directly comparing collections within Senegal, wide variation in VC was shown for both high-passage (Sylla et al, 2009) and low-passage field isolates of DENV-2 (Diallo et al, 2005(Diallo et al, , 2008. Especially, sylvatic collections from south-eastern Senegal were more refractory than other collections from throughout the country.…”

“…aegypti with a viral isolate collected in proximity seems to be the most informative approach (Lambrechts et al, 2009). Diallo et al (2005Diallo et al ( , 2008 followed this process by examining the VC of Ae. aegypti from Senegal with multiple local isolates of DENV-2.…”

“…aegypti from West Africa have shown that mosquitoes are more refractory for both DENV (Tabachnick et al, 1985;Bosio and Beaty, 1998) and yellow fever virus (YFV) (Tabachnick et al, 1985;Miller and Mitchell, 1991) compared to Ae. aegypti collected from the Americas or Asia (Diallo et al, 2005(Diallo et al, , 2008.…”