Molecular Epidemiology of Mayaro Virus among Febrile Patients, Roraima State, Brazil, 2018-2021

We detected Mayaro virus (MAYV) in 3.4% (28/822) of febrile patients tested during 2018-2021 from Roraima State, Brazil. We also isolated MAYV strains and confirmed that these cases were caused by genotype D. Improved surveillance is needed to better determine the burden of MAYV in the Amazon Region.

Alphavirus Identification in Neotropical Bats

Alphaviruses (Togaviridae) are arthropod-borne viruses responsible for several emerging diseases, maintained in nature through transmission between hematophagous arthropod vectors and susceptible vertebrate hosts. Although bats harbor many species of viruses, their role as reservoir hosts in emergent zoonoses has been verified only in a few cases. With bats being the second most diverse order of mammals, their implication in arbovirus infections needs to be elucidated. Reports on arbovirus infections in bats are scarce, especially in South American indigenous species. In this work, we report the genomic detection and identification of two different alphaviruses in oral swabs from bats captured in Northern Uruguay. Phylogenetic analysis identified Río Negro virus (RNV) in two different species: Tadarida brasiliensis (n = 6) and Myotis spp. (n = 1) and eastern equine encephalitis virus (EEEV) in Myotis spp. (n = 2). Previous studies of our group identified RNV and EEEV in mosquitoes and horse serology, suggesting that they may be circulating in enzootic cycles in our country. Our findings reveal that bats can be infected by these arboviruses and that chiropterans could participate in the viral natural cycle as virus amplifiers or dead-end hosts. Further studies are warranted to elucidate the role of these mammals in the biological cycle of these alphaviruses in Uruguay.

Genomic Epidemiology of Salmonid Alphavirus in Norwegian Aquaculture Reveals Recent Subtype-2 Transmission Dynamics and Novel Subtype-3 Lineages

Viral disease poses a major barrier to sustainable aquaculture, with outbreaks causing large economic losses and growing concerns for fish welfare. Genomic epidemiology can support disease control by providing rapid inferences on viral evolution and disease transmission. In this study, genomic epidemiology was used to investigate salmonid alphavirus (SAV), the causative agent of pancreas disease (PD) in Atlantic salmon. Our aim was to reconstruct SAV subtype-2 (SAV2) diversity and transmission dynamics in recent Norwegian aquaculture, including the origin of SAV2 in regions where this subtype is not tolerated under current legislation. Using nanopore sequencing, we captured ~90% of the SAV2 genome for n = 68 field isolates from 10 aquaculture production regions sampled between 2018 and 2020. Using time-calibrated phylogenetics, we infer that, following its introduction to Norway around 2010, SAV2 split into two clades (SAV2a and 2b) around 2013. While co-present at the same sites near the boundary of Møre og Romsdal and Trøndelag, SAV2a and 2b were generally detected in non-overlapping locations at more Southern and Northern latitudes, respectively. We provide evidence for recent SAV2 transmission over large distances, revealing a strong connection between Møre og Romsdal and SAV2 detected in 2019/20 in Rogaland. We also demonstrate separate introductions of SAV2a and 2b outside the SAV2 zone in Sognefjorden (Vestland), connected to samples from Møre og Romsdal and Trøndelag, respectively, and a likely 100 km Northward transmission of SAV2b within Trøndelag. Finally, we recovered genomes of SAV2a and SAV3 co-infecting single fish in Rogaland, involving novel SAV3 lineages that diverged from previously characterized strains >25 years ago. Overall, this study demonstrates useful applications of genomic epidemiology for tracking viral disease spread in aquaculture.

Genetically modified attenuated salmonid alphavirus: A potential strategy for immunization of Atlantic salmon

Pancreas disease (PD) is a serious challenge in European salmonid aquaculture caused by salmonid alphavirus (SAV). In this study, we report the effect of immunization of Atlantic salmon with three attenuated infectious SAV3 strains with targeted mutations in a glycosylation site of the envelope E2 protein and/or in a nuclear localization signal in the capsid protein. In a pilot experiment, it was shown that the mutated viral strains replicated in fish, transmitted to naïve cohabitants and that the transmission had not altered the sequences. In the main experiment, the fish were immunized with the strains and challenged with SAV3 eight weeks after immunization. Immunization resulted in infection both in injected fish and 2 weeks later in the cohabitant fish, followed by a persistent but declining load of the mutated virus variants in the hearts. The immunized fish developed clinical signs and pathology consistent with PD prior to challenge. However, fish injected with the virus mutated in both E2 and capsid showed little clinical signs and had higher average weight gain than the groups immunized with the single mutated variants. The SAV strain used for challenge was not detected in the immunized fish indicating that these fish were protected against superinfection with SAV during the 12 weeks of the experiment.

The epidemiology of Mayaro virus in the Americas: A systematic review and key parameter estimates for outbreak modelling

Mayaro virus (MAYV) is an arbovirus that is endemic to tropical forests in Central and South America, particularly within the Amazon basin. In recent years, concern has increased regarding MAYV's ability to invade urban areas and cause epidemics across the region. We conducted a systematic literature review to characterise the evolutionary history of MAYV, its transmission potential, and exposure patterns to the virus. We analysed data from the literature on MAYV infection to produce estimates of key epidemiological parameters, including the generation time and the basic reproduction number, R0. We also estimated the force-of-infection (FOI) in epidemic and endemic settings. Seventy-six publications met our inclusion criteria. Evidence of MAYV infection in humans, animals, or vectors was reported in 14 Latin American countries. Nine countries reported evidence of acute infection in humans confirmed by viral isolation or reverse transcription-PCR (RT-PCR). We identified at least five MAYV outbreaks. Seroprevalence from population based cross-sectional studies ranged from 21% to 72%. The estimated mean generation time of MAYV was 15.2 days (95% CrI: 11.7-19.8) with a standard deviation of 6.3 days (95% CrI: 4.2-9.5). The per-capita risk of MAYV infection (FOI) ranged between 0.01 and 0.05 per year. The mean R0 estimates ranged between 2.1 and 2.9 in the Amazon basin areas and between 1.1 and 1.3 in the regions outside of the Amazon basin. Although MAYV has been identified in urban vectors, there is not yet evidence of sustained urban transmission. MAYV's enzootic cycle could become established in forested areas within cities similar to yellow fever virus.

