A large scale laboratory cage trial of Aedes densonucleosis virus (AeDNV).

Aedes aegypti (L.) (Diptera: Culicidae) the primary vector of dengue viruses (DENV1-4), oviposit in and around human dwellings, including sites difficult to locate, making control of this mosquito challenging. We explored the efficacy and sustainability of Aedes Densonucleosis Virus (AeDNV) as a biocontrol agent for Ae. aegypti in and among oviposition sites in large laboratory cages (> 92 m3) as a prelude to field trials. Select cages were seeded with AeDNV in a single oviposition site (OPS) with unseeded OPSs established at varied distances. Quantitative real-time polymerase chain reaction was used to track dispersal and accumulation of AeDNV among OPSs. All eggs were collected weekly from each cage and counted. We asked: (1) Is AeDNV dispersed over varying distances and can it accumulate and persist in novel OPSs? (2) Are egg densities reduced in AeDNV treated populations? AeDNV was dispersed to and sustained in novel OPSs. Virus accumulation in OPSs was positively correlated with egg densities and proximity to the initial infection source affected the timing of dispersal and maintenance of viral titers. AeDNV did not significantly reduce Ae. aegypti egg densities. The current study documents that adult female Ae. aegypti oviposition behavior leads to successful viral dispersal from treated to novel containers in large-scale cages; however, the AeDNV titers reached were not sufficient to reduce egg densities.

Aedes aegypti densonucleosis virus amplifies, spreads, and reduces host populations in laboratory cage studies.

Aedes densonucleosis virus (family Parcoviridae, genus Brevidensovirus, AeDNV) is a mosquito pathogen that increases Aedes aegypti larval mortality and reduces adult life span. We conducted three laboratory population cage trials, each lasting 16-25 wk. We tested two broad hypotheses. First, Ae. aegypti raised in containers seeded with 10(8) AeDNV genome equivalents/ml (geq/ ml), a concentration feasible for field application, increase AeDNV to concentrations that cause significant adult and larval mortality. Second, infected female mosquitoes disperse AeDNV to uninfected larval habitats. In hypothesis 1, we addressed the rate at which infected larvae secrete virus, how AeDNV titers change in seeded containers over time, whether AeDNV decays over time, and whether AeDNV exposed populations are reduced. In hypothesis 2, we monitored AeDNV concentrations in novel containers after oviposition by infected females. Both hypotheses were supported. Larvae increased AeDNV, secreting virus at a rate of 2.14 x 10(6) geq/larva/d when exposed to 10(8) geq/ml. AeDNV titers reached an asymptote of 10(10) geq/ml by week 10 in seeded containers. AeDNV decayed by 1 log every 4 d as indicated by a reduction in larval mortality. Adult population size was reduced in treated populations. Infected females dispersed AeDNV to novel containers, with titers reaching 10(8) geq/ml. The parameters were used in a Leslie-Lewis matrix model. This model predicted that AeDNV negatively affects Ae. aegypti densities and population structure and thus vectorial capacity.

Infection and pathogenicity of the mosquito densoviruses AeDNV, HeDNV, and APeDNV in Aedes aegypti mosquitoes (Diptera: Culicidae).

These studies compared three genetically distinct mosquito densoviruses Aedes aegypti (AeDNV), Hemagogus equinus (HeDNV), and Aedes Peruvian (APeDNV) densoviruses in a laboratory investigation to begin to evaluate their potential as mosquito control agents. A real-time polymerase chain reaction (PCR) assay for quantification of viral genomes and a standardized mosquito infection protocol were developed. Mortality associated with exposure to AeDNV increased in a dose-dependent manner, with the maximum mortality of 75.1% occurring in those organisms exposed to the highest dose of virus. The majority of death occurred as larvae. Similar results were observed with AeDNV produced from ground larvae and AeDNV produced from cell culture. Exposure of mosquitoes to HeDNV and APeDNV resulted in lower mortality, with values peaking at 33.5% for HeDNV and 27.8% for APeDNV. AeDNV-exposed larvae develop at a slower rate than nonexposed and HeDNV- and APeDNV-exposed larvae. Decreased virulence does not reflect a decrease in virus replication. PCR analysis of infectivity rates and titers in adults revealed reproduction of all three viruses, with an average viral titer of approximately 10 logs/mosquito after exposure to the highest dose of each virus. Accumulation of virus in the larval-rearing water was also observed with values approaching 10-11 logs/ml for each virus. These data indicate that there are dramatic differences in the pathogenicity among mosquito densoviruses.