Potential for sylvatic and urban Aedes mosquitoes from Senegal to transmit the new emerging dengue serotypes 1, 3 and 4 in West Africa

Abstract

Dengue fever (DEN) is the most common arboviral disease in the world and dengue virus (DENV) causes 390 million annual infections around the world, of which 240 million are inapparent and 96 million are symptomatic. During the past decade a changing epidemiological pattern has been observed in Africa, with DEN outbreaks reported in all regions. In Senegal, all DENV serotypes have been reported. These important changes in the epidemiological profile of DEN are occurring in a context where there is no qualified vaccine against DEN. Further there is significant gap of knowledge on the vector bionomics and transmission dynamics in the African region to effectively prevent and control epidemics. Except for DENV-2, few studies have been performed with serotypes 1, 3, and 4, so this study was undertaken to fill out this gap. We assessed the vector competence of Aedes (Diceromyia) furcifer, Ae. (Diceromyia) taylori, Ae. (Stegomyia) luteocephalus, sylvatic and urban Ae. (Stegomyia) aegypti populations from Senegal for DENV-1, DENV-3 and DENV-4 using experimental oral infection. Whole bodies and wings/legs were tested for DENV presence by cell culture assays and saliva samples were tested by real time RT-PCR to estimate infection, disseminated infection and transmission rates. Our results revealed a low capacity of sylvatic and urban Aedes mosquitoes from Senegal to transmit DENV-1, DENV-3 and DENV-4 and an impact of infection on their mortality. The highest potential transmission rate was 20% despite the high susceptibility and disseminated infection rates up to 93.7% for the 3 Ae. aegypti populations tested, and 84.6% for the sylvatic vectors Ae. furcifer, Ae. taylori and Ae. luteocephalus.

Author summary

Dengue fever remains a major public health problem in all tropical regions of the world and causes 390 million infections each year. In Africa, while dengue outbreaks were rare during the last century, recurrent urban epidemic have been reported in all regions the last decade. Serotype 3, never reported in West Africa, caused major outbreaks in 2009 in several capital cities while serotype 2, usually confined to the forest cycle, spilled over into urban areas in Senegal and Mauritania in 2014–2015. These changes are occurring in a context where vector control remains the only effective approach to prevent and control epidemics. However, the design and the implementation of efficient vector control require an accurate knowledge of the vector bionomics and competence while such data are lacking in the African region. To fill out this gap we experimentally infected domestic and wild mosquitoes from Senegal to assess their vector competence for dengue serotypes 1, 3 and 4. Finally both domestic and wild Senegalese mosquitoes showed a low ability to transmit dengue viruses.