Isolation and phylogenetic analysis of Getah virus from a commercial modified live vaccine against porcine reproductive and respiratory syndrome virus

In the present study, Getah virus (GETV) isolate, GETV-V1, was isolated from a commercial PRRSV attenuated live vaccine (MLV), which has been widely used to immunize pigs against porcine reproductive and respiratory syndrome virus (PRRSV). Further analysis demonstrated that nine batches of the PRRSV MLV vaccine (three batches per year from 2017 to 2019) from the same manufacturer were all positive for GETV. Genomic analyses indicated that the GETV-V1 isolate shared the highest sequence identity with the GETV strain, 16-I-674, which was isolated from horses in Japan. The phylogenetic analysis based on the genomic sequences showed that the GETV-V1 strain was clustered with the Japanese GETV strains. Taken together, this is the first report of GETV contamination in live swine vaccines in China. Our findings demonstrate that immunization with commercial live vaccines might be a potential novel route of GETV transmission in swine. This highlights the need for more extensive monitoring of commercial live vaccines.

A survey of RNA viruses in mosquitoes from Mozambique reveals novel genetic lineages of flaviviruses and phenuiviruses, as well as frequent flavivirus-like viral DNA forms in Mansonia

BACKGROUND

Mosquito-borne diseases involving arboviruses represent expanding threats to sub-Saharan Africa imposing as considerable burden to human and veterinary public health. In Mozambique over one hundred species of potential arbovirus mosquito vectors have been identified, although their precise role in maintaining such viruses in circulation in the country remains to be elucidated. The aim of this study was to screen for the presence of flaviviruses, alphaviruses and bunyaviruses in mosquitoes from different regions of Mozambique.

RESULTS

Our survey analyzed 14,519 mosquitoes, and the results obtained revealed genetically distinct insect-specific flaviviruses, detected in multiple species of mosquitoes from different genera. In addition, smaller flavivirus-like NS5 sequences, frequently detected in Mansonia seemed to correspond to defective viral sequences, present as viral DNA forms. Furthermore, three lineages of putative members of the Phenuiviridae family were also detected, two of which apparently corresponding to novel viral genetic lineages.

CONCLUSION

This study reports for the first-time novel insect-specific flaviviruses and novel phenuiviruses, as well as frequent flavivirus-like viral DNA forms in several widely known vector species. This unique work represents recent investigation of virus screening conducted in mosquitoes from Mozambique and an important contribution to inform the establishment of a vector control program for arbovirus in the country and in the region.

Highly Pathogenic Swine Getah Virus in Blue Foxes, Eastern China, 2017

We isolated Getah virus from infected foxes in Shandong Province, eastern China. We sequenced the complete Getah virus genome, and phylogenetic analysis revealed a close relationship with a highly pathogenic swine epidemic strain in China. Epidemiologic investigation showed that pigs might play a pivotal role in disease transmission to foxes.

Divergent Barmah Forest Virus from Papua New Guinea

We report a case of Barmah Forest virus infection in a child from Central Province, Papua New Guinea, who had no previous travel history. Genomic characterization of the virus showed divergent origin compared with viruses previously detected, supporting the hypothesis that the range of Barmah Forest virus extends beyond Australia.

Isolation of salmonid alphavirus subtype 6 from wild-caught ballan wrasse, Labrus bergylta (Ascanius)

The use of cleaner fish as a biological control for sea lice in Atlantic salmon aquaculture has increased in recent years. Wild-caught wrasse are commonly used as cleaner fish in Europe. In Ireland, samples of wrasse from each fishing area are screened for potential pathogens prior to their deployment into sea cages. Salmonid alphavirus was isolated from a pooled sample of ballan wrasse, showing no signs of disease, caught from the NW of Ireland. Partial sequencing of the E2 and nsP3 genes showed that it was closely related to the previously reported SAV subtype 6. This represents only the second isolation of this subtype and the first from a wild fish species, namely ballan wrasse.

Serological and spatial analysis of alphavirus and flavivirus prevalence and risk factors in a rural community in western Kenya

Alphaviruses, such as chikungunya virus, and flaviviruses, such as dengue virus, are (re)-emerging arboviruses that are endemic in tropical environments. In Africa, arbovirus infections are often undiagnosed and unreported, with febrile illnesses often assumed to be malaria. This cross-sectional study aimed to characterize the seroprevalence of alphaviruses and flaviviruses among children (ages 5-14, n = 250) and adults (ages 15 ≥ 75, n = 250) in western Kenya. Risk factors for seropositivity were explored using Lasso regression. Overall, 67% of participants showed alphavirus seropositivity (CI95 63%-70%), and 1.6% of participants showed flavivirus seropositivity (CI95 0.7%-3%). Children aged 10-14 were more likely to be seropositive to an alphavirus than adults (p < 0.001), suggesting a recent transmission period. Alphavirus and flavivirus seropositivity was detected in the youngest participants (age 5-9), providing evidence of inter-epidemic transmission. Demographic variables that were significantly different amongst those with previous infection versus those without infection included age, education level, and occupation. Behavioral and environmental variables significantly different amongst those in with previous infection to those without infection included taking animals for grazing, fishing, and recent village flooding. Experience of recent fever was also found to be a significant indicator of infection (p = 0.027). These results confirm alphavirus and flavivirus exposure in western Kenya, while illustrating significantly higher alphavirus transmission compared to previous studies.

Disentangling the Frames, the State of Research on the Alphavirus 6K and TF Proteins

For 30 years it was thought the alphavirus 6K gene encoded a single 6 kDa protein. However, through a bioinformatics search 10 years ago, it was discovered that there is a frameshifting event and two proteins, 6K and transframe (TF), are translated from the 6K gene. Thus, many functions attributed to the 6K protein needed reevaluation to determine if they properly belong to 6K, TF, or both proteins. In this mini-review, we reevaluate the past research on 6K and put those results in context where there are two proteins, 6K and TF, instead of one. Additionally, we discuss the most cogent outstanding questions for 6K and TF research, including their collective importance in alphavirus budding and their potential importance in disease based on the latest virulence data.

The Envelope Proteins of the Bunyavirales

The Bunyavirales Order encompasses nine families of enveloped viruses containing a single-stranded negative-sense RNA genome divided into three segments. The small (S) and large (L) segments encode proteins participating in genome replication in the infected cell cytoplasm. The middle (M) segment encodes the viral glycoproteins Gn and Gc, which are derived from a precursor polyprotein by host cell proteases. Entry studies are available only for a few viruses in the Order, and in each case they were shown to enter cells via receptor-mediated endocytosis. The acidic endosomal pH triggers the fusion of the viral envelope with the membrane of an endosome. Structural studies on two members of this Order, the phleboviruses and the hantaviruses, have shown that the membrane fusion protein Gc displays a class II fusion protein fold and is homologous to its counterparts in flaviviruses and alphaviruses, which are positive-sense, single-stranded RNA viruses. We analyze here recent data on the structure and function of the structure of the phlebovirus Gc and hantavirus Gn and Gc glycoproteins, and extrapolate common features identified in the amino acid sequences to understand also the structure and function of their counterparts in other families of the Bunyavirales Order. Our analysis also identified clear structural homology between the hantavirus Gn and alphavirus E2 glycoproteins, which make a heterodimer with the corresponding fusion proteins Gc and E1, respectively, revealing that not only the fusion protein has been conserved across viral families.

