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As COVID-19 has shown, pandemics and outbreaks of emerging infections such as Zika, Nipah, monkeypox and antimicrobial-resistant pathogens, especially emerging zoonotic diseases, continue to occur and may even be increasing in Southeast Asia. In addition, these infections often result from environmental changes and human behaviour. Overall, public health surveillance to identify gaps in the literature and early warning signs are essential in this region. A systematic review investigated the prevalence of emerging zoonotic diseases over 11 years from 2011 to 2022 in Southeast Asia to understand the status of emerging zoonotic diseases, as well as to provide necessary actions for disease control and prevention in the region. During the 2011-2022 period, studies on pigs, poultry, ruminants, companion animals and wildlife in Southeast Asia were reviewed thoroughly to assess the quality of reporting items for inclusion in the systematic review. The review was performed on 26 studies of pigs, 6 studies of poultry, 21 studies of ruminants, 28 studies of companion animals and 25 studies of wildlife in Southeast Asia, which provide a snapshot of the prevalence of the emerging zoonotic disease across the country. The findings from the review showed that emerging zoonotic diseases were prevalent across the region and identified a few zoonotic diseases associated with poultry, mainly stemming from Cambodia and Vietnam, as high priority in Southeast Asia. Clinical relevance : Appropriate prevention and control measures should be taken to mitigate the emerging zoonotic diseases in Southeast Asia.

Japanese encephalitis (JE) is the major cause of viral encephalitis (VE) in most Asian-Pacific countries. In Vietnam, there is no nationwide surveillance system for JE due to lack of medical facilities and diagnoses. Culex tritaeniorhynchus, Culex vishnui, and Culex quinquefasciatus have been identified as the major JE vectors in Vietnam. The main objective of this study was to forecast a risk map of Culex mosquitoes in Hanoi, which is one of the most densely populated cities in Vietnam. A total of 10,775 female adult Culex mosquitoes were collected from 513 trapping locations. We collected temperature and precipitation information during the study period and its preceding month. In addition, the other predictor variables (e.g., normalized difference vegetation index [NDVI], land use/land cover and human population density), were collected for our analysis. The final model selected for estimating the Culex mosquito abundance included centered rainfall, quadratic term rainfall, rice cover ratio, forest cover ratio, and human population density variables. The estimated spatial distribution of Culex mosquito abundance ranged from 0 to more than 150 mosquitoes per 900m2. Our model estimated that 87% of the Hanoi area had an abundance of mosquitoes from 0 to 50, whereas approximately 1.2% of the area showed more than 100 mosquitoes, which was mostly in the rural/peri-urban districts. Our findings provide better insight into understanding the spatial distribution of Culex mosquitoes and its associated environmental risk factors. Such information can assist local clinicians and public health policymakers to identify potential areas of risk for JE virus. Risk maps can be an efficient way of raising public awareness about the virus and further preventive measures need to be considered in order to prevent outbreaks and onwards transmission of JE virus., Competing Interests: The authors have declared that no competing interests exist.

Livestock production has increased in many emerging economies, but productivity is often substantially impaired by infectious diseases. The first step towards improved livestock health and productivity is to map the presence of livestock diseases. The objective of this review was to summarize studies conducted on such diseases in an emerging economy, Vietnam, and thereby identifying knowledge gaps that may inform the design of surveillance and control programs. Few studies were found to evaluate the distribution of infectious livestock diseases other than avian influenza. Also, many regions with dense livestock populations had received little attention in terms of disease investigation. A large proportion of the studies dealt with zoonoses and food-borne infections which might be due to funding agencies priorities. On the contrary, studies targeting infections that affect livestock and their productivity were few. We think that this limitation in scientific reports on infectious diseases that only affect livestock productivity is a common phenomenon in low and lower middle income countries. More science-based data on such diseases would help policymakers to prioritize which livestock diseases should be subject to animal health programs aimed to support rural livelihoods and economic development.

