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Title: An integrative analysis of foot-and-mouth disease virus carriers in Vietnam achieved through targeted surveillance and molecular epidemiology

item DE CARVALHO FERREIRA, HELENA - Oak Ridge Institute For Science And Education (ORISE)
item Pauszek, Steven
item LUDI, ANNA - Pirbright Laboratory
item HUSTON, CARLA - Mississippi State University
item Pacheco Tobin, Juan
item DUNG, DO HUU - Ministry Of Agriculture And Rural Development (MARD)
item THUY, NGUYEN THU - Ministry Of Agriculture And Rural Development (MARD)
item VU, LE TRI - Ministry Of Agriculture And Rural Development (MARD)
item THO, NGUYEN DANG - Ministry Of Agriculture And Rural Development (MARD)
item LONG, NGO THANH - Ministry Of Agriculture And Rural Development (MARD)
item Rodriguez, Luis
item Arzt, Jonathan

Submitted to: Transboundary and Emerging Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2015
Publication Date: 9/24/2015
Publication URL:
Citation: De Carvalho Ferreira, H.C., Pauszek, S.J., Ludi, A., Huston, C.L., Pacheco Tobin, J., Dung, D., Thuy, N., Vu, L., Tho, N., Long, N., Rodriguez, L.L., Arzt, J. 2015. An integrative analysis of foot-and-mouth disease virus carriers in Vietnam achieved through targeted surveillance and molecular epidemiology. Transboundary and Emerging Diseases. doi: 10.1111/tbed.12403.

Interpretive Summary: Foot-and-mouth disease (FMD) is one of the most feared and most contagious diseases affecting domestic livestock and some wildlife species. A hardy and highly variable virus called FMD virus (FMDV) which exists in seven different groups and causes the disease is present throughout much of Asia. In Vietnam, livestock often suffer from FMD and may also be carriers of the virus without showing signs of disease. The current study utilized a multidisciplinary approach to obtain a better understanding of the spread patterns of FMDV across Vietnam. The data shows nearly one fourth (22.3 percent) of ruminants in Vietnam had been exposed to the virus, and 2.4 percent still carried FMDV. By analyzing the virus’s genetic material of 109 viruses obtained though this study researchers found most were from the group called serotype O. Most viruses from outbreaks and all viruses from carriers (total of 92 viruses) belonged to one specific subgroup of serotype O (called ME-SA/PanAsia lineage) that circulates in large parts of South East Asia. This finding suggests that between 2010 and 2013 the main lineage circulating in Vietnam were similar to those circulating in neighboring countries. Viruses from carrier animals were very similar to viruses from outbreaks dating from 2010 to 2013.

Technical Abstract: A multidisciplinary, molecular and conventional epidemiological approach was applied to an investigation of endemic foot-and-mouth disease in Vietnam. Within the study space, it was found that 22.3 percent of sampled ruminants had previously been infected with FMD virus (FMDV) and that 2.4 percent were persistent asymptomatic carriers. Descriptive data collected from targeted surveillance and a farm questionnaire showed a significantly lower risk of FMD virus (FMDV) infection for dairy farms and higher risk for farms with larger capacity and/or history of infection in 2010. Furthermore, while buffalo had the highest risk of being FMDV-infected, beef cattle had the highest carrier risk, suggesting lower susceptibility of buffalo to persistent FMDV infection. The variables location and age were also significantly associated with infection and carrier risk. Complementing the surveillance data, VP1 sequences of FMDV field strains from Vietnam collected from oropharyngeal fluid (OPF) of carriers between 2012 and 2013 (N=27), and of FMDV outbreaks from 2009-2013 (N=79) were compared by phylogenetic analysis. From 106 sequenced viruses, eight were serotype A (Asia/Sea-97 lineage) viruses, including two apparent novel introductions, and the remainder were serotype O (N=98). Within serotype O, while six viruses were of the O SEA/Mya-98 lineage, most were of the O ME-SA/PanAsia lineage (N=92), including all isolates from carriers. FMDV from carriers collected in 2012 or 2013 were related to FMDV isolates from 2010-2013 outbreaks. Temporal analysis suggests that within the study period, the dominant lineage of serotype O in Vietnam shifted from SEA/Mya-98 to ME-SA/PanAsia.