Evaluation of Mosquito Densoviruses for Controlling Aedes aegypti (Diptera: Culicidae): Variation in Efficiency due to Virus Strain and Geographic Origin of Mosquitoes

Abstract

Four mosquito densovirus strains were assayed for mortality and infectivity against Aedes aegypti larvae from different geographic regions. The viral titers were quantified by real-time PCR using TaqMan technology. Firstinstar larvae were exposed to the same titer of each densovirus strain for 48 hours. All strains of densoviruses exhibited larvicidal activity and caused more than 80% mortality and infectivity in the three mosquito strains. AalDNV-exposed larvae had the highest mortality rate. The mean time to death of AalDNV-exposed larvae was shorter than other DNVs-exposed larvae. We can conclude that different densovirus strains exhibit some variations in their pathogenicity to different populations of Ae. aegypti mosquitoes. A few mosquitoes from Chachoengsao and Bangkok exposed to AeDNV and AThDNV survived to the adult stage to lay eggs and showed 22% to 50% vertical transmission in the F1 generation. Phylogenetic analysis of four densovirus strains indicated that mosquito densoviruses are separated into two distinct clades.

Discovery of DNA Viruses in Wild-Caught Mosquitoes Using Small RNA High throughput Sequencing

“…Mosquitoes are the most important vector of WNV, DENV, CHIKV and YFV, and controlling mosquito populations is an important way of preventing epidemics of these life-threatening diseases. Among the many approaches to mosquito control [27], environmentally friendly densoviruses have been considered as a biological control agents [20,26,27,28]. Field trials using a densovirus that infects A. aegypti mosquitoes showed that the virus had significant efficiency, although most densoviruses take 2-20 days to kill their insect hosts [29], making this agent unsuitable for commercial use.…”

Biological Control of Mosquito Vectors: Past, Present, and Future

“…Laboratory studies using MDVs have shown high rates (>80%) of Ae. aegypti larval mortality [128]. However, the efficacy and sustainability of MDVs as a biocontrol agent was tested in and among oviposition sites in large laboratory cages, but was not shown to significantly reduce Ae.…”

Induction of apoptosis in densovirus infected Aedes aegypti mosquitoes

“…While densoviruses are known to be highly pathogeneic towards Aedes mosquito larvae (Barreau et al, 1996;Hirunkanokpun et al, 2008;Jousset et al, 1993), studies have suggested that repeated challenge of successive generations of mosquitoes surviving prior densovirus challenge results in significantly reduced mortality (Roekring et al, 2006). Therefore, understanding both the mechanism of mortality in densovirus infected mosquitoes, as well as the basis for decreased susceptibility to successive generation challenge are important for developing denosoviruses as anti-mosquito biological control agents.…”

“…To date several mosquito densoviruses have been characterized, including the Aedes densovirus designated AeDNV isolated from an A. aegypti mosquito colony (Lebedeva et al, 1973), an A. albopictus densonucleosis virus designated AalDNV, isolated from a persistently infected subclone of C6/36 cells (Jousset et al, 1993) and a densovirus isolated from adult A. albopictus mosquitoes in Thailand designated AThDNV (Kittayapong et al, 1999). AeDNV, AalDNV and AThDNV have all been shown to be highly pathogenic against A. aegypti larvae (Barreau et al, 1996;Hirunkanokpun et al, 2008;Jousset et al, 1993). However, experiments have shown that challenge of successive generations of A. aegypti with AThDNV results in an increasing proportion of surviving mosquitoes (Roekring et al, 2006), suggesting that some form of adaptation to the densovirus is occurring in these mosquitoes.…”