Vertical transmission of dengue virus in Aedes aegypti and its role in the epidemiological persistence of dengue in Central and Southern Mexico.

Abstract

Aedes aegypti and Aedes albopictus are the main mosquito species responsible for dengue virus (DENV) transmission to humans in the tropical and subtropical regions of the world. The role of vertical transmission in the epidemiology of dengue and the maintenance of this arbovirus in nature during interepidemic periods remain poorly understood, and DENV vertical transmission could sustain the existence of virus reservoirs within Aedes populations. Between April 2011 and October 2012, we monitored vertical transmission of DENV in Ae. aegypti and Ae. albopictus in 9 cities of 4 Mexican states. Aedes eggs were collected in ovitraps, then adults were reared under laboratory conditions and their heads were used to infect C6/36 cells. The presence of flavivirus was detected by immunofluorescence assays (IFA), and DENV infection was confirmed by RT-PCR. About 96% of reared adults were Ae. aegypti and 4.0% were Ae. albopictus. No infection was detected in Ae. albopictus, whereas 54 of 713 (7.8%) of Ae. aegypti pools tested positive. A minimum infection rate (MIR) of 2.52 per 1000mosquitoes was estimated for Ae. aegypti. DENV-1, DENV-2 & DENV-3 serotypes were detected even during interepidemic periods. This study reports the evidence of vertical transmission of dengue virus with viral isolation and molecular confirmation in Ae. aegypti eggs collected in four endemic regions of Central and Southern Mexico. Vertical transmission may play a role as a reservoir mechanism during mosquito dormancy in interepidemic periods but with minor participation in transmission during epidemic periods.