Shrimp Parvovirus Circular DNA Fragments Arise From Both Endogenous Viral Elements and the Infecting Virus.

Some insects use endogenous reverse transcriptase (RT) to make variable viral copy DNA (vcDNA) fragments from viral RNA in linear (lvcDNA) and circular (cvcDNA) forms. The latter form is easy to extract selectively. The vcDNA produces small interfering RNA (siRNA) variants that inhibit viral replication via the RNA interference (RNAi) pathway. The vcDNA is also autonomously inserted into the host genome as endogenous viral elements (EVE) that can also result in RNAi. We hypothesized that similar mechanisms occurred in shrimp. We used the insect methods to extract circular viral copy DNA (cvcDNA) from the giant tiger shrimp (Penaeus monodon) infected with a virus originally named infectious hypodermal and hematopoietic necrosis virus (IHHNV). Simultaneous injection of the extracted cvcDNA plus IHHNV into whiteleg shrimp (Penaeus vannamei) resulted in a significant reduction in IHHNV replication when compared to shrimp injected with IHHNV only. Next generation sequencing (NGS) revealed that the extract contained a mixture of two general IHHNV-cvcDNA types. One showed 98 to 99% sequence identity to GenBank record AF218266 from an extant type of infectious IHHNV. The other type showed 98% sequence identity to GenBank record DQ228358, an EVE formerly called non-infectious IHHNV. The startling discovery that EVE could also give rise to cvcDNA revealed that cvcDNA provided an easy means to identify and characterize EVE in shrimp and perhaps other organisms. These studies open the way for identification, characterization and use of protective cvcDNA as a potential shrimp vaccine and as a tool to identify, characterize and select naturally protective EVE to improve shrimp tolerance to homologous viruses in breeding programs.

History and current status of development and use of viral insecticides in China.

The use of insect viruses as biological control agents started in the early 1960s in China. To date, more than 32 viruses have been used to control insect pests in agriculture, forestry, pastures, and domestic gardens in China. In 2014, 57 products from 11 viruses were authorized as commercial viral insecticides by the Ministry of Agriculture of China. Approximately 1600 tons of viral insecticidal formulations have been produced annually in recent years, accounting for about 0.2% of the total insecticide output of China. The development and use of Helicoverpa armigera nucleopolyhedrovirus, Mamestra brassicae nucleopolyhedrovirus, Spodoptera litura nucleopolyhedrovirus, and Periplaneta fuliginosa densovirus are discussed as case studies. Additionally, some baculoviruses have been genetically modified to improve their killing rate, infectivity, and ultraviolet resistance. In this context, the biosafety assessment of a genetically modified Helicoverpa armigera nucleopolyhedrovirus is discussed.

Distribución espacial y temporal de los sitios de cría de aedes albopictus (Diptera: Culicidae) en La Habana, Cuba / Spatial and temporal distribution of breeding sites of aedes albopictus (Diptera: Culicidae) in Havana, Cuba

INTRODUCCIÓN: Aedes albopictus es un mosquito originario de las selvas del sudeste de Asia, que en las últimas décadas está extendiéndose a todos los continentes. Ésta especie se registró por primera vez en Cuba en la provincia La Habana en 1995. OBJETIVO: determinar la distribución espacial y temporal de los sitios de cría de Ae. albopictus en los municipios de la provincia de La Habana durante el 2011 y 2012. MÉTODOS: se realizó el muestreo de todos los depósitos conteniendo agua en los bloques o manzanas, así como, en los terrenos baldíos presentes en las áreas urbanas y peri urbanos del universo de cada municipio que compone la provinciaLa Habana. RESULTADOS: Ae. albopictus se registró en 13 de los 15 municipios del área estudiada, lo que evidencia además de su introducción su dispersión en el área. Se encontró una mayor presencia de Ae. albopictus en los municipios periféricos tales como Playa, La Lisa, Boyeros, Arroyo Naranjo, Cotorro, Guanabacoa y Habana del Este.Se encontró un incremento en el total de muestras en el 2012 con respecto al 2011notándose en ambos años un incremento a partir de junio hasta octubre. La mayor cantidad de muestras de Ae. albopictus con más de una especie de culícido correspondieron en ambos años a los meses de lluvia (mayo-septiembre). CONCLUSIONES: se constató la presencia y distribución de Ae. albopictus en La Habana favorecido por las condiciones ecológicas existentes y la disponibilidad de sitios de cría(AU)