The main objectives of this study were to model various scenarios of African swine fever (ASF) virus transmission among farms in Vietnam and to evaluate the impact of control strategies using North American Animal Disease Spread Model (NAADSM). A total of 7,882 pig farms in the Red River Delta (RRD) region were obtained from the General Statistics Office, and then, random points corresponding to the number of farms in each province were generated as exact farm locations were not available. A total of 10 models were developed, including movement control scenarios. In addition, we conducted sensitivity analysis to assess the impact of indirect contact transmission probability (TP). Overall, the indirect contact exhibited an important role in transmitting the ASF virus. In order to minimize ASF transmission between farms, we found that movement restriction needed to reach a certain level (approximately between 50% and 75%) and that the restriction had to be applied in a timely manner. This study offers valuable insight into how ASF virus can be transmitted via direct and indirect contact and controlled among farms under the various simulation scenarios. Our results suggest that the enforcement of movement restriction was an effective control measure as soon as the outbreaks were reported. In addition, this study provided evidence that high standards of biosecurity can contribute to the reduction of disease spread., (© 2020 The Authors. Transboundary and Emerging Diseases published by Wiley-VCH GmbH.)

Diseases caused by flaviviruses, including dengue fever and Japanese encephalitis, are major health problems in Vietnam. This cross-sectional study explored the feasibility of domestic dogs as sentinels to better understand risks of mosquito-borne diseases in Hanoi city. A total of 475 dogs serum samples from 221 households in six districts of Hanoi were analyzed by a competitive enzyme-linked immunosorbent assay (cELISA) for antibodies to the pr-E protein of West Nile virus and other flaviviruses due to cross-reactivity. The overall flavivirus seroprevalence in the dog population was 70.7% (95% CI = 66.4-74.8%). At the animal level, significant associations between seropositive dogs and district location, age, breed and keeping practice were determined. At the household level, the major risk factors were rural and peri-urban locations, presence of pigs, coil burning and households without mosquito-borne disease experience ( p < 0.05). Mosquito control by using larvicides or electric traps could lower seropositivity, but other measures did not contribute to significant risk mitigation of flavivirus exposure in dogs. These results will support better control of mosquito-borne diseases in Hanoi, and they indicate that dogs can be used as sentinels for flavivirus exposure.

African swine fever virus is highly contagious, and mortality rates reach up to 100% depending on the host, virus dose, and the transmission routes. The main objective of this study was to develop a network-based simulation model for the farm-level transmission of ASF virus to evaluate the impact of changes in farm connectivity on ASF spread in Vietnam. A hypothetical population of 1,000 pig farms was created and used for the network-based simulation, where each farm represented a node, and the connection between farms represented an edge. The three scenarios modelled in this way (baseline, low, and high) evaluated the impact of connectivity on disease transmission. The median number of infected farms was higher as the connectivity increased (low: 659, baseline: 968 and high: 993). In addition, we evaluated the impact of the culling strategy on the number of infected farms. A total of four scenarios were simulated depending on the timing of culling after a farm was infected. We found that the timing of culling at 16, 12, 8, and 6 weeks had resulted in a reduction of the number of median infected farms by 81.92%, 91.63%, 100%, and 100%, respectively. Finally, our evaluation of the implication of stability of ties between farms indicated that if the farms were to have the same trading partners for at least six months could significantly reduce the median number of infected farms to two (95th percentile: 413) than in the basic model. Our study showed that pig movements among farms had a significant influence on the transmission dynamics of ASF virus. In addition, we found that the either timing of culling, reduction in the number of trading partners each farm had, or decreased mean contact rate during the outbreaks were essential to prevent or stop further outbreaks., Competing Interests: NO authors have competing interests Enter: The authors have declared that no competing interests exist.