Mosquito-transmitted viruses - the great Brazilian challenge

Arboviruses pose a serious threat to public health worldwide, overloading the healthcare system and causing economic losses. These viruses form a very diverse group, and in Brazil, arboviruses belonging to the families Flaviviridae and Togaviridae are predominant. Unfortunately, the number of arboviruses increases in proportion with factors such as deforestation, poor sanitation, climate changes, and introduction of new viruses like Chikungunya virus and Zika virus. In Brazil, dengue is endemic, along with the presence of other arboviruses. The situation is complicated by the scarcity of diagnostic infrastructure and the absence of approved vaccines for these diseases. Disease control, thus, relies solely on vector control. Therefore, enhanced clinical knowledge and improved general awareness about these arboviruses are indispensable to tackle diagnostic inadequacies.

Occurrence of salmonid alphavirus (SAV) and piscine orthoreovirus (PRV) infections in wild sea trout Salmo trutta in Norway

Viral diseases represent a serious problem in Atlantic salmon (Salmo salar L.) farming in Norway. Pancreas disease (PD) caused by salmonid alphavirus (SAV) and heart and skeletal muscle inflammation (HSMI) caused by piscine orthoreovirus (PRV) are among the most frequently diagnosed viral diseases in recent years. The possible spread of viruses from salmon farms to wild fish is a major public concern. Sea trout S. trutta collected from the major farming areas along the Norwegian coast are likely to have been exposed to SAV and PRV from farms with disease outbreaks. We examined 843 sea trout from 4 counties in Norway for SAV and PRV infections. We did not detect SAV in any of the tested fish, although significant numbers of the trout were caught in areas with frequent PD outbreaks. Low levels of PRV were detected in 1.3% of the sea trout. PRV-infected sea trout were caught in both salmon farming and non-farming areas, so the occurrence of infections was not associated with farming intensity or HSMI cases. Our results suggest that SAV and PRV infections are uncommon in wild sea trout. Hence, we found no evidence that sea trout are at risk from SAV or PRV released from salmon farms.

Genetic characterization of salmonid alphavirus in Norway

Pancreas disease (PD), caused by salmonid alphavirus subtype 3 (SAV3), emerged in Norwegian aquaculture in the 1980s and is now endemic along the south-western coast. In 2011, the first cases of PD caused by marine salmonid alphavirus subtype 2 (SAV2) were reported. This subtype has spread rapidly among the fish farms outside the PD-endemic zone and is responsible for disease outbreaks at an increasing numbers of sites. To describe the geographical distribution of salmonid alphavirus (SAV), and to assess the time and site of introduction of marine SAV2 to Norway, an extensive genetic characterization including more than 200 SAV-positive samples from 157 Norwegian marine production sites collected from May 2007 to December 2012 was executed. The first samples positive for marine SAV2 originated from Romsdal, in June 2010. Sequence analysis of the E2 gene revealed that all marine SAV2 included in this study were nearly identical, suggesting a single introduction into Norwegian aquaculture. Further, this study provides evidence of a separate geographical distribution of two subtypes in Norway. SAV3 is present in south-western Norway, and marine SAV2 circulates in north-western and Mid-Norway, a geographical area which since 2010 constitutes the endemic zone for marine SAV2.

Getah Virus Infection among Racehorses, Japan, 2014

An outbreak of Getah virus infection occurred among racehorses in Japan during September and October 2014. Of 49 febrile horses tested by reverse transcription PCR, 25 were positive for Getah virus. Viruses detected in 2014 were phylogenetically different from the virus isolated in Japan in 1978.

Clinical manifestations of pancreas disease outbreaks in Norwegian marine salmon farming - variations due to salmonid alphavirus subtype

Pancreas disease (PD) in Norwegian salmonid aquaculture has traditionally been caused by salmonid alphavirus (SAV) subtype 3. Following the isolation of a novel SAV subtype in 2010, marine SAV2, two separate endemic areas have developed. It has been debated whether disease outbreaks due to marine SAV2 result in milder clinical manifestations compared to outbreaks caused by SAV3. The aim of this study was to descriptively investigate site-level differences in the clinical manifestations of marine SAV2 and SAV3 at Norwegian seawater sites diagnosed with PD in 2012. The findings suggest that Norwegian PD outbreaks caused by marine SAV2 result in lower mortality and milder clinical signs compared to outbreaks caused by SAV3. For sites without reported PD-related mortality, there was no difference in the mortality levels between sites infected by marine SAV2 and SAV3. The results also indicate that there are no differences in grading quality at slaughter between the SAV subtypes.

First outbreak of sleeping disease in Switzerland: disease signs and virus characterization

Sleeping disease is a contagious disease mainly of freshwater farmed rainbow trout, caused by salmonid alphavirus (SAV) Subtype 2. Here we describe the first case in Switzerland. Pathological changes ranged from acute pancreas necrosis to more chronic lesions with complete loss of exocrine pancreas and simultaneous degenerative, inflammatory and regenerative heart and muscle lesions. The partial sequencing of SAV E2 and nsp3 genes placed the Swiss SAV variant within the Subtype 2 clustering together with freshwater isolates from UK and continental Europe. Although mortality stayed low, growth rates were significantly reduced, making the disease economically relevant.

Cross-neutralization studies with salmonid alphavirus subtype 1-6 strains: results with sera from experimental studies and natural infections

The serological reactivity between strains of each of the six currently genetically defined subtypes of salmonid alphavirus (SAV) was examined by comparison of homologous and heterologous virus neutralization titres on sera from experimentally infected fish. With the exception of the level of SAV subtype 6 neutralization by heterologous sera, good cross-neutralization was detected between all subtypes, albeit with variation in geometric mean titres when each subtype-specific serum set was tested against the panel of virus subtypes. A similar pattern was evident with field sera, except that heterologous neutralization of the SAV6 strain was more evident. In only 23% of available pairwise comparisons was the homologous titre recorded with an experimentally derived serum fourfold or greater than the heterologous titre, and in only two instances was this difference demonstrated in both directions. No virus strains consistently met the old serology-based criteria (Sub-committee on Inter-relationships Among Catalogued Alphaviruses) to be considered separate subtypes within an alphavirus species. Only when testing with an SAV subtype-2-specific monoclonal antibody was a major difference between homologous and heterologous neutralization capacity evident. These results provide new direct or indirect information in terms of SAV classification, vaccine efficacy and the selection and validation of reagents for serological and immunological diagnostic purposes.

