Confirmed case of encephalitis caused by Murray Valley encephalitis virus infection in a horse

A five year old Australian stock horse in Monto, Queensland, developed neurological signs and was euthanized after a six day course of illness. Histological examination of the brain and spinal cord revealed moderate to severe, subacute, non-suppurative encephalomyelitis. Sections of spinal cord stained positively in immunohistochemistry with a flavivirus-specific monoclonal antibody. Reverse transcription-polymerase chain reaction assay targeting the envelope gene of flavivirus yielded positive results from brain, spinal cord, cerebrospinal fluid and facial nerve. A flavivirus was isolated from the cerebrum and spinal cord. Nucleotide sequences obtained from amplicons from both tissues and virus isolated in cell culture were compared with those in GenBank, and had 96-98% identity with Murray Valley encephalitis virus. The partial envelope gene sequence of the viral isolate clustered into Genotype 1, and was most closely related to a previous Queensland isolate. This is the first confirmed case of naturally-occurring equine encephalitis attributable to Murray Valley encephalitis virus infection

Biochemical characterisation of Murray Valley encephalitis virus proteinase

AbstractMurray Valley encephalitis virus (MVEV) is a member of the flavivirus group, a large family of single stranded RNA viruses, which cause serious disease in all regions of the world. Its genome encodes a large polyprotein which is processed by both host proteinases and a virally encoded serine proteinase, non-structural protein 3 (NS3). NS3, an essential viral enzyme, requires another virally encoded protein cofactor, NS2B, for proteolytic activity. The cloning, expression and biochemical characterisation of a stable MVEV NS2B–NS3 fusion protein is described

The role of genetic diversity in the replication, pathogenicity and virulence of Murray Valley encephalitis virus

Genetic and phenotypic variation of genotype 1 (G1) and genotype 2 (G2) Murray valley encephalitis virus (MVEV) were characterised. G2 viruses were a minority, had lower levels of genetic diversity and an attenuated phenotype in the mouse model of MVE. G1 isolates were abundant with higher levels of genetic diversity and a virulent phenotype. The restricted evolution of MVEV was due to multiplication in mosquito cells. An RT-qPCR assay detecting all MVEV genotypes was developed

Murray Valley encephalitis virus surveillance and control initiatives in Australia.

Mechanisms for monitoring Murray Valley encephalitis (MVE) virus activity include surveillance of human cases, surveillance for activity in sentinel animals, monitoring of mosquito vectors and monitoring of weather conditions. The monitoring of human cases is only one possible trigger for public health action and the additional surveillance systems are used in concert to signal the risk of human disease, often before the appearance of human cases. Mosquito vector surveillance includes mosquito trapping for speciation and enumeration of mosquitoes to monitor population sizes and relative composition. Virus isolation from mosquitoes can also be undertaken. Monitoring of weather conditions and vector surveillance determines whether there is a potential for MVE activity to occur. Virus isolation from trapped mosquitoes is necessary to define whether MVE is actually present, but is difficult to deliver in a timely fashion in some jurisdictions. Monitoring of sentinel animals indicates whether MVE transmission to vertebrates is actually occurring. Meteorological surveillance can assist in the prediction of potential MVE virus activity by signalling conditions that have been associated with outbreaks of Murray Valley encephalitis in humans in the past. Predictive models of MVE virus activity for south-eastern Australia have been developed, but due to the infrequency of outbreaks, are yet to be demonstrated as useful for the forecasting of major outbreaks. Surveillance mechanisms vary across the jurisdictions. Surveillance of human disease occurs in all States and Territories by reporting of cases to health authorities. Sentinel flocks of chickens are maintained in 4 jurisdictions (Western Australia, the Northern Territory, Victoria and New South Wales) with collaborations between Western Australia and the Northern Territory. Mosquito monitoring complements the surveillance of sentinel animals in these jurisdictions. In addition, other mosquito monitoring programs exist in other States (including South Australia and Queensland). Public health control measures may include advice to the general public and mosquito management programs to reduce the numbers of both mosquito larvae and adult vectors. Strategic plans for public health action in the event of MVE virus activity are currently developed or being developed in New South Wales, the Northern Territory, South Australia, Western Australia and Victoria. A southern tri-State agreement exists between health departments of New South Wales, Victoria and South Australia and the Commonwealth Department of Health and Aged Care. All partners have agreed to co-operate and provide assistance in predicting and combatting outbreaks of mosquito-borne disease in south-eastern Australia. The newly formed National Arbovirus Advisory Committee is a working party providing advice to the Communicable Diseases Network Australia on arbovirus surveillance and control. Recommendations for further enhancement of national surveillance for Murray Valley encephalitis are described