Background: Hepatitis E virus (HEV) is a zoonotic disease and has been reported around the world. The main objective of this study was to evaluate the sero-prevalence and phylogenetic analysis of HEV in Vietnam. Pig blood and fecal pooled samples were collected to assess the prevalence of HEV. We assessed the true prevalence (TP) of HEV from apparent prevalence (AP) by taking into account the sensitivity and specificity of diagnostic tests using a Bayesian approach. For phylogenetic analysis, the data compared with worldwide HEV reference strains including all eight genotypes (G1-G8) which were identified in previous study., Results: A total of 475 sera and 250 fecal pooled samples were collected at slaughterhouses and pig farms from five provinces, in Viet Nam. Overall, the sero-AP of HEV was 58.53% (95% confidence interval: 53.95-62.70) while the sero-TP was slightly higher (65.43, 95% credible interval: 47.19-84.70). In terms of pooled samples, overall, the RNA-AP was 6.80% (95% confidence interval: 4.01-10.66). One strain in Hanoi, two strains in Dak Lak, seven strains in An Giang, four strains in Son La and two strains in Nghe An were isolated. The phylogenetic tree demonstrated that 19 Vietnamese strains were clustered into HEV 3 and 4., Conclusions: This study provided evidence that HEV is circulating in domestic pigs in Vietnam. From a public health perspective, it is very important to raise public awareness for high-risk groups (e.g. slaughterhouse workers, pig traders, farmers and market sellers) who have more opportunities to come in contact with pig and contaminated meats.

In Vietnam, Foot-and-mouth disease (FMD) is endemic, but no nationwide studies have been conducted to assess the monthly variations and space-time clusters of FMD. The main objective was to identify the temporal patterns and space-time clusters of FMD from 2007 to 2017 using national surveillance data in Vietnam. A total of 163,733 cases were reported from 2007 to 2017. Among them, the proportion of buffaloes (43.31% of total reported cases; 70,909 cases) was highest followed by cattle (30.11%; 49,306 cases), pigs (26.67%; 43,662 cases) and sheep/goats (0.41%; 675 cases). The serotype O was widely distributed across the country while serotype A was observed in Northeast, Central and Southern part of Vietnam while Asia 1 has been not identified since 2007. For monthly variations, most cases were observed during the dry season (from November to March) except Central Highlands. Under the spatial window was set at 50%, a total of seven clusters were identified. The primary cluster was observed from Dec 2009 to Dec 2010 in the northwest (radius: 101.67 km), showing a ratio of 3.75. The secondary cluster was detected in the northeast region (radius: 76.54 km) with a ratio of 3.53 in Feb 2017. The 3rd cluster was the largest with a radius of 176.69 km and located in the southern part of Vietnam. Interestingly, the most temporal clusters included between December and March during the study period. Our findings provide better insight into the temporal patterns and distribution of clusters of FMD in Vietnam. This study provides useful information to policymakers on the hotspot areas and timing of outbreaks. It also identifies when and where national surveillance and control programmes could be implemented more efficiently for the prevention and control of FMD., (© 2019 The Authors. Transboundary and Emerging Diseases published by Blackwell Verlag GmbH.)

Background: In Vietnam, lack of animal health information is considered a major challenge for pig production. The main objective of this study was to assess the seroprevalences of five pathogens [porcine circovirus type 2 (PCV2), porcine reproductive and respiratory syndrome virus (PRRSV), mycoplasma hyopneumoniae (M. hyo), Japanese encephalitis virus (JEV) and leptospirosis] and to better characterize the farm movements through a survey., Results: A total of 600 samples were collected from 120 farms from Bac Giang and Nghe An. Among unvaccinated herds, the highest seroprevalence was found for JE with 73.81% (95% CI: 68.39-78.74) in Bac Giang and 53.51% (95% CI 47.68-59.27) in Nghe An. Seroprevalences for PCV2 and M.hyo were 49.43% (95% CI: 45.06-53.80) and 46.06% (95% CI: 41.48-50.69) among unvaccinated animals. Accumulative co-infections for JE (86.25%) showed the highest level followed by M. hyo (66.25%) and PCV2 (62.50%). Three co-infections with JE had the highest positive rate (28.75%) followed by four co-infections (25.0%). Medium farms had relatively higher herd prevalences for all pathogens, except from leptospirosis. Overall, farmers exported/imported their pigs at the most 1-2 times every 6 months. Some respondents (5% for exportation and 20% for importation) had moved pigs more than 6 times over the last 6 months., Conclusions: Our study provided another pool of evidence that showed that PCV2, PRRS and H. hyo are endemic in pigs in Vietnam. Given the economic impacts of these pathogens elsewhere, the findings confirm the need for studies to evaluate the association between antibody response and clinical relevance as well as to assess the economic impact of co-infections at farm level. We also found that high seroprevalences of JE and leptospirosis were detected in pigs. From a pubic health point of view, it is crucial to raise public awareness especially for high risk occupations (mainly pig farm workers).