Detection of salmonid alphavirus RNA in Celtic and Irish Sea flatfish

Pancreas disease (PD) caused by the salmonid alphavirus (SAV) has been the most significant cause of mortalities in Irish farmed salmon Salmo salar L. over the past decade. SAV is a single-strand positive-sense RNA virus, originally thought to be unique to salmonids, but has recently been detected using real-time RT-PCR in a number of wild non-salmonid fish. In the present report, 610 wild flatfish (common dab Limanda limanda, plaice Pleuronectes platessa and megrim Lepidorhombus whiffiagonis) were caught from the Irish and Celtic Seas and screened for SAV using real-time RT-PCR and sequencing. In general, a very low prevalence was recorded in common dab and plaice, except for 1 haul in Dublin Bay where 25% of common dab were SAV-positive. SAV sequence analysis supported the fact that real-time RT-PCR detections were specific and further characterised the detected viruses within SAV Subtype I, the predominant subtype found in farmed salmon in Ireland.

Geographical distribution of salmonid alphavirus subtypes in marine farmed Atlantic salmon, Salmo salar L., in Scotland and Ireland

Sequence data from salmonid alphavirus (SAV) strains obtained from farmed marine Atlantic salmon, Salmo salar L. , over a 20-year period between 1991 and 2011 was reviewed to examine the geographical distribution of the genetically defined SAV subtypes in twelve regions across Ireland and Scotland. Of 160 different Atlantic salmon SAV strains examined, 62 belonged to subtype 1, 28 to subtype 2, 34 to subtype 4, 35 to subtype 5 and 1 to subtype 6. SAV subtypes 1, 4 and 6 were found in Ireland, while subtypes 1, 2, 4 and 5 were found in Scotland. In the majority of regions, there was a clear clustering of subtypes, with SAV subtype 1 being the dominant subtype in Ireland overall, as well as in Argyll and Bute in Scotland. SAV subtype 2 predominated in the Shetland and Orkney Islands. The emergence in Atlantic salmon of subtype 2 strains typically associated with sleeping disease in rainbow trout in Argyll and Bute, strongly suggesting transmission of infection between these species, was noted for the first time. SAV subtype 4 was the most common subtype found in the southern Western Isles, while SAV subtype 5 predominated in the northern Western Isles and north-west mainland Scotland. No single strain was dominant on sites in the western Highlands, with a number of sites in this region in particular having more than one subtype detected in different submissions. The significance of these results in relation to aspects of the epidemiology of infection, including transmission, biosecurity and wildlife reservoirs are discussed and knowledge gaps identified.

Natural infection of vertebrate hosts by different lineages of Buggy Creek virus (family Togaviridae, genus Alphavirus)

Buggy Creek virus (BCRV; family Togaviridae, genus Alphavirus) is an arbovirus transmitted by the ectoparasitic swallow bug (Hemiptera: Cimicidae: Oeciacus vicarius) to cliff swallows (Petrochelidon pyrrhonota) and house sparrows (Passer domesticus). BCRV occurs in two lineages (A and B) that are sympatric in bird nesting colonies in the central Great Plains, USA. Previous work on lineages isolated exclusively from swallow bugs suggested that lineage A relies on amplification by avian hosts, in contrast to lineage B, which is maintained mostly among bugs. We report the first data on the BCRV lineages isolated from vertebrate hosts under natural conditions. Lineage A was overrepresented among isolates from nestling house sparrows, relative to the proportions of the two lineages found in unfed bug vectors at the same site at the start of the summer transmission season. Haplotype diversity of each lineage was higher in bugs than in sparrows, indicating reduced genetic diversity of virus amplified in the vertebrate host. BCRV appears to have diverged into two lineages based on different modes of transmission.

Studies on the possibility of vertical transmission of Norwegian salmonid Alphavirus in production of Atlantic salmon in Norway

Disease associated with salmonid Alphavirus (SAV) infection is a significant problem for farm production of salmonids in Europe. The SAV subtype 3 (SAV3) is a Norwegian subtype present exclusively in production systems for Atlantic salmon Salmo salar and rainbow trout Oncorhynchus mykiss in western Norway. It has been suggested that SAV3 is transmitted through smolt transport from the main area for SAV disease in western Norway to as far as northern Norway. One explanation for this type of spread is that SAV is present at freshwater production sites for Atlantic salmon smolts. The present study confirms this, showing that SAV3 is present at smolt production sites in Norway. At two sites in northern Norway that had received eggs from broodfish companies in Hordaland County, western Norway, 2-4-g fry were positive for SAV3. Hence, it cannot be excluded that vertical transmission could have contributed to the presence of SAV3 in northern Norway. In the present study, we followed the normal production cycle for Atlantic salmon in a fish farming company in Hordaland County. Twelve of 353 broodfish in study 1 and 28 of 31 broodfish in study 2 were found to be carriers of SAV3. In the same two studies, SAV was also detected in eggs (1 of 220), eyed eggs (3 of 270), and fry (6 of 600). The SAV was not detected in parr, smolts, or postsmolts, but after a year at sea the fish developed SAV disease. Given the difficulties in tracing the virus through the production cycle until development of SAV disease in the marine farm, we cannot draw any firm conclusions about whether vertical transmission occurs in Norwegian salmon production, and we cannot exclude the possibility that the development of SAV after 1 year at sea was caused by horizontal transmission rather than vertical transmission.

[Isolation and identification of arboviruses from mosquito pools in some regions of Liaoning province, China]

OBJECTIVE

To isolate and identify arboviruses from mosquito pools in some regions of Liaoning province.

METHODS

Mosquitoes were collected from Shenyang, Yingkou, Panjin, Jinzhou and Dandong cities of Liaoning province in 2006. Viruses were isolated by inoculating the specimens onto C6/ 36 and BHK-21cells. The new isolates were identified using serological and molecular biological methods.

