Detection of dengue viruses in field-caught Aedes aegypti (Diptera: Culicidae) in Maracay, Aragua state, Venezuela by type-specific polymerase chain reaction.

Abstract Virological surveillance of dengue viruses in Aedes aegypti populations constitutes a powerful tool for early prediction of dengue outbreaks. We have standardized a protocol for viral RNA extraction from individual and pools of mosquitoes that permits a sensitive detection of dengue virus without RNA degradation or PCR inhibition when we apply a semi-nested RT-PCR. The limit of detection for each dengue serotype was 0.1 PFU. In a prospective field study conducted from November 2000 to December 2001, adult female A . aegypti mosquitoes from several municipalities with high dengue transmission in Maracay, Aragua State, Venezuela were collected and screened for dengue viruses using RT-PCR. We analyzed a total of 296 A . aegypti pools (1,632 mosquitoes); of these, 154 pools (469 mosquitoes) were collected from houses with persons with clinical diagnosis of dengue ( dengue houses) , and 142 pools (1,163 mosquitoes) from adjacent residences ( neighbour houses ). From the dengue houses , eight mosquito pools (5.2%) were positive for DENV-1 (0.7%), DENV-3 (3.2%) and DENV-4 (1.3%) viruses. From the neighbour houses, 18 mosquito pools (12.7%) were positive for DENV-3 (12%) and DENV-4 (0.7%) viruses. From these 26 RT-PCR positive mosquito pools (containing 1–25 mosquitoes each), 22 pools (84.6%) were positive for DENV-3. The most prevalent serotype in the 2001 dengue outbreak was also DENV-3. The minimum infection rate in both A . aegypti collections, from dengue houses and neighbour houses was 17 and 15 per 1,000, respectively. The relevance of these results for dengue surveillance is discussed.