Background: Dengue fever is the most widespread infectious disease of humans transmitted by Aedes mosquitoes. It is the leading cause of hospitalization and death in children in the Southeast Asia and western Pacific regions. We analyzed surveillance records from health centers in Vietnam collected between 2001-2012 to determine seasonal trends, develop risk maps and an incidence forecasting model., Methods: The data were analyzed using a hierarchical spatial Bayesian model that approximates its posterior parameter distributions using the integrated Laplace approximation algorithm (INLA). Meteorological, altitude and land cover (LC) data were used as predictors. The data were grouped by province (n = 63) and month (n = 144) and divided into training (2001-2009) and validation (2010-2012) sets. Thirteen meteorological variables, 7 land cover data and altitude were considered as predictors. Only significant predictors were kept in the final multivariable model. Eleven dummy variables representing month were also fitted to account for seasonal effects. Spatial and temporal effects were accounted for using Besag-York-Mollie (BYM) and autoregressive (1) models. Their levels of significance were analyzed using deviance information criterion (DIC). The model was validated based on the Theil's coefficient which compared predicted and observed incidence estimated using the validation data. Dengue incidence predictions for 2010-2012 were also used to generate risk maps., Results: The mean monthly dengue incidence during the period was 6.94 cases (SD 14.49) per 100,000 people. Analyses on the temporal trends of the disease showed regular seasonal epidemics that were interrupted every 3 years (specifically in July 2004, July 2007 and September 2010) by major fluctuations in incidence. Monthly mean minimum temperature, rainfall, area under urban settlement/build-up areas and altitude were significant in the final model. Minimum temperature and rainfall had non-linear effects and lagging them by two months provided a better fitting model compared to using unlagged variables. Forecasts for the validation period closely mirrored the observed data and accurately captured the troughs and peaks of dengue incidence trajectories. A favorable Theil's coefficient of inequality of 0.22 was generated., Conclusions: The study identified temperature, rainfall, altitude and area under urban settlement as being significant predictors of dengue incidence. The statistical model fitted the data well based on Theil's coefficient of inequality, and risk maps generated from its predictions identified most of the high-risk provinces throughout the country., Competing Interests: The authors have declared that no competing interests exist.

The main objective of this study was to develop various models using North American Animal Disease Spread Model (NAADSM) to simulate the transmission of Porcine reproductive and respiratory syndrome (PRRS) virus between farms in Nghe An Province in Vietnam in order to inform the prevention and control of this important disease. Using real data from the household survey, credible parameters for direct/indirect mean contact rates between different farms were estimated. A total of eleven models were developed, including immunization scenarios. In addition, we conducted sensitive analysis on how the mean contact rates influenced the results. The immunization scenarios showed that a high proportion of pigs in medium size farms needs to be vaccinated in order to reduce the transmission to pigs in small farms under the Vietnamese pig production system. In order to promote the use of vaccinations, incentives (such as a vaccine subsidy) for medium size farms may be needed. It could be the most cost-effective control and prevention strategy for pig diseases in Vietnam. Our study provides insights on how pig diseases can be spread between pig farms via direct and indirect contact in Nghe An under the various hypothetical scenarios. Our results suggest that medium/large farms may play an important role in the transmission of pig diseases., (© 2019 The Authors Transboundary and Emerging Diseases Published by Blackwell Verlag GmbH.)