INTRODUCTION: Aedes albopictus is a mosquito native to the forests of Southeast Asia which has spread to all continents in recent decades. The species was first reported in Cuba in the province of Havana in 1995. OBJECTIVE: determine the spatial and temporal distribution of breeding sites of Ae. albopictus in the municipalities of the province of Havana in 2011 and 2012. METHODS: sampling was conducted of all containers with water in residential areas and vacant lots of urban and suburban zones of all municipalities in the province of Havana. RESULTS: presence of Ae. albopictus was reported in 13 of the 15 municipalities in the study area, revealing not only its introduction but also its spread in the area. The greatest presence of Ae. albopictus was found in peripheral municipalities like Playa, La Lisa, Boyeros, Arroyo Naranjo, Cotorro, Guanabacoa and Habana del Este. An increase in the total number of samples was observed in 2012 with respect to 2011. In both years there was an increase from June to October. Again in both years, the greatest number of samples of Ae. albopictus with more than one culicid species was found in the rainy season (May to September). CONCLUSIONS: the presence and distribution of Ae. albopictus in Havana was confirmed. Favorable ecological conditions and the availability of breeding sites play a decisive role in such presence and distribution(AU)

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.

Evaluation of mosquito densoviruses for controlling Aedes aegypti (Diptera: Culicidae): variation in efficiency due to virus strain and geographic origin of mosquitoes.

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.

Seasonal prevalence of Aedes aegypti immatures in Kolkata, India.

Dengue and dengue hemorrhagic fever (DHF) is recurring in India in recent years, affecting many cities including Kolkata (Calcutta). In view of this, a survey of three years was carried out on the prevalence of immatures of the vector mosquito Aedes aegypti in the city of Kolkata. Mosquito immatures were found throughout the year with fluctuating densities in the habitats surveyed. An index of density of immatures (I/S)m employed in the study revealed that in the months of August and September a peak in abundance occurs, irrespective of the habitats, with the values ranging between 1.12 and 11.4. The (I/S)m values were low during the months of April and May ranging between 0.4 and 3.8. As larval habitats, earthen containers and the sewage drains were positive throughout the year, while during the months of December to February, air-coolers and conditioners as habitats remained totally dry, without immature Ae. aegypti. The number of positive sites and monthly density between the habitat types were significantly different with an I/S- value (for a year) ranging between 2.64 (air-coolers) and 4.97 (earthen containers). The survey, while providing preliminary baseline data on immature abundance in Kolkata, calls for continuous entomological surveillance using standard protocols as carried out in Thailand for the vector management program against dengue.

Mosquito densonucleosis viruses cause dramatically different infection phenotypes in the C6/36 Aedes albopictus cell line.

Mosquito densoviruses generally establish persistent infections in mosquito cell lines including the C6/36 Aedes albopictus cell line. In contrast, the closely related Haemagogus equinus densovirus (HeDNV) causes dramatic cytopathic effects in the C6/36 Aedes albopictus cell line. Infection of C6/36 cells by HeDNV causes internucleosomal fragmentation of host chromosomal DNA, changes in cellular morphology (membrane budding, apoptotic bodies), caspase activation and exposure of phosphatidylserine on the cellular membrane. This is accompanied by a higher rate of infection and more vigorous production of virus in these cells. These observations are consistent with the induction of apoptosis during infection. In contrast, expression of AeDNV proteins in C6/36 cells does not cause obvious cytopathic effects although NS1 expression causes accumulation of cells in G2 phase. C6/36 cells persistently infected with AeDNV were not protected from superinfection with HeDNV. Thus, there does not seem to be an antiviral state induced by AeDNV persistent infection.