Phylodynamics of epidemic and asymptomatic foot-and-mouth disease in Vietnam 2010-2014

Authors: BRITO, BARBARA - Oak Ridge Institute For Science And Education (ORISE); Pauszek, Steven; ESCHBAUMER, MICHAEL - Oak Ridge Institute For Science And Education (ORISE); STENFELDT, CAROLINA - Oak Ridge Institute For Science And Education (ORISE); DE CARVALHO FERREIRA, HELENA - Oak Ridge Institute For Science And Education (ORISE); VU, LE - Ministry Of Agriculture And Rural Development (MARD); PHUONG, NGUYEN - Ministry Of Agriculture And Rural Development (MARD); HOANG, BUI - Ministry Of Agriculture And Rural Development (MARD); THO, NGUYEN - National Center For Veterinary Diagnostics; DONG, PHAM - Ministry Of Agriculture And Rural Development (MARD); MINH, PHAN - Ministry Of Agriculture And Rural Development (MARD); LONG, NGO - Ministry Of Agriculture And Rural Development (MARD); DUNG, DO - Ministry Of Agriculture And Rural Development (MARD); Rodriguez, Luis; Arzt, Jonathan

Submitted to: Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2017
Publication Date: 4/13/2017
Citation: Brito, B., Pauszek, S.J., Eschbaumer, M., Stenfeldt, C., De Carvalho Ferreira, H., Vu, L.T., Phuong, N.T., Hoang, B.H., Tho, N.D., Dong, P.V., Minh, P.Q., Long, N.T., Dung, D.H., Rodriguez, L.L., Arzt, J. 2017. Phylodynamics of epidemic and asymptomatic foot-and-mouth disease in Vietnam 2010-2014. Veterinary Research. 48:24.

Interpretive Summary: Foot-and-mouth disease (FMD) is a highly contagious disease of livestock, which is not present in the U.S., but is present in Africa, Asia and South America. This viral disease can cause devastating economic losses if introduced into a country. The genetic changes that occur in the virus can leave a signal that helps understand evolution in different hosts species and in different geographic areas. In this study, we used genetic information of FMD virus collected in different regions of Vietnam between 2010 and 2014 from cattle, water buffalo and pigs. The objective of this study was to use genetic information to understand transmission (1) between Vietnam regions, (2) between pigs, buffalo and cattle and (3) between infected animals with clinical disease and apparently healthy animals. Our results support the transmission from cattle to pigs and buffalo, and from pigs to cattle. We also found that more genetic changes occur in viruses from asymptomatic (silent) hosts than those from obviously diseased animals. This information will help to protect the USA homeland if FMD is ever introduced.

Technical Abstract: Foot-and-mouth disease virus (FMDV) is endemic in Vietnam, a country that plays an important role in animal trade within Southeast Asia. The large populations of buffalo, cattle and pigs (all FMDV susceptible species) in Vietnam are important components of food production and of the national livelihood. In the current study, we investigated the phylogeny of FMDV O/PanAsia in Vietnam, reconstructing the virus’ ancestral host species (pig, cattle or buffalo), clinical stage (clinical or asymptomatic carrier) and geographical location. Phylogenetic divergence time estimation and character state reconstruction analyses suggest that movements of viruses between species differ. While inferred transmissions from cattle to buffalo and pigs and from pigs to cattle are well-supported, transmission from buffalo to other species, and from pigs to buffalo may be less frequent. Geographical movements of FMDV O/PanAsia virus appears to occur in all directions within the country, with the South Central Coast and the Northeast regions playing a more important role in FMDV O/PanAsia spread. Genetic selection of variants with changes at specific sites within FMDV VP1 coding region was different depending on host groups analyzed. Overall positive selection was greater in pigs compared to cattle and buffalo, whereas a higher number of genetic sites under positive selection were detected in persistently infected animals compared to viruses collected from clinically diseased animals. These results provide novel insights to understand FMDV evolution and its association with viral spread within endemic countries. These findings may support animal health organizations in their endeavor to design animal disease control strategies in response to outbreaks.