Background: Leptospirosis is an important zoonotic disease with a global distribution, affecting a wide range of mammalian animals and humans. Japanese encephalitis (JE) virus is the major vector-borne zoonotic disease in the Asia-Pacific region. The main objective of this study was to evaluate the seroprevalence of serovar-specific Leptospira and JE in swine from 10 provinces in Vietnam., Methods: Samples were initially collected for swine influenza surveillance from March to April 2017 at large-scale farms (with at least 50 sows and/or 250 fattening pigs) with pigs that tested positive for influenza in the previous surveillance period (2015-16)., Findings: A total of 2,000 sera samples were analyzed from 10 provinces. Overall, the seroprevalence of leptospirosis was 21.05% (95% CI: 19.28-22.90) using a cut-off titer of ≥ 1:100. The apparent prevalence of JE was 73.45% (95% CI: 71.46-75.37) while the true prevalence was slightly higher (74.46%, 95% credible interval: 73.73-86.41). We found a relatively high presence of leptospirosis and JE in pigs kept on large farms. Prevalence was comparable with other studies suggesting opportunistic testing of samples collected for other surveillance purposes can be a valuable tool to better understand and prevent the potential transmission of these zoonotic diseases from pigs to people in Vietnam., Conclusion: Our study provides evidence to veterinarians and animal health professionals for evidence-based practice such as diagnosis, vaccination and zoonotic control. Further investigation into the possible role of different domestic animals, wildlife species or environmental factors is needed to identify the potential risk factors and transmission routes in Vietnam., Competing Interests: The authors have declared that no competing interests exist.

Five new sesterterpenes, 14,15-dehydro-6- epi -ophiobolin K ( 1 ), 14,15-dehydro- ophiobolin K ( 2 ), 14,15-dehydro-6- epi -ophiobolin G ( 3 ), 14,15-dehydro-ophiobolin G ( 4 ) and 14,15-dehydro-( Z )-14-ophiobolin G ( 5 ), together with four known ophiobolins ( 6 - 9 ) were isolated from the marine fungus Aspergillus flocculosus derived from the seaweed Padina sp. collected in Vietnam. The five new ophiobolins were first isolated as ophiobolin derivatives consisting of a fully unsaturated side chain. Their structures were elucidated via spectroscopic methods including 1D, 2D NMR and HR-ESIMS. The absolute configurations were determined by the comparison of chemical shifts and optical rotation values with those of known ophiobolins. All compounds ( 1 - 9 ) were then evaluated for their cytotoxicity against six cancer cell lines, HCT-15, NUGC-3, NCI-H23, ACHN, PC-3 and MDA-MB-231. All the compounds showed potent cytotoxicity with GI 50 values ranging from 0.14 to 2.01 μM.

Background: Newly emergent and virulent strains of H7N9 avian influenza virus are rapidly spreading in China and threaten to invade Vietnam. We sought to introduce aerosol sampling for avian influenza viruses in Vietnam., Methods: During October 2017, National Institute for Occupational Safety and Health 2-stage aerosol samplers were assembled on a tripod and run for 4 hours. Concomitantly, up to 20 oropharyngeal (OP) swab samples were collected from chickens and ducks distanced at 0.2-1.5 m from each sampler., Results: The 3 weeks of sampling yielded 30 aerosol samples that were 90% positive for influenza A, by quantitative reverse-transcription polymerase chain reaction, and 116 OP swab sample pools (5 samples per pool) that were 47% positive. Egg cultures yielded 1 influenza A virus (not H5 or H7) from aerosol and 25 influenza A viruses from OP swab sample pools (5 were H5 positive). The association between positive sample types (over time and position) was strong, with 91.7% of positive OP pooled swab samples confirmed by positive aerosol samples and 81% of influenza A positive aerosol samples confirmed by positive OP swab samples., Conclusions: We posit that aerosol sampling might be used for early warning screening of poultry markets for novel influenza virus detection, such as H7N9. Markets with positive aerosol samples might be followed up with more focused individual bird or cage swabbing, and back-tracing could be performed later to locate specific farms harboring novel virus. Culling birds in such farms could reduce highly pathogenic avian influenza virus spread among poultry and humans., (© The Author(s) 2018. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