RESULTS

5410 mosquitoes were collected from the five cities in total. Three isolates produced CPE in C6/ 36 cell and five isolates produced CPE in both C6/36 and BHK-21 cell. Three isolates (LN0684, LN0688 and LN0689) were identified as Banna virus and one isolate (LN0636) was identified as Getah virus. Phylogenetic analysis showed that the three Banna virus strains were clustered into the same evolution branch as the other Chinese isolates. The identity of nucleotide sequence was between 91.2% and 94.7%, compared with other Banna virus strains. The new isolated Getah virus was clustered into the same branch with the strain of South Korea (swine). The identity of nucleotide sequence was 99.2%, when comparing with the strain of South Korea and was 95% to 99% with the strains from Russia, mainland of China and Taiwan region. Conclusion Eight virus isolates, including three Banna virus, one Getah virus and four unknown virus strains were isolated from mosquitoes in Liaoning province. Banna virus and Getah virus were reported for the first time in Liaoning province, while Getah virus showed the highest nucleotide homology with the South Korea strains.

Phylogenetic analyses and molecular epidemiology of European salmonid alphaviruses (SAV) based on partial E2 and nsP3 gene nucleotide sequences

Sequence data were generated for portions of the E2 and nsP3 genes of 48 salmonid alphaviruses from farmed Atlantic salmon (AS), Salmo salar L., and rainbow trout (RT), Oncorhynchus mykiss (Walbaum), in marine and freshwater environments, respectively, from the Republic of Ireland, Northern Ireland, England, Scotland, Norway, France, Italy and Spain between 1991 and 2007. Based on these sequences, and those of six previously published reference strains, phylogenetic trees were constructed using the parsimony method. Trees generated with both gene segments were similar. Clades corresponding to the three previously recognized subtypes were generated and in addition, two further new clades of viruses were identified. A single further strain (F96-1045) was found to be distinct from all of the other strains in the study. The percentage of nucleotide divergence within clades was generally low (0-4.8% for E2, 0-6.6% for nsP3). Interclade divergence tended to be higher (3.4-19.7% for E2, 6.5-28.1% for nsP3). Based on these results and using current SAV terminology, the two new clades and F96-1045 were termed SAV subtypes 4, 5 and 6, respectively. SAV4 contained AS strains from Ireland and Scotland, while SAV5 contained only Scottish AS strains. Recently identified SAV strains from RT in Italy and Spain were shown to belong to SAV2. In addition, marine AS strains belonging to SAV2 were identified for the first time. Analysis of the origin of several clusters of strains with identical E2 and nsP3 sequences strongly support horizontal transmission of virus between farms and aquaculture companies. Evidence in support of vertical transmission was not found.

[Analysis of the genome of two Getah virus strains (LEIV 16275 Mar and LEIV 17741 MPR) isolated from mosquitoes in the North-Eastern Asia]

The complete nucleotide consequences of two Getah virus strains isolated in Russia (LEIV 16275 Mar) and Mongolia (LEIV 17741 MPR) were first determined and analyzed. The nucleotide sequences of the gene of surface glycoprotein E2 and complete genome were used to establish the phylogenetic relations of the strains with other representatives of the Semliki forest serocomplex. The study and reference strains of Getah virus were shown to form its own cluster that was far away from other representatives of the complex and the sequence of the E2 gene significantly reflected the identification of phylogenetical groups within the Sempliki forest serocomplex.

Direct broad-range detection of alphaviruses in mosquito extracts

Members of the genus Alphavirus are a diverse group of principally mosquito-borne RNA viruses. There are at least 29 species and many more subtypes of alphaviruses and some are considered potential bioweapons. We have developed a multi-locus RT-PCR followed by electrospray ionization mass spectrometry (RT-PCR/ESI-MS) assay that uses the amplicon base compositions to detect and identify alphaviruses. A small set of primer pairs targeting conserved sites in the alphavirus RNA genome were used to amplify a panel of 36 virus isolates representing characterized Old World and New World alphaviruses. Base compositions from the resulting amplicons could be used to unambiguously determine the species or subtype of 35 of the 36 isolates. The assay detected, without culture, Venezuelan equine encephalitis virus (VEEV), Eastern equine encephalitis virus (EEEV), and mixtures of both in pools consisting of laboratory-infected and -uninfected mosquitoes. Further, the assay was used to detect alphaviruses in naturally occurring mosquito vectors collected from locations in South America and Asia. Mosquito pools collected near Iquitos, Peru, were found to contain an alphavirus with a very distinct signature. Subsequent sequence analysis confirmed that the virus was a member of the Mucambo virus species (subtype IIID in the VEEV complex). The assay we have developed provides a rapid, accurate, and high-throughput assay for surveillance of alphaviruses.

[Molecular analysis on the capsid gene and 3' untranslation region of three Getah viruses isolated in China]

To compare the molecular characteristics of the Capsid gene and 3' untranslation region (3'UTR) of Getah viruses (GETV) isolated in Hainan Province and Hebei Province of China,the viral RNAs were extracted from M1(Hainan), HB0215-3 and HB0234(Hebei) virus stocks. Capsid gene segments and 3' UTR segments from three strains of Chinese GETV were obtained by RT-PCR and then sequenced. The obtained nucleotide sequences were analyzed using the Clustal X(1.8), DNASTAR, MAGA3.1 programs. The full-length Capsid gene of the 3 strains of Chinese GETV were comprised of 801, 804 and 804 nucleotides each, encoding the protein of 267,268 and 268 amino acids each. Sequencing of Capsid gene fragments showed that two strains of Hebei isolates were identical and had homology of 97.6% at nucleotide level and 97.8% at amino acids level with M1. Their homologies when compared with strains isolated from other countries were also high at nucleotide levels (95.4%-99.6%). The 3'UTR from the three strains were comprised of 411, 401 and 401 nucleotides each, and had found specific deletion of 10 nt at position 44-54 and two specific nucleotide sites that was T at position 64 and C at position 148. GETV isolated in China presented relation of the year of virus isolation with the phylogenesis distance when compared with the other GETV strains and comprised a genetically highly conserved group.

Tissue tropism of salmonid alphaviruses (subtypes SAV1 and SAV3) in experimentally challenged Atlantic salmon (Salmo salar L.)

Diagnosis of SAV infections has traditionally been based upon clinical observations together with a set of histopathological findings in exocrine pancreas, heart and skeletal muscle, but recently, real-time RT-PCR assays have been developed as a supplement for the detection of SAV. The aim of this study was to determine tissue tropism of SAV1 and SAV3 in Atlantic salmon Salmo salar L. in order to identify the most suitable tissues for real-time RT-PCR diagnostic assays. The results indicated that the pseudobranch and the heart (ventricle) are the most useful tissues for such assays, regardless of disease status. The pyloric caecae with associated pancreatic tissue is unsuitable for diagnosis using this method. The use of real-time RT-PCR enabled viral RNA detection at all stages of the disease, including in surviving fish six months after infection. Considering the short production cycle of farmed salmonids, this suggests that surviving Atlantic salmon may become life-long asymptomatic carriers of SAV after an infection.

