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United States Department of Agriculture

Agricultural Research Service

Related Topics


Location: Foreign Animal Disease Research

2013 Annual Report

1a. Objectives (from AD-416):
1. Determine the molecular epidemiology of FMDV in local livestock in Vietnam including cattle, buffaloes and pigs. 2. Better understand the transmission mechanism of FMDV from persistently infected to susceptible local livestock in natural setting. 3. Enhance strategies for identification of persistently infected animals using new technology. Amendment 1: 4. Vaccine matching between field strains and current vaccine viruses will be carried out to assess efficacy against currently circulating strains.

1b. Approach (from AD-416):
1. Acute samples: A systematic FMD monitoring program to determine the molecular epidemiology of FMDV in local livestock in Vietnam will be initiated. All FMD cases from all species reported to the Department of Animal Health (DAH) and FMD-suspected animals at infected area quarantine stations will be included in the program. Epithelial or vesicular fluid, lesions swabs, sera, oral swab, and oropharyngeal fluid (probing sample) will be collected from clinically infected or suspected animals on the premises. All samples will be sent to the laboratory within 24 hours. Sera will be kept at -20oC until tested using various detection methods including liquid phase blocking ELISA (LP ELISA) and non structural protein ELISA (NSP ELISA), realtime RT-PCR and virus isolation. All samples will be sent to the Plum Island Animal Disease Center (PIADC) for collaborative studies. Information including animal species, location of infected premise (GPS coordinates), address of the premise, number of affected animals, number of susceptible animals, movement history, vaccination history, purchase history, husbandry management, etc will be collected at the time of sample collection and stored in predesigned computer database. 2. A longitudinal field study will be conducted to determine viral and host genomic factors influencing viral persistence in local livestock in Vietnam including cattle, buffaloes, goats, and pig, and to better understand persistence mechanism in these species. Individual animals with well documented persistent infections will be purchased and slaughtered to collect relevant tissues for virological and pathological investigations. A longitudinal collection of samples (sera, oral swabs, and oropharyngeal samples) will be done from all carrier and susceptible animals at the beginning of the study, and then followed up first 30 days and then 3-6 months interval for a period of two years. All samples will be sent to the DAH within 24 hours. Sera will be kept at -20oC until tested using ELISA. Oral swabs will be kept at -80oC until tested using realtime RT-PCR and virus isolation. Oropharyngeal fluids will be kept at -80oC until tested using realtime RT-PCR and virus isolation. Oropharyngeal fluids will be kept at -80oC and used for sequencing of whole FMD genome. Apart from testing, all samples will be stored at an appropriate condition for later reference. 3. Various pen-side and laboratory based diagnostic tests will be evaluated during field studies. Analyses will be performed to evaluate and compare the performance of the different diagnostic methods for detection of FMDV in clinically and non-clinically infected animals, in various stages of carriers, and during the early state of infection in susceptible animals. Amendment 1: 4. Sera from cattle vaccinated with different strains of serotype O will be sent to ARS, PIADC for vaccine matching. These Vietnamese field strains will be used for this objective. In accorance to the OIE Terrestrial Manual, a relationship coefficient will be determined between the vaccine viruses and field viruses and the resulting value will be assessed as to whether there is a vaccine match.

3. Progress Report:
Sample collection continued from cattle and buffalo which were previously determined to be asymptomatic carriers of FMDV. Many of these animals were enrolled in either a longitudinal transmission study in Long An province of southern Vietnam or in a necropsy, tissue analysis study in northern Vietnam. The principal investigator from ARS, PIADC traveled to Vietnam during FY 2013 where he conducted necropsies and collected samples from some of the previously diagnosed, FMDV-positive cattle and buffalo in northern Vietnam. He also visited southern Vietnam and visited ongoing longitudinal study sites. Additional support for this project was provided by Mississippi State University (MSU) collaborators who traveled to Vietnam to follow up on surveillance activities and help with data analysis. Two shipments containing field samples were received at PIADC from DAH. Samples included archived outbreak viruses from 2010-2012 and animal samples from the necropsy study in the north. Full length sequences were obtained from most of the outbreak samples. Numerous Sequence analyses were performed to determine viral strains. In addition, preliminary optimization of methods for sequencing samples with “next generation” sequencing technologies was performed. Phylogenetic trees were constructed to ascertain viral relationships. No technologies were transferred during FY 2013. No publications were prepared during this time.

4. Accomplishments

Last Modified: 06/25/2017
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