Amplification of the sylvatic cycle of dengue virus type 2, Senegal, 1999-2000: entomologic findings and epidemiologic considerations.
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 mosquitoes captured in the forest gallery and surrounding villages. Isolates were obtained from previously described vectors, Aedes furcifer, Ae. taylori, Ae. luteocephalus, and--for the first time in Senegal--from Ae. aegypti and Ae. vittatus. A retrospective analysis of sylvatic DENV-2 outbreaks in Senegal during the last 28 years of entomologic investigations shows that amplifications are periodic, with intervening, silent intervals of 5-8 years. No correlation was found between sylvatic DENV-2 emergence and rainfall amount. For sylvatic DENV-2 vectors, rainfall seems to particularly affect virus amplification that occurs at the end of the rainy season, from October to November. Data obtained from investigation of preimaginal (i.e., nonadult) mosquitoes suggest a secondary transmission cycle involving mosquitoes other than those identified previously as vectors.
Diallo
Mawlouth
M
Institut Pasteur de Dakar, Dakar, Senegal. diallo@pasteur.sn
Ba
Yamar
Y
Sall
Amadou A
AA
Diop
Ousmane M
OM
Ndione
Jacques A
JA
Mondo
Mireille
M
Girault
Lang
L
Mathiot
Christian
C
D000330:Aedes / Q000821:virology*; D000818:Animals; D003716:Dengue Virus / Q000302:isolation & purification* / Q000472:pathogenicity; D005260:Female; D008297:Male; D011891:Rain; D012675:Senegal