Theoretical study of the Usutu virus helicase 3D structure, by means of computer-aided homology modelling

<p>Abstract</p> <p>Background</p> <p>Usutu virus belongs to the <it>Flaviviridae </it>viral family and constitutes an important pathogen. The viral helicase is an ideal target for inhibitor design, since this enzyme is essential for the survival, proliferation and transmission of the virus.</p> <p>Results</p> <p>Towards a drug-design approach, the 3D model of the Usutu virus helicase structure has been designed, using conventional homology modelling techniques and the known 3D-structure of the Murray Valley Encephalitis virus helicase, of the same viral family, as template. The model was then subjected to extended molecular dynamics simulations in a periodic box, filled with explicit water molecules for 10 nanoseconds. The reliability of the model was confirmed by obtaining acceptable scores from a variety of <it>in silico </it>scoring tools, including Procheck and Verify3D.</p> <p>Conlcusion</p> <p>The 3D model of the Usutu virus helicase exhibits <it>in silico </it>all known structural characteristics of the <it>Flaviviridae </it>viral family helicase enzymes and could provide the platform for further <it>de novo </it>structure-based design of novel anti-Usutu agents.</p

The Molecular Epidemiology and Evolution of Murray Valley Encephalitis Virus: Recent Emergence of Distinct Sub-lineages of the Dominant Genotype 1

© 2015 Williams et al. Background: Recent increased activity of the mosquito-borne Murray Valley encephalitis virus (MVEV) in Australia has renewed concerns regarding its potential to spread and cause disease. Methodology/Principal Findings: To better understand the genetic relationships between earlier and more recent circulating strains, patterns of virus movement, as well as the molecular basis of MVEV evolution, complete pre-membrane (prM) and Envelope (Env) genes were sequenced from sixty-six MVEV strains from different regions of the Australasian region, isolated over a sixty year period (1951–2011). Phylogenetic analyses indicated that, of the four recognized genotypes, only G1 and G2 are contemporary. G1 viruses were dominant over the sampling period and found across the known geographic range of MVEV. Two distinct sub-lineages of G1 were observed (1A and 1B). Although G1B strains have been isolated from across mainland Australia, Australian G1A strains have not been detected outside northwest Australia. Similarly, G2 is comprised of only Western Australian isolates from mosquitoes, suggesting G1B and G2 viruses have geographic or ecological restrictions. No evidence of recombination was found and a single amino acid substitution in the Env protein (S332G) was found to be under positive selection, while several others were found to be under directional evolution. Evolutionary analyses indicated that extant genotypes of MVEV began to diverge from a common ancestor approximately 200 years ago. G2 was the first genotype to diverge, followed by G3 and G4, and finally G1, from which subtypes G1A and G1B diverged between 1964 and 1994. Conclusions/Significance: The results of this study provides new insights into the genetic diversity and evolution of MVEV. The demonstration of co-circulation of all contemporary genetic lineages of MVEV in northwestern Australia, supports the contention that this region is the enzootic focus for this virus

Australian encephalitis: sentinel chicken surveillance programme

Sentinel chicken flocks are used to monitor flavivirus activity in Australia. The main viruses of concern are Murray Valley encephalitis (MVE) and Kunjin which cause the potentially fatal disease encephalitis, in humans. Currently 30 flocks are maintained in the north of Western Australia, 9 in the Northern Territory, 12 in New South Wales and 10 in Victoria. The flocks in Western Australia and the Northern Territory are tested year round but those in New South Wales and Victoria are tested only from November to March, during the main risk season. Results are coordinated by the Arbovirus Laboratory in Perth and reported bimonthly