Genomic analysis of a Chinese isolate of Getah-like virus and its phylogenetic relationship with other Alphaviruses

An alphavirus, M-1 strain, was isolated from a pool of culicine mosquitoes collected in Hainan island of China during an arbovirus survey in 1964. In the present study, we determined the complete nucleotide sequence of the M-1 strain using RT-PCR and RACE techniques. The M-1 genome is 11,690 nucleotides (nt) in length and contains two open reading frames (ORFs) encoding four nonstructural proteins and five structural proteins, respectively. Searches using Blast and comparison analyses suggested that M-1 is closely linked to Sagiyama virus (SAGV, AB032553) with 98% identity and Getah viruse (GETV, AY702913) with 97.8% identity in the full-length nucleotide sequence. However, compared with SAGV, there is 1 deletion (3 nucleotides in length) in the Capsid region, a deletion in the 3' untranslated region (10 nucleotides in length) and 2 insertions in the 3' untranslated region involving a total of 5 nucleotides. Interestingly, from the 5' UTR to the end of coding region, M-1 share the highest identity with GETV, even though the identity of 3' UTR drops dramatically to 76.2%. Furthermore, phylogenetic analysis based on the complete genomic sequences and sequences for structural or non-structural proteins of M-1 and 15 alphaviruses showed that M-1 grouped with GETV first and then grouped together with SAGV. Based on the comparison analysis and phylogenetic analysis, we conclude that M-1 strain can be considered as a strain that is a Chinese isolate of Getah-like virus.

The Old World and New World alphaviruses use different virus-specific proteins for induction of transcriptional shutoff

Alphaviruses are widely distributed throughout the world. During the last few thousand years, the New World viruses, including Venezuelan equine encephalitis virus (VEEV) and eastern equine encephalitis virus (EEEV), evolved separately from those of the Old World, i.e., Sindbis virus (SINV) and Semliki Forest virus (SFV). Nevertheless, the results of our study indicate that both groups have developed the same characteristic: their replication efficiently interferes with cellular transcription and the cell response to virus replication. Transcriptional shutoff caused by at least two of the Old World alphaviruses, SINV and SFV, which belong to different serological complexes, depends on nsP2, but not on the capsid protein, functioning. Our data suggest that the New World alphaviruses VEEV and EEEV developed an alternative mechanism of transcription inhibition that is mainly determined by their capsid protein, but not by the nsP2. The ability of the VEEV capsid to inhibit cellular transcription appears to be controlled by the amino-terminal fragment of the protein, but not by its protease activity or by the positively charged RNA-binding domain. These data provide new insights into alphavirus evolution and present a plausible explanation for the particular recombination events that led to the formation of western equine encephalitis virus (WEEV) from SINV- and EEEV-like ancestors. The recombination allowed WEEV to acquire capsid protein functioning in transcription inhibition from EEEV-like virus. Identification of the new functions in the New World alphavirus-derived capsids opens an opportunity for developing new, safer alphavirus-based gene expression systems and designing new types of attenuated vaccine strains of VEEV and EEEV.

Phylogenetic analysis of Buggy Creek virus: evidence for multiple clades in the Western Great Plains, United States of America

We present the first detailed phylogenetic analysis of Buggy Creek virus (BCRV), a poorly known alphavirus with transmission cycles involving a cimicid swallow bug (Oeciacus vicarius) vector and cliff swallows (Petrochelidon pyrrhonota) and house sparrows (Passer domesticus) as the principal avian hosts. Nucleotide sequences of a 2,075-bp viral envelope glycoprotein-coding region, covering the entire PE2 gene, were determined for 33 BCRV isolates taken from swallow bugs at cliff swallow colonies in Nebraska and Colorado in the summer of 2001 and were compared with the corresponding region of BCRV isolates collected from Oklahoma in the 1980s. We also analyzed isolates of the closely related Fort Morgan virus (FMV) collected from Colorado in the 1970s. Phylogenetic analysis indicated that BCRV falls into the western equine encephalomyelitis complex of alphaviruses, in agreement with antigenic results and a previous alphavirus phylogeny based on the E1 coding region. We found four distinct BCRV/FMV clades, one each unique to Nebraska, Colorado, and Oklahoma and one containing isolates from both Nebraska and Colorado. BCRV isolates within the two clades from Nebraska showed 5.7 to 6.2% nucleotide divergence and 0.7 to 1.9% amino acid divergence, and within these clades, we found multiple subclades. Nebraska subclades tended to be confined to one or a few cliff swallow colonies that were close to each other in space, although in some cases, near-identical isolates were detected at sites up to 123 km apart. Viral gene flow occurs when cliff swallows move (bugs) between colony sites, and the genetic structure of BCRV may reflect the limited dispersal abilities of its insect vector.

O'nyong-nyong Virus, Chad

We report the first laboratory-confirmed human infection with O'nyong-nyong virus in Chad. This virus was isolated from peripheral blood mononuclear cells of a patient with evidence of a seroconversion to a virus related to Chikungunya virus. Genome sequence was partly determined, and phylogenetic studies were conducted.

Mayaro virus: complete nucleotide sequence and phylogenetic relationships with other alphaviruses

Mayaro (MAY) virus is a member of the genus Alphavirus in the family Togaviridae. Alphaviruses are distributed throughout the world and cause a wide range of diseases in humans and animals. Here, we determined the complete nucleotide sequence of MAY from a viral strain isolated from a French Guianese patient. The deduced MAY genome was 11,429 nucleotides in length, excluding the 5' cap nucleotide and 3' poly(A) tail. Nucleotide and amino acid homologies, as well as phylogenetic analyses of the obtained sequence confirmed that MAY is not a recombinant virus and belongs to the Semliki Forest complex according to the antigenic complex classification. Furthermore, analyses based on the E1 region revealed that MAY is closely related to Una virus, the only other South American virus clustering with the Old World viruses. On the basis of our results and of the alphaviruses diversity and pathogenicity, we suggest that alphaviruses may have an Old World origin.

