Amplification of the Sylvatic Cycle of Dengue Virus Type 2, Senegal, 1999–2000: Entomologic Findings and Epidemiologic Considerations

摘要

After 8 years of silence, dengue virus serotype 2 (DENV-2)reemerged in southeastern Senegal in 1999. Sixty-four DENV-2 strains were isolated in 1999 and 9 strains in 2000 from mos-quitoes captured in the forest gallery and surrounding villages.Isolates were obtained from previously described vectors,Aedes furcifer, Ae. taylori, Ae. luteocephalus, and—for the firsttime in Senegal—from Ae. aegypti and Ae. vittatus. A retrospec-tive analysis of sylvatic DENV-2 outbreaks in Senegal duringthe last 28 years of entomologic investigations shows thatamplifications are periodic, with intervening, silent intervals of5–8 years. No correlation was found between sylvatic DENV-2emergence and rainfall amount. For sylvatic DENV-2 vectors,rainfall seems to particularly affect virus amplification thatoccurs at the end of the rainy season, from October toNovember. Data obtained from investigation of preimaginal (i.e.,nonadult) mosquitoes suggest a secondary transmission cycleinvolving mosquitoes other than those identified previously asvectors