Porcine reproductive and respiratory syndrome (PRRS) is an important disease in pig production and is endemic in Vietnam. No nationwide studies have been carried out to understand the spread of PRRS in Vietnam. The main objective of this study was to identify the seasonal patterns and space-time clusters of PRRS from 2008 to 2016 using national surveillance data in Vietnam. A total of 614,219 cases were reported during the period. There was a seasonal pattern with single peak by region (except North Central Coast, showing double peaks in March and June). The seasonal plots from the Northern regions showed a higher peak between March and April, whereas the four regions from Southern part displayed a higher peak between June and August. Overall, outbreaks from the northern part of Vietnam tended to occur 3-4 months earlier than the southern part. When the spatial window was set at 50%, space-time cluster analysis found that the first cluster occurred in the Red River Delta (RRD) (radius: 82.17 km; ratios: 5.5; period: Mar-May/2010) and the second (radius: 50.8 km; ratios: 10.61; period: Aug-Oct/2011) in the Mekong River Delta (MRD) region. Four other clusters were observed in the central and Southern parts. Our findings might provide better insight into the distribution of clusters and temporal patterns of PRRS in Vietnam. This study may provide policy makers with valuable information on the hotspot areas and timing of outbreaks. Also, it identifies when and where national control program could be implemented more efficiently by targeting resources for the prevention and control of PRRS., (© 2019 The Authors. Transboundary and Emerging Diseases published by Blackwell Verlag GmbH.)

In spite of highly pathogenic avian influenza H5N1 vaccination campaigns for domestic poultry, H5N1 viruses continue to circulate in Vietnam. To estimate the prevalence of avian influenza virus in Vietnam, surveillance was conducted between November 2011 and February 2013. Genetic analysis of 312 highly pathogenic avian influenza H5 viruses isolated from poultry in Vietnam was conducted and possible genetic relationships with strains from neighboring countries were investigated. As previously reported, phylogenetic analysis of the avian influenza virus revealed two H5N1 HPAI clades that were circulating in Vietnam. Clade 1.1, related to Cambodian strains, was predominant in the southern provinces, while clade 2.3.2.1 viruses were predominant in the northern and central provinces. Sequence analysis revealed evidence of active genetic evolution. In the gene constellation of clade 2.3.2.1, genotypes A, B, and B(II) existed during the 2011/2012 winter season. In June 2012, new genotype C emerged by reassortment between genotype A and genotype B(II), and this genotype was predominant in 2013 in the northern and central provinces. Interestingly, enzootic Vietnamese clade 2.3.2.1C H5 virus subsequently reassorted with N2, which originated from wild birds, to generate H5N2 highly pathogenic avian influenza, which was isolated from duck in the northeast region. This investigation indicated that H5N1 outbreaks persist in Vietnam and cause genetic reassortment with circulating viruses. It is necessary to strengthen active influenza surveillance to eradicate highly pathogenic avian influenza viruses and sever the link between highly pathogenic avian influenza and other circulating influenza viruses., (© 2015 Poultry Science Association Inc.)

From the avian influenza virus (AIV) outbreaks and market surveillances in Vietnam during November 2011 and March 2012, a total of 196 AIV were isolated. Although H5N1 highly pathogenic avian influenza (HPAI) was the most prevalent subtype in Vietnam, 57 low pathogenic avian influenza (LPAI) viruses were identified from mainly domestic ducks and some chickens. Of note, various subtypes of LPAI viruses were isolated from domestic ducks in Vietnam: H3 (n = 16), H4 (n = 4), H6 (n = 24), H7 (n = 1), and H9 (n = 10). Geographically, the LPAI viruses were identified in different regions of Vietnam. Phylogenetic analysis of HA and NA genes in LPAIV in Vietnam showed that some H3 (group I) and H4 subtypes AIV clustered with the viruses of several Asian isolates from domestic poultry and wild birds. However, the H6, H9, and some H3 (group II and III) subtypes AIV were closely related to isolates from domestic poultry in Southern China. In addition, whereas the N2 and N6 subtypes AIV belonged to the Eurasian lineage, the N8 subtype AIV was classified to be both of Eurasian and American lineage. These findings revealed that the regional trade and wild birds play a key role transmission of LPAIV in domestic ducks in Vietnam. Further surveillance at the intercountry level is needed to understand the epidemiology of these viruses and to cope with emergence of novel AIV types.

