Dengue is an arthropod-borne viral disease of major public health importance worldwide. Currently, the dengue pandemic affects more than 100 countries, including nations in Africa, the Americas, the Indian subcontinent, Southeast Asia, the Eastern Mediterranean, and the Western Pacific [1]. The World Health Organization (WHO) estimates there are 50 million annual cases of dengue infection worldwide, about 500,000 hospital admissions, and 22,000 dengue-related deaths. Globally, more than 2.5 billion people are at risk for this disease. The emergence of dengue in the Americas has been especially dramatic [2,3].
Dengue virus (DENV) is comprised of four closely related, but antigenically distinct serotypes (DENV-1, DENV-2, DENV-3 and DENV-4), multiple genotypes enclosed in each serotype [4]. The Aedes aegypti mosquito is the primary vector for all four serotypes. The mosquitoes become infected after feeding on a viremic individual, then a reported EIP of 7–14 days is required before the mosquitoes can transmit the virus to a new host [2,5]. Environmental factors (including temperature and humidity) as well as intrinsic factors (such as vector competence and viral genotype) affect the EIP [6].
Host organ and cell susceptibility and permissiveness condition virus tropisms in an organism [7]. A number of studies have investigated DENV-vector interactions [8-14], and the important role of virus genotype in efficient Aedes aegypti infection has been revealed [15]. In this study, we wanted to determine the virogenesis of DENV-2 infection in recently colonized vector mosquitoes from a dengue endemic area, which previously had been shown to be very susceptible to DENV infection [16].
In the natural course of infection for the virus, DENV is ingested in a blood meal, then it encounters and must overcome midgut infection and escape barriers [17], which vary among mosquito populations. Infection of mosquito midguts is known to occur in a dose-dependent manner [16]. Elucidation of the kinetics of replication and tropism of virus in recently colonized (field relevant) Aedes aegypti mosquitoes would provide a better understanding of transmission potential and vector-virus interactions that condition dengue epidemiology and epidemic potential. In this study, we determined: 1) the kinetics of DENV infection in orally infected mosquitoes, 2) the DENV-2 tropisms for different mosquito tissues and organs, 3) a possible anatomic explanation for virus dissemination from the midgut, and 4) the minimal time required for infection of salivary glands in recently colonized Aedes aegypti mosquitoes from Chetumal, Mexico and in a long colonized or a selected Aedes aegypti strain.
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