Genetic stability within the Norwegian subtype of salmonid alphavirus (family Togaviridae)

Salmonid alphavirus (SAV) (family Togaviridae) causes mortality in Atlantic salmon (Salmo salar L.) and rainbow trout (Oncorhynchus mykiss W.) in Norway, France, UK, and Ireland. At least three subtypes of SAV exist: SPDV in UK/Ireland, SDV in France/UK, and the recently reported Norwegian salmonid alphavirus (NSAV) in western Norway. During 2003 and 2004, disease caused by NSAV was reported for the first time in northern Norway, more than 800 km away from the enzootic area in western Norway. The present study has investigated the phylogenetic relationships among 20 NSAV isolates, based on a 1221-nt-long segment covering part of the capsid gene, E3, and part of the E2 gene, collected over a period of eight years. The results revealed genetic homogeneity among NSAV isolates, including those from northern Norway. The SDV or SPDV subtypes were not found in diseased Norwegian fish. A substitution rate of 1.70 (+/-1.03) x 10(-4) nt subst/site/year was obtained for the NSAV subtype by maximum likelihood analysis. The second aim of this study was to clarify whether NSAV changes genotypically in cell culture by culturing a NSAV isolate through 20 passages in CHSE-214 cells. Sequencing of almost the entire genome (11530 nt) after 20 passages revealed four nucleotide substitutions, all resulting in amino acid substitutions. One of these substitutions, serine to proline in E2 position 206, was also found to have occurred in field isolates.

Sensitive and specific detection of Salmonid alphavirus using real-time PCR (TaqMan)

Pancreas disease is responsible for major economic losses in the European salmonid farming industry. It was previously believed that a single subtype (salmon pancreas disease virus) of the virus species Salmonid alphavirus (SAV) was responsible for all outbreaks of pancreas disease in the UK and Norway. However, the recent discovery that pancreas disease in Norway is caused by a new and distinct subtype of salmonid alphavirus, exclusively found in Norway, has advocated the need for better diagnostic tools. In the present paper, three real-time PCR assays for all known subtypes of salmonid alphavirus have been developed; the Q_nsP1 assay is a broad-spectrum one that detects RNA from all subtypes, the Q_SPDV assay specifically detects the salmon pancreas disease virus subtype, and the Q_NSAV assay only detects the new Norwegian salmonid alphavirus subtype. The results demonstrated the assays to be highly sensitive and specific, detecting <0.1TCID50 of virus stocks. Regression analysis and standard curves calculated from the Ct-values from 10-fold serial dilutions of virus stocks showed that the assays were highly reproducible over a wide range of RNA input. Thirty-nine field samples were tested in triplicate and compared with traditional RT-PCR. Overall, the real-time assays detected 35 positive compared to 29 positives in standard RT-PCR, and were thus shown to be more sensitive for detecting salmonid alphaviruses in field samples.

Simultaneous identification of orthopoxviruses and alphaviruses by oligonucleotide macroarray with special emphasis on detection of variola and Venezuelan equine encephalitis viruses

The development of a method in macroarray format for the identification of alphaviruses and orthopoxviruses in samples of concern in biodefense is reported. Capture oligonucleotides designed to bind generic members of the orthopox- or alphavirus families and a collection of additional oligonucleotides to bind specifically nucleic acids from five individual alphaviruses, including Venezuelan equine encephalitis, or DNA from each of four orthopoxviruses, including variola virus (VAR) were deposited onto nylon membranes. Hybridization of digoxigenin labeled PCR products to the macroarray produced results easily observable to the naked eye. Multiplex RT-PCR utilizing both orthopox- and alphavirus-generic primers yielded amplification of DNA corresponding to the expected sizes of the orthopoxvirus and alphavirus fragments, respectively. Hybridization of samples to capture oligonucleotides in the macroarray membranes identified correctly generic orthopox- or alphaviral sequences. The hybridizations correctly identified each of the three alphaviruses and two orthopoxviruses tested. We observed cross-hybridization only once (between two alphaviruses) that was less intense than the spots formed by correct hybridization. The macroarray test described below is easy to perform, inexpensive, relatively fast, uncomplicated to interpret, and its end point is read visually without the need of additional equipment. This nucleic acid hybridization assay onto nylon membranes in macroarray format can help in detecting or excluding the presence of threat viruses in environmental samples and appears promising for a variety of biodefense applications.

Duplex reverse transcription-PCR followed by nested PCR assays for detection and identification of Brazilian alphaviruses and flaviviruses

A new approach was developed for the rapid detection and identification of Brazilian alphaviruses and flaviviruses. The methodology involves the genus-specific detection of Alphavirus and Flavivirus by a duplex reverse transcription-PCR (D-RT-PCR), followed by multiplex nested PCR (M-N-PCR) or nested PCR (N-PCR) assays for species-specific identification. By this protocol, 25 arboviruses were specifically detected and identified. Detection levels between 10(1.3) and 10(3.5) 50% tissue culture infective doses (TCID(50))/ml of Flavivirus and Alphavirus strains were achieved by D-RT-PCR, and levels of <1 TCID(50)/ml were achieved by M-N-PCR assays. To assess the suitability and clinical application of this methodology, a total of 101 human or animal stored samples were analyzed. Results obtained suggest that this technique could be applied as a rapid diagnostic tool in clinical samples in which arbovirus infection is suspected and differential diagnosis is required, avoiding the need to test specimens by separate PCR methods.

Differential infectivities of o'nyong-nyong and chikungunya virus isolates in Anopheles gambiae and Aedes aegypti mosquitoes

O'nyong-nyong virus (ONNV) and chikungunya virus (CHIKV) are closely related alphaviruses that cause human disease in Africa and Asia. Like most alphaviruses, CHIKV is vectored by culicine mosquitoes. ONNV is considered unusual as it primarily infects anopheline mosquitoes; however, there are relatively few experimental data to support this. In this study, three strains of ONNV and one strain of CHIKV were evaluated in Anopheles gambiae and Aedes aegypti mosquitoes and in four cell lines. As predicted, CHIKV was not infectious to An. gambiae, and we observed strain-variability for ONNV with respect to the ability of the virus to infect An. gambiae and Ae. aegypti. The species specificity in vivo was reflected by in vitro experiments using culicine and anopheline-derived cell lines.

Antigenic and genetic typing of Whataroa viruses in Australia

We recently characterized three novel alphaviruses isolated from mosquitoes captured in New South Wales, Australia. Initial cross-neutralization studies revealed antigenic similarity to the Sindbis virus (SINV)-like Whataroa virus (WHAV), heretofore found only in New Zealand. Nucleotide sequence analysis showed that the WHAV-like viruses shared >99% nucleotide sequence similarity with each other, and 96-97% similarity with prototype WHAV. Enzyme-linked immunosorbent assay reactions of a panel of monoclonal antibodies to SINV showed that the novel WHAV-like viruses displayed identical binding patterns and were antigenically distinct from all SINV isolates examined. Although these viruses displayed a similar binding pattern to prototype WHAV, three monoclonal antibodies discriminated them from the New Zealand virus. Our results suggest that these novel alphaviruses are antigenic variants of WHAV and represent the first reported isolations of this virus from outside New Zealand. The monoclonal antibodies used in this study will be useful for typing new SINV and SINV-like isolates.