Six field foot-and-mouth disease viruses (FMDVs), including four serotype O and two serotype Asia 1 strains, were collected from endemic outbreaks in 2005, 2006, and 2007 from four different provinces in Vietnam. The viruses were isolated and genetically characterized for their complete genomic sequences. The genetic analysis based on the complete genomic coding sequences revealed that the four serotype O FMDVs were related to each other, sharing 95.2% nucleotide (nt) identity and 97.5-97.6% amino acid (aa) identity. Genetic analysis and a phylogenetic tree, based on the VP1 gene of FMDV, showed that the four present Vietnamese serotype O strains have a high level of identity with other serotype O representatives of the Mya-98 lineage of the Southeast Asian (SEA) topotype. The four viruses were all clustered into the Mya-98 lineage of the SEA topotype, sharing 92.3-95.6% nt and 93.4-96.7% aa identity. This finding of the Mya-98 lineage was different from previous reports that the Vietnamese serotype O strains belonged to the Cam-94 lineage of the SEA topotype and two other topotypes, Middle East-South Asia (ME-SA) and Cathay. For the two serotype Asia 1 FMDVs, the genetic analysis based on the complete genomic coding sequences as well as on the VP1 gene revealed that they belonged to two genogroups, IV and V. Of note, the As1/VN/QT03/2007 strain of genogroup V, isolated in 2007, was very closely related to the pandemic Asia 1 strain which caused FMD outbreaks in China (Asia1/WHN/CHA/06, FJ906802) and Mongolia (Asia1/MOG/05, EF614458) in 2005, sharing 99.0-99.3% nt and 99.5-100% aa identity. In contrast, the second strain As1/VN/LC04/2005 of genogroup IV, isolated in 2005, was closely related to all referenced Vietnamese serotype Asia 1 strains found in the GenBank databases, sharing 86.4-100% nt and 90.9-100% aa identity with each. This study is the first description of the full-length genomic sequence of Vietnamese FMDV serotypes O and Asia 1 and may provide the evidence of the concurrent circulation of different serotypes and subtypes of FMDV in recent years in Vietnam., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Foot-and-mouth disease (FMD) is a major cause of endemic outbreaks in Vietnam in recent years. In this work, six serotype A foot-and-mouth disease viruses (FMDV), collected from endemic outbreaks during January and February of 2009 in four different provinces in Vietnam, were genetically characterized for their complete genome sequences. Genetic analysis based on the complete viral genome sequence indicated that they were closely related to each other and shared 99.0-99.8% amino acid (aa) identity. Genetic and deduced aa analysis of the capsid coding gene VP1 showed that the six Vietnamese strains were all classified into the genotype IX from a total of 10 major genotypes worldwide, sharing 98.1-100% aa identity each other. They were most closely related to the type A strains recently isolated in Laos (A/LAO/36/2003, A/LAO/1/2006, A/LAO/6/2006, A/LAO/7/2006, and A/LAO/8/2006), Thailand (A/TAI/2/1997 and A/TAI/118/1987), and Malaysia (A/MAY/2/2002), sharing 88.3-95.5% nucleotide (nt) identities. In contrast, Vietnamese type A strains showed low nt identities with the two old type A FMDVs, isolated in 1960 in Thailand (a15thailand iso43) and in 1975 in the Philippines (aphilippines iso50), ranging from 77.3 to 80.9% nt identity. A multiple alignment based on the deduced amino acid sequences of the capsid VP1 coding gene of type A FMDV revealed three amino acid substitutions between Vietnamese strains and the strains of other Southeast Asian countries (Laos, Thailand, Malaysia, and the Philippines). Alanine was replaced by valine at residue 24, asparagine by arginine at residue 85, and serine by threonine at residue 196. Furthermore, type A FMDV strains recently isolated in Vietnam, Laos, Thailand, and Malaysia all have one amino acid deletion at residue 140 of the capsid VP1 protein compared with the two old type A FMDV strains from Thailand and the Philippines as well as most other type A representatives worldwide. This article is the first to report on the comprehensive genetic characterization of type A FMDV circulating in Vietnam., (Copyright (c) 2010 Elsevier B.V. All rights reserved.)