Expression of the zinc-finger antiviral protein inhibits alphavirus replication

The rat zinc-finger antiviral protein (ZAP) was recently identified as a host protein conferring resistance to retroviral infection. We analyzed ZAP's ability to inhibit viruses from other families and found that ZAP potently inhibits the replication of multiple members of the Alphavirus genus within the Togaviridae, including Sindbis virus, Semliki Forest virus, Ross River virus, and Venezuelan equine encephalitis virus. However, expression of ZAP did not induce a broad-spectrum antiviral state as some viruses, including vesicular stomatitis virus, poliovirus, yellow fever virus, and herpes simplex virus type 1, replicated to normal levels in ZAP-expressing cells. We determined that ZAP expression inhibits Sindbis virus replication after virus penetration and entry, but before the amplification of newly synthesized plus strand genomic RNA. Using a temperature-sensitive Sindbis virus mutant expressing luciferase, we further showed that translation of incoming viral RNA is blocked by ZAP expression. Elucidation of the antiviral mechanism by which ZAP inhibits Sindbis virus translation may lead to the development of agents with broad activity against alphaviruses.

Viruses of the Bunya- and Togaviridae families: potential as bioterrorism agents and means of control

When considering viruses of potential importance as tools for bioterrorism, several viruses in the Bunya- and Togaviridae families have been cited. Among those in the Bunyaviridae family are Rift Valley fever, Crimean-Congo hemorrhagic fever, hanta, and sandfly fever viruses, listed in order of priority. Those particularly considered in the Togaviridae family are Venezuelan, eastern and western equine encephalitis viruses. Factors affecting the selection of these viruses are the ability for them to induce a fatal or seriously incapacitating illness, their ease of cultivation in order to prepare large volumes, their relative infectivity in human patients, their ability to be transmitted by aerosol, and the lack of measures available for their control. Each factor is fully considered in this review. Vaccines for the control of infections induced by these viruses are in varying stages of development, with none universally accepted to date. Viruses in the Bunyaviridae family are generally sensitive to ribavirin, which has been recommended as an emergency therapy for infections by viruses in this family although has not yet been FDA-approved. Interferon and interferon inducers also significantly inhibit these virus infections in animal models. Against infections induced by viruses in the Togaviridae family, interferon-alpha would appear to currently be the most useful for therapy.

Evolutionary relationships and systematics of the alphaviruses

Partial E1 envelope glycoprotein gene sequences and complete structural polyprotein sequences were used to compare divergence and construct phylogenetic trees for the genus Alphavirus. Tree topologies indicated that the mosquito-borne alphaviruses could have arisen in either the Old or the New World, with at least two transoceanic introductions to account for their current distribution. The time frame for alphavirus diversification could not be estimated because maximum-likelihood analyses indicated that the nucleotide substitution rate varies considerably across sites within the genome. While most trees showed evolutionary relationships consistent with current antigenic complexes and species, several changes to the current classification are proposed. The recently identified fish alphaviruses salmon pancreas disease virus and sleeping disease virus appear to be variants or subtypes of a new alphavirus species. Southern elephant seal virus is also a new alphavirus distantly related to all of the others analyzed. Tonate virus and Venezuelan equine encephalitis virus strain 78V3531 also appear to be distinct alphavirus species based on genetic, antigenic, and ecological criteria. Trocara virus, isolated from mosquitoes in Brazil and Peru, also represents a new species and probably a new alphavirus complex.

A generic nested-RT-PCR followed by sequencing for detection and identification of members of the alphavirus genus

A specific and sensitive nested RT-PCR method was developed for the detection of members of the alphavirus genus. Based on available sequences, degenerated primers were selected in the nsP4 gene. Reaction components and thermal cycling parameters were investigated and standardised, and optimal ones were selected. As few as 25 pfu/tube could be detected. The identities of the amplified fragments were confirmed by sequencing, and phylogenetic analysis was carried out. The resulting phylogenetic tree could be applied to classify every alphavirus according to its serogroup. This technique is suitable for rapid, sensitive and reliable detection of these viruses and may be very valuable for diagnostic applications and surveillance.

[Two virus strains of isolated in China are recombinant alphaviruses]

OBJECTIVE

To determine the classification, phylogenetic and genetic type of XJ-90260 and XJ-91006 viruses isolated in China.

METHODS

Two pairs of specific primers were designed to amplify the NSP4 and E1-3' UTR genes of XJ-90260 and XJ-91006 viruses and the nucleotide sequences between them and with that of other Alphavirus were compared.

RESULTS

The nucleotide sequences identity between XJ-90260 and XJ-91006 viruses was 100% and has showed the highest with WEE, comparing with the other 26 Alphaviruses in 3'-UTR. NSP4 gene of XJ-90260 and XJ-91006 viruses high homologous with EEE virus and E-1 gene high homologous wih SIN virus. XJ-90260 and XJ-91006 viruses belong to the B group of WEE and are closest to the Russian strain (Y62-33) by phylogenetic analysis.

CONCLUSION

XJ-90260 and XJ-91006 viruses isolated in China are recombinant Alphaviruses, they belong to the same genetic type as WEE does.

Arbovirus of marine mammals: a new alphavirus isolated from the elephant seal louse, Lepidophthirus macrorhini

A novel alphavirus was isolated from the louse Lepidophthirus macrorhini, collected from southern elephant seals, Mirounga leonina, on Macquarie Island, Australia. The virus displayed classic alphavirus ultrastructure and appeared to be serologically different from known Australasian alphaviruses. Nearly all Macquarie Island elephant seals tested had neutralizing antibodies against the virus, but no virus-associated pathology has been identified. Antarctic Division personnel who have worked extensively with elephant seals showed no serological evidence of exposure to the virus. Sequence analysis illustrated that the southern elephant seal (SES) virus segregates with the Semliki Forest group of Australasian alphaviruses. Phylogenetic analysis of known alphaviruses suggests that alphaviruses might be grouped according to their enzootic vertebrate host class. The SES virus represents the first arbovirus of marine mammals and illustrates that alphaviruses can inhabit Antarctica and that alphaviruses can be transmitted by lice.